SPOTTSWOOD W. ROBINSON, III, Circuit Judge:

Indicted for second-degree murder,1 and convicted by a jury of manslaughter2 as a lesser included offense,3 Ben*1225nie L. Peterson urges three grounds for reversal. He asserts, first that from the voir dire examination of the veniremen from among whom the jury was selected, the trial judge erroneously excluded three questions which he had requested.4 He contends, next, that the evidence was legally insufficient to establish his guilt of manslaughter, and that in consequence the judge erred in denying his motion for a judgment of acquittal.5 He complains, lastly, that the judge twice erred in the instructions given the jury in relation to his claim that the homicide was committed in self-defense. One error alleged was an instruction that the jury might consider whether Peterson was the aggressor in the altercation that immediately foreran the homicide.6 The other was an instruction that a failure by Peterson to retreat, if he could have done so without jeopardizing his safety, might be considered as a circumstance bearing on the question whether he was justified in using the amount of force which he did.7 After careful study of these arguments in light of the trial record, we affirm Peterson’s conviction.

I

The events immediately preceding the homicide are not seriously in dispute.8 The version presented by the Government’s evidence follows. Charles Keitt, the deceased, and two friends drove in Keitt’s car to the alley in the rear of Peterson’s house to remove the windshield wipers from the latter’s wrecked car.9 While Keitt was doing so, Peterson came out of the house10 into the back yard to protest. After a verbal exchange,11 Peterson went back into the house, obtained a pistol, and returned to the yard.12 In the meantime, Keitt had reseated himself in his car, and he and his companions were about to leave.13

Upon his reappearance in the yard, Peterson paused briefly to load the pistol.14 “If you move,” he shouted to Keitt, “I will shoot.” He walked to a point in the yard slightly inside a. gate in the rear fence and, pistol in hand, said, “If you come in here I will kill you.” Keitt alighted from his car, took a few steps toward Peterson and exclaimed, “What the hell do you think you are going to do with that?”15 Keitt then made an about-face, walked back to *1226his car and got a lug wrench. With the wrench in a raised position, Keitt advanced toward Peterson, who stood with the pistol pointed toward him. Peterson warned Keitt not to “take another step” and, when Keitt continued onward shot him in the face from a distance of about ten feet.16 Death was apparently instantaneous. Shortly thereafter, Peterson left home and was apprehended 20-odd blocks away.

This description of the fatal episode was furnished at Peterson’s trial by four witnesses for the Government.17 Peterson did not testify or offer any evidence, but the Government introduced a statement which he had given the police after his arrest,18 in which he related a somewhat different version. Keitt had removed objects from his car before, and on the day of the shooting he had told Keitt not to do so. After the initial verbal altercation, Keitt went to his car for the lug wrench, so he, Peterson, went into his house for his pistol. When Keitt was about ten feet away, he pointed the pistol “away of his right shoulder;” adding that Keitt was running toward him, Peterson said he “got scared and fired the gun. He ran right into the bullet.” “I did not mean to shoot him,” Peterson insisted, “I just wanted to scare him.”

At trial, Peterson moved for a judgment of acquittal19 on the ground that as a matter of law the evidence was insufficient to support a conviction. The trial judge denied the motion.20 After receiving instructions which in two respects are challenged here,21 the jury returned a verdict finding Peterson guilty of manslaughter. Judgment was entered conformably with the verdict, and this appeal followed.

II

Shortly before the selection of the jury got under way, Peterson’s counsel requested the trial judge to address three questions to the prospective jurors on their voir dire examination. Specifically, counsel wanted them queried as to whether any venireman believed that an inference of guilt should be drawn from the fact that Peterson had been indicted; whether any felt that in the instance of a fatality, “someone ha[s] to pay for” the taking of life; and whether any had an innate fear of firearms that might cause him to view with apprehension a person who possessed or used one. The judge denied the request in toto, and the denial is now assigned as error.

Examination of prospective jurors is a step vital to the fairness of jury trials. The information elicited on voir dire serves the dual purpose of aiding counsel in the exercise of challenges and the court in the determination of competence to serve.22 Without knowledge bearing on the qualifications of the veniremen, neither function can *1227be performed intelligently.23 To the extent that the examinatorial process is deficient, the impartiality of the jury could be compromised.24

To achieve its wholesome goals, voir dire examination must be given a wise and liberal scope.25 Reasonable latitude must be indulged to inquiry into attitudes and inclinations in order to assure the objectivity of the jurors ultimately chosen.26 To be sure, the trial judge retains a broad discretion as to the questions which may be addressed.27 But, as the Supreme Court has declared, “[t]he exercise of this discretion, and the restriction upon inquiries at the request of counsel, [are] subject to the essential demands of fairness.”28

Peterson argues that the refusal of the three questions he submitted constituted reversible error. The judge’s ruling was bottomed on the premise that the purposes for which the questions were requested would be accomplished in other ways.29 The standard for our review of that ruling is whether tbe judge’s action exceeded the bounds of discretion to Peterson’s prejudice.30 We find it unnecessary to consider whether the questions were proper for, in the circumstances presented, we are satisfied that their exclusion could not have operated detrimentally to him.

Near the outset of the voir dire examination, the judge instructed the venire*1228men that the indictment was not evidence in the case, but only the means by which Peterson was notified of the charge against him. This was tantamount to an admonition that no basis for an inference of guilt was afforded by the fact that Peterson had been indicted — the subject of Peterson’s first question. The judge also paraphrased the charge made against Peterson by the indictment,31 and from that the veniremen knew that a fatality had been wrought by the discharge of a firearm —the topics upon which Peterson’s other two questions focused. And, very importantly, the judge, near the conclusion of the examination, inquired as to whether there was “any reason whatsoever why anyone . . . would prefer not to sit in this case or . any reason whatsoever why you do not feel you would be a good . . . fair and impartial juror?” That inquiry called upon each prospective juror, on his oath, to respond if he felt that any aspect of the case, including those of which the judge had informed, might affect his impartiality.

We perceive no prejudice resultant from the denial of Peterson’s request. The judge posed a general question that should have elicited instances of bias, if any at all existed, on the part of the veniremen.32 On the other hand, none of the questions which Peterson proposed —concerning the indictment, the gun or the fatality — related to a matter as to which it has become evident, through experience with juries, that there are strong feelings in the community apt to interfere with a capacity for fair and impartial verdicts, including those on claims of self-defense. Moreover, Peterson made no effort to lay a foundation for his questions by showing either that any such predilections were likely to be encountered, or that his questions were “reasonably calculated to discover an actual and likely source of prejudice, rather than pursue a speculative will-o-the-wisp.”33 In these circumstances, we decline to disturb the judge’s ruling.

Ill

More than two centuries ago, Blackstone, best known of the expositors of the English common law, taught that “all homicide is malicious, and of course, amounts to murder, unless justified by the command or permission of the law; excused on the account of accident or self-preservation; or alleviated into manslaughter, by being either the involuntary consequence of some act not strictly lawful, or (if voluntary) occasioned by some sudden and sufficiently violent provocation.34

Tucked within this greatly capsulized schema of the common law of homicide is the branch of law we are called upon to administer today. No issue of justifiable homicide, within Blackstone’s definition is involved.35 But Peterson’s con*1229sistent position is that as a matter of law his conviction of manslaughter — alleviated homicide — was wrong, and that his act' was one of self-preservation— excused homicide. The Government, on the other hand, has contended from the beginning that Keitt’s slaying fell outside the bounds of lawful self-defense. The questions remaining for our decision inevitably track back to this basic dispute.

Self-defense, as a doctrine legally exonerating the taking of human life, is as viable now as it was in Blackstone’s36 time, and in the case before us the doctrine is invoked in its purest form.37 But “[t]he law of self-defense is a law of necessity38 the right of self-defense arises only when the necessity begins, and equally ends with the necessity ;39 and never must the necessity be greater than when the force employed defensively is deadly.40 The “necessity must bear all semblance of reality, and appear to admit of no other alternative, before taking life will be justifiable as excusable.” 41 Hinged on the exigencies of self-preservation, the doctrine of homicidal self-defense emerges from the body of the criminal law as a limited though important exception to legal outlawry of the arena of self-help in the settlement of potentially fatal personal conflicts.

So it is that necessity is the pervasive theme of the well defined conditions which the law imposes on the right to kill or maim in self-defense. There must have been a threat, actual or apparent, of the use of deadly force against the defender.42 The threat must have been unlawful43 and immediate.44 *1230The defender must have believed that he was in imminent peril of death or serious bodily harm,45 and that his response was necessary . to save himself therefrom.46 These beliefs must not only have been honestly entertained, but also objectively reasonable in light of the surrounding circumstances.47 It is clear that no less than a concurrence of these elements will suffice.

Here the parties’ opposing contentions focus on the roles of two further considerations. One is the provoking of the confrontation by the defender. The other is the defendant’s failure to utilize a safe route for retreat from the confrontation. The essential inquiry, in final analysis, is whether and to what extent the rule of necessity may translate these considerations into additional factors in the equation. To these questions, in the context of the specific issues raised, we now proceed.

IV

The trial judge’s charge authorized the jury, as it might be persuaded, to convict Peterson of second-degree murder or manslaughter, or to acquit by reason of self-defense. On the latter phase of the case, the judge instructed that with evidence of self-defense present, the Government bore the burden of proving beyond a reasonable doubt that Peterson did not act in self-defense; and that if the jury had a reasonable doubt as to whether Peterson acted in self-defense, the verdict must be not guilty. The judge further instructed that the circumstances under which Peterson acted, however, must have been such as to produce a reasonable belief that Keitt was then about to kill him or do him serious bodily harm, and that deadly force was necessary to repel him. In determining whether Peterson used excessive force in defending himself, the judge said, the jury could consider all of the circumstances under which he acted.

These features of the charge met Peterson’s approval, and we are not summoned to pass on them. There were, however, two other aspects of the charge to which Peterson objected, and which are now the subject of vigorous controversy. The first of Peterson’s complaints centers upon an instruction that the right to use deadly force in self-defense is not ordinarily available to one who provokes a conflict or is the aggressor in it. Mere words, the judge explained, do not constitute provocation or aggression; and if Peterson precipitated the áltereation but thereafter withdrew from it in good faith and so informed Keitt by words or acts, he was justified in using deadly force to save himself from imminent danger or death or grave bodily harm. And, the judge added, even if Keitt was the aggressor and Peterson was justified in defending him*1231self, he was not entitled to use any greater force than he had reasonable ground to believe and actually believed to be necessary for that purpose. Peterson contends that there was no evidence that he either caused or contributed to the conflict, and that the instructions on that topic could only misled the jury.

It has long been accepted that one cannot support a claim of self-defense by a self-generated necessity to kill.48 The right of homicidal self-defense is granted only to those free from fault in the difficulty; it is denied to slayers who incite the fatal attack, encourage the fatal quarrel or otherwise promote the necessitous occasion for taking life.49 The fact that the deceased struck the first blow, fired the first shot or made the first menacing gesture does not legalize the self-defense claim if in fact the claimant was the actual provoker.50 In sum, one who is the aggressor in a conflict culminating in death cannot invoke the necessities of self-preservation. Only in the event that he communicates to his adversary his intent to withdraw and in good faith attempts to do so is he restored to his right of self-defense 51

This body of doctrine traces its origin to the fundamental principle that a killing in self-defense is excusable only as a matter of genuine necessity.52 Quite obviously, a defensive killing is unnecessary if the occasion for it could have been averted, and the roots of that consideration run deep with us. A half-century ago, in Laney v. United States,53 this court declared

that, before a person can avail himself of the plea of self-defense against the charge of homicide, he must do everything in his power, consistent with his safety, to avoid the danger and avoid the necessity of taking life. If one has reason to believe that he will be attacked, in a manner which threatens him with bodily injury, he must avoid the attack if it is possible to do so, and the right of self-defense does not arise until he has done everything in his power to prevent its necessity.54

And over the many years since Laney, the court has kept faith with its precept.55

*1232In the case at bar, the trial judge’s charge fully comported with these governing principles. The remaining question, then, is whether there was evidence to make them applicable to the case. A recapitulation of the proofs shows beyond peradventure that there was.

It was not until Peterson fetched his pistol and returned to his back yard that his confrontation with “Keitt took on a deadly cast. Prior to his trip into the house for the gun, there was, by the Government’s evidence, no threat, no display of weapons, no combat. There was an exchange of verbal aspersions56 and a misdemeanor57 against Peterson’s property58 was in progress but, at this juncture, nothing more. Even if Peterson’s post-arrest version59 of the initial encounter were accepted — his claim that Keitt went for the lug wrench before he armed himself —the events which followed bore heavily on the question as to who the real aggressor was.60

The evidence is uncontradicted that when Peterson reappeared in the yard with his pistol,61 Keitt was about to depart the scene. Richard Hilliard testified that after the first argument, Keitt reentered his car and said “Let’s go.” This statement was verified by Ricky Gray, who testified that Keitt “got in the car and . . . they were getting ready to go;” he, too, heard Keitt give the direction to start the car. The uncontroverted fact that Keitt was leaving shows plainly that so far as he was concerned the confrontation was ended. It demonstrates just as plainly *1233that even if he had previously been the aggressor, he no longer was.

Not so with Peterson, however, as the undisputed evidence made clear.62 Emerging from the house with the pistol, he paused in the yard to load it,63 and to command Keitt not to move. He then walked through the yard to the rear gate and, displaying his pistol, dared Keitt to come in, and threatened to kill him if he did. While there appears to be no fixed rule on the subject, the cases hold, and we agree, that an affirmative unlawful act reasonably calculated to produce an affray foreboding injurious or fatal consequences is an aggression which, unless renounced,64 nullifies the right of homicidal self-defense.65 We cannot escape the abiding conviction that the jury could readily find Peterson’s challenge to be a transgression of that character.

The situation at bar is not unlike that presented in Laney.66 There the accused, chased along the street by a mob threatening his life, managed to escape through an areaway between two houses. In the back yard of one of the houses, he checked a gun he was carrying and then returned to the areaway. The mob beset him again, and during an exchange of shots one of its members was killed by a bullet from the accused’s gun. In affirming a conviction of manslaughter, the court reasoned:

It is clearly apparent . . . that, when defendant escaped from the mob into the back yard ... he was in a place of comparative safety, from which, if he desired to go home, he could have gone by the back way, as he subsequently did. The mob had turned its attention to a house on the opposite side of the street. According to Laney’s testimony, there was shooting going on in the street. His appearance on the street at that juncture could mean nothing but trouble for him. Hence, when he adjusted his gun and stepped out into the areaway, he had every reason to believe that his presence there would provoke trouble. We think his conduct in adjusting his revolver and going into the areaway was such as to deprive him of any right to invoke the plea of self-defense.67

Similarly, in Rowe v. United States,68 the accused was in the home of friends when an argument, to which the friends became participants, developed in the street in front. He left, went to his nearby apartment for a loaded pistol and returned. There was testimony that he then made an insulting comment, drew the pistol and fired a shot into the ground. In any event, when a group of five men began to move toward him, he began to shoot at them, killing two, and wounding a third. We observed that the accused “left an apparently safe haven to arm himself and return to the scene,” 69 and that “he inflamed the situation with his words to the men gathered there, even though he could have *1234returned silently to the safety of the [friends’] porch.” 70 We held that

[t]hese facts could have led the jury to conclude that [the accused] returned to the scene to stir up further trouble, if not actually to kill anyone, and that his actions instigated the men into rushing him. Self-defense may not be claimed by one who deliberately places himself in a position where he has reason to believe “his presence . . . would provoke trouble.” 71

We noted the argument “that a defendant may claim self-defense if he arms himself in order to proceed upon his normal activities, even if he realizes that danger may await him”;72 we responded by pointing out “that the jury could have found that the course of action defendant here followed was for an unlawful purpose."73 We accordingly affirmed his conviction of manslaughter over his objection that an acquittal should have been directed.74

We are brought much the readier to the same conclusion here. We think the evidence plainly presented an issue of fact as to whether Peterson’s conduct was an invitation to and provocation of the encounter which ended in the fatal shot. We sustain the trial judge’s action in remitting that issue for the jury’s determination.

V

The second aspect of the trial judge’s charge as to which Peterson asserts error concerned the undisputed fact that at no time did Peterson endeavor to retreat from Keitt’s approach with the lug wrench. The judge instructed the jury that if Peterson had reasonable grounds to believe and did believe that he was in imminent danger of death or serious injury, and that deadly force was necessary to repel the danger, he was required neither to retreat nor to consider whether he could safely retreat. Rather, said the judge, Peterson was entitled to stand his ground and use such force as was reasonably necessary under the circumstances to save his life and his person from pernicious bodily harm. But, the judge continued, if Peterson could have safely retreated but did not do so, that failure was a circumstance which the jury might consider, together with all others, in determining whether he went further in repelling the danger, real or apparent, than he was justified in going.

Peterson contends that this imputation of an obligation to retreat was error, even if he could safely have done so. He points out that at the time of the shooting he was standing in his own yard, and argues he was under no duty to move. We are persuaded to the conclusion that in the circumstances presented here, the trial judge did not err in giving the instruction challenged.

Within the common law of self-defense there developed the rule of “retreat to the wall,”75 which ordinarily forbade the use of deadly force by one to whom an avenue for safe retreat was open.76 This doctrine was but an application of the requirement of strict necessity to excuse the taking of human life,77 and was designed to insure the existence of that necessity. Even the innocent victim of a vicious assault had to elect a safe re*1235treat, if available, rather than resort to defensive force which might kill or seriously injure.78

In a majority of American jurisdictions, contrarily to the common law rule, one may stand his ground and use deadly force whenever it seems reasonably necessary to save himself.79 While the law of the District of Columbia on this point is not entirely clear, it seems allied with the strong minority adhering to the common law. In 1856, the District of Columbia Criminal Court ruled that a participant in an affray “must endeavor to retreat, that is, he is obliged to retreat, if he can safely.”80 The court added that “[a] man may, to be sure, decline a combat when there is no existing or apparent danger, but the retreat to which the law binds him is that which is the consequence.”81 In a much later era this court, adverting to necessity as the soul of homicidal self-defense,82 declared that “no necessity for killing an assailant can exist, so long as there is a safe way open to escape the conflict.”83 Moreover, the common law rule of strict necessity pervades the District concept of pernicious self-defense,84 and we cannot ignore the inherent inconsistency of an absolute no-retreat rule. Until such time as the District law on the subject may become more definitive,85 we accept these precedents as ample indication that the doctrine of retreat persists.

That is not to say that the retreat rule is without exceptions. Even at common law it was recognized that it was. not completely suited to all situations. Today it is the more so that its precept must be adjusted to modern conditions nonexistent during the early development of the common law of self-defense.86 One restriction on its operation comes to the fore when the circumstances apparently foreclose a withdrawal with safety.87 The doctrine of retreat *1236was never intended to enhance the risk to the innocent; its proper application has never required a faultless victim to increase his assailant’s safety at the expense of his own. On the contrary, he could stand his ground and use deadly force otherwise appropriate if the alternative were perilous, or if to him it reasonably appeared to be.88 A slight variant of the same consideration is the principle that there is no duty to retreat from an assault producing an imminent danger of death or grievous bodily harm.89 “Detached reflection cannot be demanded in the presence of an uplifted knife,” 90 nor is it “a condition of immunity that one in that situation should pause to consider whether a reasonable man might not think it possible to fly with safety or to disable his assailant rather than to kill him.” 91

The trial judge’s charge to the jury incorporated each of these limitations on the retreat rule. Peterson, however, invokes another — the so-called “castle” doctrine.92 It is well settled that one who through no fault of his own is attacked in his home is under no duty to retreat therefrom.93 The oft-repeated expression that “a man’s home is his castle” reflected the belief in olden days that there were few if any safer sanctuaries than the home.94 The “castle” exception, moreover, has been extended by some courts to encompass the occupant’s presence within the curtilage outside his dwelling.95 Peterson reminds us that when he shot to halt *1237Keitt’s advance, he was standing in his yard and so, he argues, he had no duty to endeavor to retreat.

Despite the practically universal acceptance of the “castle” doctrine in American jurisdictions wherein the point has been raised,96 its status, in the District of Columbia has never been squarely decided.97 But whatever the fate of the doctrine in the District law of the future,98 it is clear that in absolute form it was inapplicable here. The right of self-defense, we have said, cannot be claimed by the aggressor in an affray so long as he retains that unmitigated role.99 It logically follows that any rule of no-retreat which may protect an innocent victim of the affray would, like other incidents of a forfeited right of self-defense, be unavailable to the party who provokes or stimulates the conflict. Accordingly, the law is well settled that the “castle” doctrine can be invoked only by one who is without fault in bringing the conflict on.100 That, we think, is the critical consideration here.

We need not repeat our previous discussion of Peterson’s contribution to the altercation which culminated in Keitt’s death.101 It suffices to point out that by no interpretation of the evidence could it be said that Peterson was blameless in the affair.102 And while, of course, it was for the jury to assess the degree of fault,103 the evidence well nigh dictated the conclusion that it was substantial.

The only reference in the trial judge’s charge intimating an affirmative duty to retreat104 was the instruction that a failure to do so, when it could have been done safely, was a factor in the totality of the circumstances which the jury might consider in determining whether the force which he employed was excessive.105 We cannot believe that any jury was at all likely to view Peterson’s *1238conduct as irreproachable. We conclude that for one who, like Peterson, was hardly entitled to fall back on the “castle” doctrine of no retreat, that instruction cannot be just cause for complaint.

VI

As we have stated, Peterson moved for a judgment of acquittal at trial, and in this court renews his contention that the evidence was insufficient to support a conviction of manslaughter.106 His position is that the evidence, as a matter of law, established a right to use deadly force in self-defense. In considering that contention, we must accept the evidence “in the light most favorable to the Government, making full allowance for the right of the jury to draw justifiable inferences of fact from the evidence adduced at trial and to assess the credibility of the witnesses before it.”107 We have already concluded that the evidence generated factual issues as to the effect, upon Peterson’s self-defense claim, of his aggressive conduct and his failure to ■retreat.108 By the same token, the ultimate question of guilt or innocence of culpable homicide was one for the jury to decide. The jury resolved the question in favor of guilt, and we perceive no basis for disturbing its decision. Nor, in the circumstances here, is there a ground for impugning its verdict that the grade of Peterson’s offense was manslaughter.109

The judgment of conviction appealed from is accordingly

Affirmed.

OPINION

MATTHEWS, Justice.

Shortly after midnight on May 22, 1976, Dale Nelson drove his four-wheel drive truck onto a side road off the Steese Highway near mile 68. His truck became bogged down in a marshy area about 250 feet off the highway. Nelson testified that he was afraid the truck might tip over in the soft ground. He and his two companions, Lynnette Stinson and Carl Thompson, spent an hour unsuccessfully trying to free the vehicle. At about 1:00, Nelson began walking with Stinson down the highway. An acquaintance drove by and offered to help, but was unable to render much assistance. He then drove Nelson and Stinson to a Highway Department Yard where heavy equipment was parked. The yard was *978marked with “no-trespassing” signs. After waiting several hours for someone to come by, they decided to take a dump truck and use it to pull out Nelson’s vehicle. The dump truck also became stuck.

At approximately 10:00 that morning a man identified only as “Curly” appeared. His vehicle was also stuck further down the highway. Curly offered to assist Nelson. They returned to the heavy equipment yard and took a front-end loader, which they used to free the dump truck. They then used the dump truck to free Curly’s car. The dump truck was returned to the equipment yard, but when Nelson attempted to use the front-end loader to free his own truck the front-end loader also became bogged down.

Frustrated and tired after twelve hours of attempting to free his vehicle, Nelson and his companions quit and went to sleep. Two of them slept in a tent. One of them went to sleep in the truck. They were awakened by a Highway Department employee, who placed them under citizen’s arrest.

Considerable damage was done to both the front-end loader and the dump truck as a result of Nelson’s attempt to free his truck.1 Ultimately, the truck was pulled from the mud three days later. Nelson was convicted in district court of reckless destruction of personal property in violation of AS 11.20.515(b)2 and joyriding in violation of AS 28.35.010.3 This conviction was affirmed on appeal to the superior court.

The sole question presented is whether the jury was properly instructed on the defense of necessity. Nelson requested an instruction which read:

You are instructed that the defendant is allowed to use a motor vehicle of another person without permission if the use is for an emergency in the case of immediate and dire need.

You are further instructed that once the defendant has raised the issue of emergency or necessity, the state must prove the lack of emergency or necessity beyond a reasonable doubt.

Over Nelson’s objection, the court gave an instruction on the necessity defense which read as follows:

You are instructed that it is a defense to a crime such as joyriding or taking someone else’s motor vehicle without his permission that the person acted out of necessity in a case of immediate and dire need. However, such a defense exists only when natural forces create a situation wherein it becomes necessary for a person to violate the law in order to avoid a greater evil to himself or his property. The harm’ which is to be avoided must be the greater harm and it must be immediate and dire. Where a reasonable alternative other than violating the law is available in order to avoid the harm the defense of necessity is not applicable.4

*979Nelson argues that the jury instruction was erroneous because it allowed the jury to apply what he calls an “objective, after-the-fact” test of need and emergency, rather than a “subjective, reasonable man” test. By this we assume Nelson means that he was entitled to have explained to the jury that they must view the question of necessity from the standpoint of a reasonable person knowing all that the defendant did at the time he acted.

We affirm the conviction. We note at the outset that the instruction proposed by Nelson is similarly lacking of any explicit language allowing the jury to find necessity if there was a reasonable belief that an emergency existed as opposed to an actual emergency. Thus even if Nelson’s proposed instruction had been given verbatim the alleged error would not have been corrected. Beyond this, however, we find any error in the instruction given to have been harmless.

The defense of necessity may be raised if the defendant’s actions, although violative of the law, were necessary to prevent an even greater harm from occurring.

The rationale of the necessity defense is not that a person, when faced with the pressure of circumstances of nature, lacks the mental' element which the crime in question requires. Rather, it is this reason of public policy: the law ought to promote the achievement of higher values at the expense of lesser values, and sometimes the greater good for society will be accomplished by violating the literal language of the criminal law.

W. LaFave & A. Scott, Criminal Law § 50 at 382 (1972).

Commentators generally agree that there are three essential elements to the defense: 1) the act charged must have been done to prevent a significant evil; 2) there must have been no adequate alternative; 3) the harm caused must not have been disproportionate to the harm avoided. Arnolds & Garland, The Defense of Necessity in Criminal Law: The Right to Choose the Lesser Evil, 65 J. of Crim.L.P. & C.S. 289, 292 (1974); See W. LaFave & A. Scott, supra § 50 at 385-88.

The instruction given adequately describes these requirements for the jury. Nelson argues that he was entitled to wording which would explicitly allow the jury to find a necessity defense if a reasonable person at the time of acting would have believed that the necessary elements were present. Nelson is correct in stating that the necessity defense is available if a person acted in the reasonable belief that an emergency existed and there were no alternatives available even if that belief was mistaken.5 Moreover, the person’s actions *980should be weighed against the harm reasonably foreseeable at the time, rather than the harm that actually occurs.6

Assuming that the instruction given was not worded adequately to convey these concepts to the jury, we would find the error harmless, for Nelson failed to make out a case for the necessity defense. The “emergency” situation claimed by Nelson to justify his appropriation of the construction equipment was the alleged danger that his truck, stuck in the mud, might tip over, perhaps damaging the truck top. However by the time Nelson decided to use the equipment the truck had already been stuck for several hours. The dire nature of the emergency may be judged by the fact that some twelve hours later, having unsuccessfully attempted to remove the vehicle from the mud, one of Nelson’s companions fell asleep in the truck, which had still not tipped over.

Nor can it be said that Nelson had no lawful alternatives in his situation. The record shows that during the time Nelson was trying to free the vehicle people stopped on several different occasions and offered their services in the form of physical assistance; rides, or offers to telephone state troopers or a tow truck.

Finally, it cannot be said that the harm sought to be avoided in this case — potential damage to Nelson’s truck — was greater than the harm caused by Nelson’s illegal, actions. Even disregarding the actual damage to the equipment caused by Nelson’s use, the seriousness of the offenses committed by Nelson were disproportionate to the situation he faced. The legislature has made this clear by making reckless destruction of personal property a crime punishable by imprisonment for up to one year and a $5,000 fine,7 and joyriding punishable by imprisonment for up to one year and a $1,000 fine.8 The equipment taken by Nelson was marked with no trespassing signs. Nelson’s fears about damage to his truck roof were no justification for his appropriation of sophisticated and expensive equipment.

AFFIRMED.

*1020OPINION

FABE, Justice.

I. INTRODUCTION

In August 2006 Jennifer Greenwood fled from her home in North Pole in the middle of the night, believing that she was about to be attacked by her former boyfriend and that he was planning to burn down his parents' nearby home. After screaming for help and calling 911, Greenwood got into her van and drove away. Greenwood drove less than a mile to her ex-boyfriend's parents' home and honked to try to wake them. She then drove a few blocks to the nearest well-lighted area along the highway, where she stopped to wait for the troopers who were responding to her 911 call, flagging them down when they arrived.

Greenwood had been drinking, and she was arrested and charged with felony driving under the influence. After hearing evidence and testimony about these incidents, the trial court denied Greenwood a jury instruction on the necessity defense, concluding that Greenwood was justified only in driving as far as her ex-boyfriend's parents' home. A jury convicted Greenwood, and the court of appeals affirmed, reasoning that Greenwood had presented no evidence that the danger continued after she reached the parents' home and that she had the alternative of remaining in her van with the doors locked. Because we conclude that Greenwood presented some evidence of each of the elements of the necessity defense, we reverse and remand for a new trial with a necessity instruction.

II FACTS AND PROCEEDINGS

On August 10, 2006, Jennifer Greenwood was home alone in her camper in North Pole waiting for Jay Way to arrive. Greenwood wanted to speak with Way, whom she had dated that summer, about her missing puppy that she suspected he may have taken. Because Greenwood's camper did not have electricity, she started a bonfire outside and lit some candles both inside and outside of the camper. As it grew late, Greenwood assumed that Way was not coming, and she let the fire burn down and began preparing for bed.

But Way did arrive on his four wheeler, and he and Greenwood had a couple of glasses of wine. Greenwood testified that when she brought up the subject of the missing puppy, Way seemed "kind of [] mad," which made her feel vulnerable and afraid. Greenwood testified that she had been told that Way had been physically abusive with his previous girlfriend and had drug problems, and she decided that the best way to avoid conflict in the situation would be to agree to have sex with Way.

Afterwards, Greenwood went outside to check on the fire. While she was outside, she overheard Way "mumbling" inside the camper about how he was going to burn down both Greenwood's camper and his parents' home and how he would not go back to jail because "there won't be any witnesses." Greenwood then observed Way flinging the lit candles around her camper, so she began screaming for her neighbors to help her or call 911. When no one came to her aid, Greenwood ran into the woods barefoot with her other dog. She testified that she could hear Way thrashing around and throwing things, presumably in his search for her.

Greenwood's dog got away from her, ran towards Way, and began to bark. Way picked up a two-by-four board and swung it at the dog. While Way was distracted, Greenwood sneaked into the camper to grab her purse containing her cell phone and quietly headed back into the woods. Greenwood called her dog back to her and dialed 911 to request help. After she explained that Way was trying to burn down her house, the dispatch operator wanted her to stay on the line, but the dog got away again and started barking at Way, so Greenwood hung up. Way then hit Greenwood's dog with the two-by-four and began "to ride all around" on his four wheeler.

At that point, Greenwood ran to her van with her dog. She testified that she felt that she needed to get out of the situation and to drive to Way's parents' house to warn them of the danger because she did not have their telephone number. Greenwood decided to drive on the back road to reach Way's par*1021ents' house, less than a mile away, in order to avoid the fast traffic on the main road and to avoid crossing paths with Way. When Greenwood arrived at Way's parents' home, she saw that all of the lights were off, so she slowed down and honked her horn to try to rouse them. She did not stop because she was afraid of running into Way, who lived with his parents, and because there were no lights on at the house. Greenwood then drove a "couple of blocks" to the nearest well-lighted spot on the main road, Holmes Road. She parked to wait for the troopers who would be responding to her 911 call, and when she saw them, she flagged them down by honking her horn and opening her door.

When the troopers arrived sometime after 2:00 a.m., they found Greenwood distraught and crying on the side of the road. While interacting with Greenwood, the troopers smelled alcohol and observed that she was exhibiting signs of intoxication. Greenwood submitted to a portable breath test and was arrested for driving under the influence. A Datamaster test later showed Greenwood's blood aleohol concentration to be 0.184 percent.

Greenwood was charged with felony driving under the influence in violation of AS 28.35.030(n) on August 16, 2006. The case was assigned to Superior Court Judge Randy M. Olsen for trial. Before trial began, the State moved for a protective order that would prevent Greenwood from raising the affirmative defense of necessity. The trial court did not rule on this matter immediately, but instead elected to hear the evidence before making a decision. After the State presented its case, Greenwood made an offer of proof to the court on what her expected evidence of the defense would be. The court allowed her to present this evidence despite the State's argument that Greenwood had reasonable alternatives available to her.

After hearing Greenwood's testimony, the superior court stated that Greenwood had "at least created a jury question" as to whether or not Greenwood had an adequate alternative method of warning Way's parents of the evil she was seeking to prevent. The trial court ruled as a matter of law, however, that upon Greenwood's arrival at Way's parents' house, the necessity ended: "[Ojnce she got to the parents' house, she would have accomplished everything that she wanted to accomplish. It would've been warning the parents. It would've been finding a safe haven. It was a house that she knew. At that point, she was not justified in driving further." The court explained that "if there's a continuing offense, like drunk driving, the illegal conduct must be stopped as soon as the necessity ends," and it refused to instruct the jury on the necessity defense.

Greenwood immediately moved for reconsideration and a mistrial, arguing that "it would be extremely prejudicial" for her testimony to be stricken. The trial court denied both of the motions but did not strike Greenwood's testimony. Greenwood was convicted and sentenced to 24 months in prison with 20 months suspended.

Greenwood appealed her conviction to the court of appeals, arguing that she was entitled to a necessity instruction under the circumstances.1 The court of appeals affirmed the trial court's ruling, reasoning that Greenwood's failure to remain at Way's parents' house because she did not wish to encounter Way undermined her argument that it was necessary for her to drive to their house to warn them of Way's intentions, making an encounter with Way "seemingly ... inevitable." 2 The court of appeals further pointed out that Greenwood did not offer any evidence that Way ever arrived at his parents' house or that "she would have been in danger had she simply stayed in her car, with the doors locked, and continued honking her horn until she roused Way's parents." 3

Chief Judge Coats dissented from the memorandum - opinion, - maintaining - that Greenwood had "presented 'some evidence' to justify her decision to drive to the main road to contact the state troopers" because her testimony demonstrated that she was concerned about an encounter with Way and *1022that she wanted to ensure that the troopers were able to find both her and the Way residence.4 In the dissent's view, "a jury could reasonably find that Greenwood's decision to avoid a confrontation with Way was justifiable." 5 Moreover, the dissent noted that Greenwood had "asserted the basis for her defense before she was arrested." 6

We granted Greenwood's petition for hearing on the question of whether she was entitled to a necessity instruction at trial.

III. STANDARD OF REVIEW

"A defendant is entitled to a jury instruction on the necessity defense if [she] presents 'some evidence' in support of that defense."7 We review whether a defendant has presented some evidence of a proposed defense de novo after considering the entire record 8 and viewing the evidence in the light most favorable to the defendant.9

IV. DISCUSSION

"The common law defense of necessity is available to criminal defendants in Alaska except where preempted or excluded by the legislature."10 To receive the benefit of a necessity defense, the defendant must show the existence of three essential elements: "10 [the act charged must have been done to prevent a significant evil; 2) there must have been no adequate alternative; 3) the harm caused must not have been disproportionate to the harm avoided." 11 When the defendant is accused of a continuing offense, such as drunk driving, she "must also show some evidence that []4) she stopped violating the law as soon as the necessity ended." 12 In order to receive the benefit of this defense, the accused must have "reasonably believed at the time of acting that the first, second, and ... fourth elements were present." 13 The defendant's value judgment concerning the third element, whether the "reasonably foreseeable harm resulting from the violation would be less than the harm resulting from compliance with the law," is evaluated objectively using the facts as the defendant reasonably perceived them.14

If a defendant presents "some evidence" of each of these elements, the defendant is entitled to a jury instruction on the necessity defense.15 "'Some evidence' is evidence that, viewed in the light most favorable to the defendant, would allow a reasonable juror to find in the defendant's favor on each element of the defense."16 The "some evidence" burden is not a heavy one-as long as the defendant produces some evidence to support each element of the defense, "any weakness or implausibility in that evidence is irrelevant" 17 and "a matter for the jury, not for the court."18 As the court of appeals *1023noted, "a strong argument can be made that a trial judge should err on the side of giving instructions" on a proposed defense in order to prevent the jury from considering "its own understanding of what [the proposed] defense is in the absence of an instruction from the court."19

Greenwood argues that she presented some evidence of each element of the necessity defense and that she was therefore entitled to a jury instruction. The State counters that Greenwood failed to present evidence "from which a juror could conclude that her stated belief in the need to continue driving after reaching the Way home was reasonable." We consider de novo whether Greenwood has presented some evidence of each of the elements of the necessity defense."20

A. Greenwood Presented Some Evidence That She Drove Under The Influence To Prevent A Significant Evil.

Both the trial court and the court of appeals accepted Greenwood's contention that she needed to drive away from her camper on the night in question to prevent a significant evil.21 But both courts seemed to define the significant evil to be prevented narrowly: "impending arson" perpetrated against Way's parents.22 Greenwood argues a broader theory of the threat she was seeking to avoid, that "she was terrified for her safety and the safety of Way's parents."

Greenwood testified that she overheard Way say that he was planning on burning down his parents' home and would leave no witnesses and that she saw him take aggressive actions, such as throwing lit candles inside her camper and hitting her dog with a board. This testimony provides some evidence that Greenwood was seeking to prevent several evils: physical harm to herself, harm to Way's parents, and arson to her home and Way's parents' home. These harms are significant and consistent with the requirement that "the harm sought to be avoided by a defendant raising the necessity defense must have emanated either from a natural cause or from illegal human acts."23

As Chief Judge Coats pointed out in his dissent, "[ulnlike most cases where defendants claim, after the fact, that their violation of the law was justified by necessity, Greenwood asserted the basis for her defense before she was arrested." 24 Greenwood's fear apparently motivated her to call the police and then flag them down, despite the fact that it was obvious that she had broken the law by drinking and driving. This persuades us that she reasonably believed that her conduct was necessary at the time of acting. We conclude that Greenwood presented some evidence of the first element, that there were several significant harms that her actions were calculated to avoid.

B. Greenwood Presented Some Evidence That There Were No Adequate Alternatives And That The Necessity Continued Until She Stopped Driving.

We next consider whether Greenwood presented some evidence of both the second element-that there were no adequate alternatives to the unlawful action-and the fourth element-that the legal violation stopped as soon as the necessity ended. There is some inherent factual overlap between the second element and the fourth element because an alternative that becomes available at a given point during a continuing violation can serve to end the necessity. Because we look to the reasonableness of Greenwood's beliefs at the time she acted in evaluating whether she has presented some evidence of both the second and fourth ele*1024ments, we will consider these elements together."25

The trial court agreed with Greenwood that she provided some evidence of a necessity that required her to drive away from her camper and to Way's parents' house, and the court of appeals did not disturb this ruling.26 The court of appeals explained, "Greenwood presented no evidence to suggest that it was reasonable for her to believe (1) that this danger remained an immediate one [upon arriving at Way's parents' house] and (2) that she needed to continue driving to avert it." 27 The majority opinion reasoned that Greenwood's failure to stop at the Way residence because she did not want to encounter Way undercut her justification for driving there in the first place-warning Way's parents of his imminent arrival and intentions.28

The court of appeals also pointed to a potential alternative:

In addition, Greenwood offered no evidence that she would have been in danger had she simply stayed in her car, with the doors locked, and continued honking her horn until she roused Way's parents. Greenwood may have subjectively believed that it would not be safe for her to follow this course of action-but ... a defendant's subjective beliefs are not sufficient, standing alone, to establish this prong of the necessity defense.[29]

As previously stated, in deciding whether a defendant has produced some evidence that no adequate alternative existed and that the violation of the law ceased once the necessity ended, courts consider the defendant's reasonable beliefs at the time, even if those beliefs are mistaken, rather than objectively weighing all potential alternatives.30 The implausibility of a defendant's story, or any weakness in the evidence supporting that story, is not a relevant consideration.31 This standard is applied to both aspects of the second element-whether the defendant believed that alternatives existed and whether the defendant believed those alternatives were adequate-as well as to the fourth element. In applying the "some evidence" test in the related self-defense context, Alaska case law has emphasized that,

because reasonableness is a factual question closely allied with considerations involving the credibility of witnesses and the weight to be given to their testimony, trial courts must avoid basing decisions as to the necessity of self-defense instructions on an evaluation of the reasonableness of defendants' conduct. ... It is not the province of the judge to weigh the evidence and decide if a defendant's subjective belief was reasonable or unreasonable.[32]

It was therefore error for the court of appeals to conclude that Greenwood's subjective beliefs were not sufficient to satisfy the "some evidence" test for the second and fourth elements of the necessity defense.

This is not to say, however, that a court must always hold that the "some evidence" test has been met when a defendant asserts that her belief at the time was that there were no adequate alternatives. Instead, as the court of appeals explained in Seibold v. State, courts may refuse to instruct the jury on the necessity defense when the defendant had "clear legal alternatives to violating the law."33 When a defendant testifies to her beliefs at the time of acting, the question for the judge is whether a "clear legal alternative" existed such that the defendant is un*1025able as a matter of law to meet her burden of presenting some evidence that she reasonably believed that there were no adequate alternatives to her unlawful action.

Both this court and the court of appeals have upheld rulings where the existence of clear legal alternatives prevented a defendant from receiving a jury instruction on the necessity defense. For example, in Nelson v. State we held that the defendant, who had unlawfully used two Highway Department vehicles to free his truck that was stuck in a marshy area, had failed to make out the case for the necessity defense because several people had stopped and offered to help him, thus providing lawful alternatives.34 Similarly, in Cleveland v. Municipality of Anchorage we held that the defense of necessity was not available to defendants charged with trespassing at an abortion clinic in order to prevent abortions for several reasons, including that the defendants could have engaged in non-criminal forms of protest.35 The court of appeals likewise affirmed the trial court's refusal to instruct the jury on the necessity defense in Schnabel v. State when the defendant failed to pursue the judicial and administrative remedies available to resolve his claimed necessity.36 Finally, in Gerlach v. State the court of appeals concluded that a non-custodial mother who hid her daughter out of state for a year was not entitled to a necessity instruction based on her claim that the father was abusive because adequate remedies were available at law.37

We next turn to the question whether Greenwood fulfilled the requirement of some evidence for the second and fourth elements. The "some evidence" test does not require

that the defendant testify or even offer direct evidence in his own behalf. Some evidence establishing a dispute as to a factual issue may arise from weakness in the prosecution's evidence or from impeachment of its witness. Similarly, circumstantial evidence presented as part of the state's case-in-chief may give rise to some evidence of a disputed fact.[38]

In this case, we consider whether Greenwood provided some evidence that she reasonably believed at the time of driving that she had no adequate alternatives and that the necessity continued until she stopped her vehicle. These questions must be evaluated in light of our previous conclusion that the harms Greenwood was seeking to prevent included the threat to her own safety.

Our decision in McGee v. State provides guidance on when a court should conclude that a defendant has provided some evidence of a subjective belief that there were no adequate alternatives available.39 In McGeq, the defendant presented evidence that his mother's boyfriend threatened that he would run over the defendant, McGee.40 McGee maintained that he feared that the boyfriend would make good on this threat because of an earlier physical altercation, so McGee claimed to have smashed the windows of the boyfriend's pickup truck to make sure that the boyfriend could not see him to run him over.41 We held that, although there were likely many other available options, McGee's testimony raised a question of fact concerning whether he reasonably failed to recognize those other options because of his agitated mental state.42 Consistent with McGee, we also consider that the threat to Greenwood's safety was fresh and imminent, and we take into account the emotions that a person in her position could have experienced.

*1026Greenwood's evidence, including her testimony that she first screamed for help and called 911 before deciding to drive away to escape a dangerous situation, demonstrates that she exhausted the most obvious of her alternatives before deciding to take the ile-gal action. She also offered testimony that she was unwilling to stop at the Way residence and risk a confrontation with her attacker because Way was on a four wheeler and she was unsure of his whereabouts when she approached the Way residence in her van. As Greenwood argued, she had reason to suspect that Way "was likely to return" to his parents' house because "Way also live[d] at that house." Greenwood's other actions, such as stopping of her own accord in a well-lighted area, where she waited for police until she flagged them down, are consistent with her understanding of the necessity-her need to escape from Way and to warn his parents of the potential harm by waking them.

The court of appeals concluded that Greenwood failed to present some evidence of the fourth element because Greenwood did not offer any evidence that it would have been dangerous for her to sit in her locked van outside of Way's parents' house while honk ing to wake the parents.43 We disagree. To meet the "some evidence" test for the fourth element, Greenwood is not required to present evidence that every possible alternative was unavailable to her; instead she need only provide some evidence that she reasonably believed that the necessity continued until the point that she stopped violating the law, even if that belief was mistaken.44 Furthermore, even if she was required to present evidence that she reasonably believed that this alternative was not available to her and that she believed the necessity continued because she could not stop and wait, Greenwood's testimony that Way had access to a two-by-four that he had previously employed as a weapon against her dog provided a foundation for a reasonable belief that she was not safe waiting in a dark car, even with the doors locked.

We therefore conclude that Greenwood's testimony constituted some evidence sufficient to enable a reasonable juror to decide that Greenwood reasonably believed that she had no adequate alternatives to breaking the law by driving under the influence-even if that belief was mistaken-and that she stopped driving onee she believed the necessity had ended.

C. Greenwood Presented Some Evidence That The Reasonably Foreseeable Harm Resulting From Her Unlawful Action Would Be Less Than The Harm Resulting From Her Compliance With The Law.

The third element of proportionality requires that "[aln objective determination ... be made as to whether the defendant's value judgment was correct, given the facts as [she] reasonably perceived them." 45 As discussed previously, the trial court and the court of appeals assumed that the only harm that Greenwood was seeking to avoid was "possible arson or a threat of arson," but we have concluded that the potential harm to Greenwood herself must also be considered. The harm that Greenwood identifies, including risk to her personal safety because of Way's threats and physical aggression, are significant.46 Further, her testimony about the rumors that she had heard about Way's drug use and violent history are relevant because the "third element requires an objective comparison of the relative seriousness of the harms caused and avoided when viewed *1027in light of the facts perceived by the defendant." 47

Our analysis and balancing process must also account for the serious risk that drunk driving poses to the public,48 particularly because we consider the harm reasonably foreseeable from a defendant's actions, not the harm that actually occurred.49 Greenwood had already exhausted available options such as screaming for help and calling the police, and she testified that she took concrete steps to mitigate the risk of driving under the influence by driving on a back road and reaching speeds of only 35 miles per hour. Although driving any distance under the influence poses a significant risk, Greenwood testified that she continued driving only "a couple of blocks" after reaching Way's parents' home until she reached a well-lighted home on the route that she assumed that the troopers would take in responding to her 911 call-a total drive of less than one mile from beginning to end.

Considering that the trial court and the court of appeals agreed that Greenwood was justified in driving the distance between her camper and the Way residence, the question presented is whether Greenwood's decision to continue driving those last few blocks was disproportionate to the harm she was seeking to prevent-potential physical harm to herself resulting from an altercation with Way. As Chief Judge Coats pointed out in his dissent, "[plolice agencies often warn the public to seek police help rather than to directly intervene in potentially dangerous situations." 50 The rationale behind the necessity defense is one of public policy: "the law ought to promote the achievement of higher values at the expense of lesser values, and sometimes the greater good for society will be accomplished by violating the literal language of the criminal law." 51

Because the threshold for the "some evidence" test only requires "more than a scintilla" of evidence with any doubt resolved in Greenwood's favor,52 we conclude that Greenwood has offered some evidence of the third element. Viewing the totality of the situation from Greenwood's perspective and considering her testimony regarding her emotional distress, we cannot conclude that there was not some evidence presented that the serious risk that she posed by driving under the influence was disproportionate to the serious physical injury, significant property damage, and other harms she reasonably feared at the time.

v. CONCLUSION

Because we conclude that Greenwood has met the "some evidence" test with respect to all four elements required for an instruction on the necessity defense, we REVERSE her conviction and REMAND for a new trial at which an instruction on Greenwood's necessity defense be given.

Justice Souter

delivered the opinion of the Court.

The case presents two questions: whether due process prohibits Arizona’s use of an insanity test stated solely in terms of the capacity to tell whether an act charged as a crime was right or wrong; and whether Arizona violates due process in restricting consideration of defense evidence of mental illness and incapacity to its bearing on a claim of insanity, thus eliminating its significance directly on the issue of the mental element of the crime charged (known in legal shorthand as the mens rea, or guilty mind). We hold that there is no violation of due process in either instance.

*743I

In the early hours of June 21, 2000, Officer Jeffrey Moritz of the Flagstaff Police responded in uniform to complaints that a pickup truck with loud music blaring was circling a residential block. When he located the truck, the officer turned on the emergency lights and siren of his marked patrol car, which prompted petitioner Eric Clark, the truck’s driver (then 17), to pull over. Officer Moritz got out of the patrol car and told Clark to stay where he was. Less than a minute later, Clark shot the officer, who died soon after but not before calling the police dispatcher for help. Clark ran away on foot but was arrested later that day with gunpowder residue on his hands; the gun that killed the officer was found nearby, stuffed into a knit cap.

Clark was charged with first-degree murder under Ariz. Rev. Stat. Ann. § 13-1105(A)(3) (West Supp. 2005) for intentionally or knowingly killing a law enforcement officer in the line of duty.1 In March 2001, Clark was found incompetent to stand trial and was committed to a state hospital for treatment, but two years later the same trial court found his competence restored and ordered him to be tried. Clark waived his right to a jury, and the case was heard by the court.

At trial, Clark did not contest the shooting and death, but relied on his undisputed paranoid schizophrenia at the time of the incident in denying that he had the specific intent to shoot a law enforcement officer or knowledge that he was doing so, as required by the statute. Accordingly, the prosecutor offered circumstantial evidence that Clark knew Officer Moritz was a law enforcement officer. The evidence showed that the officer was in uniform at the time, that he caught *744up with Clark in a marked police car with emergency lights and siren going, and that Clark acknowledged the symbols of police authority and stopped. The testimony for the prosecution indicated that Clark had intentionally lured an officer to the scene to kill him, having told some people a few weeks before the incident that he wanted to shoot police officers. At the close of the State’s evidence, the trial court denied Clark’s motion for judgment of acquittal for failure to prove intent to kill a law enforcement officer or knowledge that Officer Moritz was a law enforcement officer.

In presenting the defense case, Clark claimed mental illness, which he sought to introduce for two purposes. First, he raised the affirmative defense of insanity, putting the burden on himself to prove by clear and convincing evidence, § 13-502(C) (West 2001), that “at the time of the commission of the criminal act [he] was afflicted with a mental disease or defect of such severity that [he] did not know the criminal act was wrong,” §13-502(A).2 Second, he aimed to rebut the prosecution’s evidence of the requisite mens rea, that he had acted intentionally or knowingly to kill a law enforcement officer. See, e. g., Record in No. CR 2000-538 (Ariz. Super. Ct.), Doc. 374 (hereinafter Record).

*745The trial court ruled that Clark could not rely on evidence bearing on insanity to dispute the mens rea. The court cited State v. Mott, 187 Ariz. 536, 931 P. 2d 1046, cert. denied, 520 U. S. 1234 (1997), which “refused to allow psychiatric testimony to negate specific intent,” 187 Ariz., at 541, 931 P. 2d, at 1051, and held that “Arizona does not allow evidence of a defendant’s mental disorder short of insanity ... to negate the mens rea element of a crime,” ibid3

As to his insanity, then, Clark presented testimony from classmates, school officials, and his family describing his increasingly bizarre behavior over the year before the shooting. Witnesses testified, for example, that paranoid delusions led Clark to rig a fishing line with beads and wind chimes at home to alert him to intrusion by invaders, and to keep a bird in his automobile to warn of airborne poison. There was lay and expert testimony that Clark thought Flagstaff was populated with “aliens” (some impersonating government agents), the “aliens” were trying to kill him, and bullets were the only way to stop them. A psychiatrist testified that Clark was suffering from paranoid schizophrenia with delusions about “aliens” when he killed Officer Moritz, and he concluded that Clark was incapable of luring the officer or understanding right from wrong and that he was thus insane at the time of the killing. In rebuttal, a psychiatrist for the State gave his opinion that Clark’s paranoid schizophrenia did not keep him from appreciating the wrongfulness of his conduct, as shown by his actions before and after the shooting (such as circling the residential block with music blaring as if to lure the police to intervene, evading the police after the shooting, and hiding the gun).

At the close of the defense case consisting of this evidence bearing on mental illness, the trial court denied Clark’s re*746newed motion for a directed verdict grounded on failure of the prosecution to show that Clark knew the victim was a police officer.4 The judge then issued a special verdict of first-degree murder, expressly finding that Clark shot and caused the death of Officer Moritz beyond a reasonable doubt and that Clark had not shown that he was insane at the time. The judge noted that though Clark was indisputably afflicted with paranoid schizophrenia at the time of the shooting, the mental illness “did not . . . distort his perception of reality so severely that he did not know his actions were wrong.” App. 334. For this conclusion, the judge expressly relied on “the facts of the crime, the evaluations of the experts, [Clark’s] actions and behavior both before and after the shooting, and the observations of those that knew [Clark].” Id., at 333. The sentence was life imprisonment without the possibility of release for 25 years.

Clark moved to vacate the judgment and sentence, arguing, among other things, that Arizona’s insanity test and its Mott rule each violate due process. As to the insanity standard, Clark claimed (as he had argued earlier) that the Arizona Legislature had impermissibly narrowed its standard in 1993 when it eliminated the first part of the two-part insanity test announced in M’Naghten’s Case, 10 Cl. & Fin. 200, 8 Eng. Rep. 718 (1843). The court denied the motion.

The Court of Appeals of Arizona affirmed Clark’s conviction, treating the conclusion on sanity as supported by enough evidence to withstand review for abuse of discretion, and holding the State’s insanity scheme consistent with due process. App. 336. As to the latter, the Court of Appeals reasoned that there is no constitutional requirement to recognize an insanity defense at all, the bounds of which are left to the State’s discretion. Beyond that, the appellate court followed Mott, reading it as barring the trial court’s consid*747eration of evidence of Clark’s mental illness and capacity directly on the element of mens rea. The Supreme Court of Arizona denied further review.

We granted certiorari to decide whether due process prohibits Arizona from thus narrowing its insanity test or from excluding evidence of mental illness and incapacity due to mental illness to rebut evidence of the requisite criminal intent. 546 U. S. 1060 (2005). We now affirm.

II

Clark first says that Arizona’s definition of insanity, being only a fragment of the Victorian standard from which it derives, violates due process. The landmark English rule in M’Naghten’s Case, supra, states that

“the jurors ought to be told . . . that to establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was laboring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or, if he did know it, that he did not know he was doing what was wrong.” Id., at 210, 8 Eng. Rep., at 722.

The first part asks about cognitive capacity: whether a mental defect leaves a defendant unable to understand what he is doing. The second part presents an ostensibly alternative basis for recognizing a defense of insanity understood as a lack of moral capacity: whether a mental disease or defect leaves a defendant unable to understand that his action is wrong.

When the Arizona Legislature first codified an insanity rule, it adopted the full M’Naghten statement (subject to modifications in details that do not matter here):

“A person is not responsible for criminal conduct if at the time of such conduct the person was suffering from such a mental disease or defect as not to know the na*748ture and quality of the act or, if such person did know, that such person did not know that what he was doing was wrong.” Ariz. Rev. Stat. Ann. §13-502 (West 1978).5

In 1993, the legislature dropped the cognitive incapacity part, leaving only moral incapacity as the nub of the stated definition. See 1993 Ariz. Sess. Laws ch. 256, §§ 2—3.6 Under current Arizona law, a defendant will not be adjudged insane unless he demonstrates that “at the time of the commission of the criminal act [he] was afflicted with a mental disease or defect of such severity that [he] did not know the criminal act was wrong,” Ariz. Rev. Stat. Ann. § 13-502(A) (West 2001).

A

Clark challenges the 1993 amendment excising the express reference to the cognitive incapacity element. He insists that the side-by-side M’Naghten test represents the minimum that a government must provide in recognizing an alternative to criminal responsibility on grounds of mental illness or defect, and he argues that elimination of the M’Naghten reference to nature and quality “ ‘offends [a] principle of justice so rooted in the traditions and conscience of our people as to be ranked as fundamental,’” Patterson v. *749New York, 432 U. S. 197, 202 (1977) (quoting Speiser v. Randall, 357 U. S. 513, 523 (1958)); see also Leland v. Oregon, 343 U. S. 790, 798 (1952).

The claim entails no light burden, see Montana v. Egelhoff, 518 U. S. 37, 43 (1996) (plurality opinion), and Clark does not carry it. History shows no deference to M’Naghten that could elevate its formula to the level of fundamental principle, so as to limit the traditional recognition of a State’s capacity to define crimes and defenses, see Patterson, supra, at 210; see also Foucha v. Louisiana, 504 U. S. 71, 96 (1992) (Kennedy, J., dissenting).

Even a cursory examination of the traditional Anglo-American approaches to insanity reveals significant differences among them, with four traditional strains variously combined to yield a diversity of American standards. The main variants are the cognitive incapacity, the moral incapacity, the volitional incapacity, and the product-of-mental-illness tests.7 The first two emanate from the alternatives stated in the M’Naghten rule. The volitional incapacity or irresistible-impulse test, which surfaced over two centuries ago (first in England,8 then in this country9), asks whether a person was so lacking in volition due to a mental defect or illness that he could not have controlled his actions. And the product-of-mental-illness test was used as early as 1870,10 and simply asks whether a person’s action was a prod*750uct of a mental disease or defect.11 Seventeen States and the Federal Government have adopted a recognizable version of the M’Naghten test with both its cognitive incapacity and moral incapacity components.12 One State has adopted *751only M’Naghten’s cognitive incapacity test,13 and 10 (including Arizona) have adopted the moral incapacity test alone.14 Fourteen jurisdictions, inspired by the Model Penal Code,15 have in place an amalgam of the volitional incapacity test and some variant of the moral incapacity test, satisfaction of either (generally by showing a defendant’s substantial lack of capacity) being enough to excuse.16 Three States combine a full M’Naghten test with a volitional incapacity formula.17 And New Hampshire alone stands by the product-of-mental-illness test.18 The alternatives are multiplied further by variations in the prescribed insanity verdict: a significant number of these jurisdictions supplement the traditional “not guilty by reason of insanity” verdict with an *752alternative of “guilty but mentally ill.”19 Finally, four States have no affirmative insanity defense,20 though one provides for a “guilty and mentally ill” verdict.21 These four, like a number of others that recognize an affirmative insanity defense, allow consideration of evidence of mental illness directly on the element of mens rea defining the offense.22

With this varied background, it is clear that no particular formulation has evolved into a baseline for due process, and that the insanity rule, like the conceptualization of criminal offenses, is substantially open to state choice. Indeed, the legitimacy of such choice is the more obvious when one considers the interplay of legal concepts of mental illness or deficiency required for an insanity defense, with the medical concepts of mental abnormality that influence the expert opinion testimony by psychologists and psychiatrists commonly introduced to support or contest insanity claims. For medical definitions devised to justify treatment, like legal ones devised to excuse from conventional criminal responsibility, are subject to flux and disagreement. See infra, at *753774-775; cf. Leland, 343 U. S., at 800-801 (no due process violation for adopting the M’Naghten standard rather than the irresistible-impulse test because scientific knowledge does not require otherwise and choice of test is a matter of policy). There being such fodder for reasonable debate about what the cognate legal and medical tests should be, due process imposes no single canonical formulation of legal insanity.

B

Nor does Arizona’s abbreviation of the M’Naghten statement raise a proper claim that some constitutional minimum has been shortchanged. Clark’s argument of course assumes that Arizona’s former statement of the M’Naghten rule, with its express alternative of cognitive incapacity, was constitutionally adequate (as we agree). That being so, the abbreviated rule is no less so, for cognitive incapacity is relevant under that statement, just as it was under the more extended formulation, and evidence going to cognitive incapacity has the same significance under the short form as it had under the long.

Though Clark is correct that the application of the moral incapacity test (telling right from wrong) does not necessarily require evaluation of a defendant’s cognitive capacity to appreciate the nature and quality of the acts charged against him, see Brief for Petitioner 46-47, his argument fails to recognize that cognitive incapacity is itself enough to demonstrate moral incapacity. Cognitive incapacity, in other words, is a sufficient condition for establishing a defense of insanity, albeit not a necessary one. As a defendant can therefore make out moral incapacity by demonstrating cognitive incapacity, evidence bearing on whether the defendant knew the nature and quality of his actions is both relevant and admissible. In practical terms, if a defendant did not know what he was doing when he acted, he could not have known that he was performing the wrongful act charged as *754a crime.23 Indeed, when the two-part rule was still in effect, the Supreme Court of Arizona held that a jury instruction on insanity containing the moral incapacity part but not a full recitation of the cognitive incapacity part was fine, as the cognitive incapacity part might be “‘treated as adding nothing to the requirement that the accused know his act was wrong.’” State v. Chavez, 143 Ariz. 238, 239, 693 P. 2d 893, 894 (1984) (quoting A. Goldstein, The Insanity Defense 50 (1967)).

The Court of Appeals of Arizona acknowledged as much in this case, too, see App. 350 (“It is difficult to imagine that a defendant who did not appreciate the ‘nature and quality’ of the act he committed would reasonably be able to perceive that the act was ‘wrong’ ”), and thus aligned itself with the long-accepted understanding that the cognitively incapacitated are a subset of the morally incapacitated within the meaning of the standard M’Naghten rule, see, e. g., Goldstein, supra, at 51 (“In those situations where the accused does not know the nature and quality of his act, in the broad sense, he will not know that it was wrong, no matter what construction ‘wrong’ is given”); 1 W. LaFave, Substantive Criminal Law § 7.2(b)(3), p. 536 (2d ed. 2003) (“Many courts feel that knowledge of ‘the nature and quality of the act’ is the mere equivalent of the ability to know that the act was wrong” (citing cases)); id., § 7.2(b)(4), at 537 (“If the defendant does not know the nature and quality of his act, then quite obviously he does not know that his act is ‘wrong,’ and this is true without regard to the interpretation given to the word *755‘wrong’”); cf. 1 R. Gerber, Criminal Law of Arizona 502-7, n. 1 (2d ed. 1993).24

Clark, indeed, adopted this very analysis himself in the trial court: “[I]f [Clark] did not know he was shooting at a police officer, or believed he had to shoot or be shot, even though his belief was not based in reality, this would establish that he did not know what he was doing was wrong.” Record, Doc. 374, at 1. The trial court apparently agreed, for the judge admitted Clark’s evidence of cognitive incapacity for consideration under the State’s moral incapacity formulation. And Clark can point to no evidence bearing on *756insanity that was excluded. His psychiatric expert and a number of lay witnesses testified to his delusions, and this evidence tended to support a description of Clark as lacking the capacity to understand that the police officer was a human being. There is no doubt that the trial judge considered the evidence as going to an issue of cognitive capacity, for in finding insanity not proven he said that Clark’s mental illness “did not . . . distort his perception of reality so severely that he did not know his actions were wrong,” App. 334.

We are satisfied that neither in theory nor in practice did Arizona’s 1993 abridgment of the insanity formulation deprive Clark of due process.

Ill

Clark’s second claim of a due process violation challenges the rule adopted by the Supreme Court of Arizona in State v. Mott, 187 Ariz. 536, 931 P. 2d 1046, cert. denied, 520 U. S. 1234 (1997). This case ruled on the admissibility of testimony from a psychologist offered to show that the defendant suffered from battered women’s syndrome and therefore lacked the capacity to form the mens rea of the crime charged against her. The opinion variously referred to the testimony in issue as “psychological testimony,” 187 Ariz., at 541, 931 P. 2d, at 1051, and “expert testimony,” ibid., and implicitly equated it with “expert psychiatric evidence,” id., at 540, 931 P. 2d, at 1050 (internal quotation marks omitted), and “psychiatric testimony,” id., at 541, 931 P. 2d, at 1051.25 The state court held that testimony of a professional psychologist or psychiatrist about a defendant’s mental incapacity owing to mental disease or defect was admissible, and could be considered, only for its bearing on an insanity defense; such evidence could not be considered on the element *757of mens rea, that is, what the State must show about a defendant’s mental state (such as intent or understanding) when he performed the act charged against him. See id., at 541, 544, 931 P. 2d, at 1051, 1054.26

A

Understanding Clark’s claim requires attention to the categories of evidence with a potential bearing on mens rea. First, there is “observation evidence” in the everyday sense, testimony from those who observed what Clark did and heard what he said; this category would also include testimony that an expert witness might give about Clark’s tendency to think in a certain way and his behavioral characteristics. This evidence may support a professional diagnosis of mental disease and in any event is the kind of evidence that can be relevant to show what in fact was on Clark’s mind when he fired the gun. Observation evidence in the record covers Clark’s behavior at home and with friends, his expressions of belief around the time of the killing that “aliens” were inhabiting the bodies of local people (including government agents),27 his driving around the neighborhood before the police arrived, and so on. Contrary to the dissent’s characterization, see post, at 782 (opinion of Kennedy, J.), obser*758vation evidence can be presented by either lay or expert witnesses.

Second, there is “mental-disease evidence” in the form of opinion testimony that Clark suffered from a mental disease with features described by the witness. As was true here, this evidence characteristically but not always28 comes from professional psychologists or psychiatrists who testify as expert witnesses and base their opinions in part on examination of a defendant, usually conducted after the events in question. The thrust of this evidence was that, based on factual reports, professional observations, and tests, Clark was psychotic at the time in question, with a condition that fell within the category of schizophrenia.

Third, there is evidence we will refer to as “capacity evidence” about a defendant’s capacity for cognition and moral judgment (and ultimately also his capacity to form mens rea). This, too, is opinion evidence. Here, as it usually does,29 this testimony came from the same experts and concentrated on those specific details of the mental condition that make the difference between sanity and insanity under the Arizona definition.30 In their respective testimony on *759these details the experts disagreed: the defense expert gave his opinion that the symptoms or effects of the disease in Clark’s case included inability to appreciate the nature of his action and to tell that it was wrong, whereas the State’s psychiatrist was of the view that Clark was a schizophrenic who was still sufficiently able to appreciate the reality of shooting the officer and to know that it was wrong to do that.31

A caveat about these categories is in order. They attempt to identify different kinds of testimony offered in this case in terms of explicit and implicit distinctions made in Mott. What we can say about these categories goes to their cores, however, not their margins. Exact limits have thus not been worked out in any Arizona law that has come to our attention, and in this case, neither the courts in their rulings nor counsel in objections invoked or required precision in applying the Mott rule’s evidentiary treatment, as we explain below. Necessarily, then, our own decision can address only core issues, leaving for other cases any due process claims that may be raised about the treatment of evidence whose categorization is subject to dispute.

*760B

It is clear that Mott itself imposed no restriction on considering evidence of the first sort, the observation evidence. We read the Mott restriction to apply, rather, to evidence addressing the two issues in testimony that characteristically comes only from psychologists or psychiatrists qualified to give opinions as exp'ert witnesses: mental-disease evidence (whether at the time of the crime a defendant suffered from a mental disease or defect, such as schizophrenia) and capacity evidence (whether the disease or defect left him incapable of performing or experiencing a mental process defined as necessary for sanity such as appreciating the nature and quality of his act and knowing that it was wrong).

Mott was careful to distinguish this kind of opinion evidence from observation evidence generally and even from observation evidence that an expert witness might offer, such as descriptions of a defendant’s tendency to think in a certain way or his behavioral characteristics; the Arizona court made it clear that this sort of testimony was perfectly admissible to rebut the prosecution’s evidence of mens rea, 187 Ariz., at 544, 931 P. 2d, at 1054. Thus, only opinion testimony going to mental defect or disease, and its effect on the cognitive or moral capacities on which sanity depends under the Arizona rule, is restricted.

In this case, the trial court seems to have applied the Mott restriction to all evidence offered by Clark for the purpose of showing what he called his inability to form the required mens rea, see, e.g., Record, Doc. 406, at 7-10 (that is, an intent to kill a police officer on duty, or an understanding that he was engaging in the act of killing such an officer, see Ariz. Rev. Stat. Ann. § 13-1105(A)(3) (West Supp. 2005)). Thus, the trial court’s restriction may have covered not only mental-disease and capacity evidence as just defined, but also observation evidence offered by lay (and expert) witnesses who described Clark’s unusual behavior. Clark’s objection to the application of the Mott rule does not, however, turn *761on the distinction between lay and expert witnesses or the kinds of testimony they were competent to present.32

C

There is some, albeit limited, disagreement between the dissent and ourselves about the scope of the claim of error properly before us. To start with matters of agreement, all Members of the Court agree that Clark’s general attack on the Mott rule covers its application in confining consideration of capacity evidence to the insanity defense.

In practical terms, our agreement on issues presented extends to a second point. Justice Kennedy understands that Clark raised an objection to confining mental-disease evidence to the insanity issue. As he sees it, Clark in effect claimed that in dealing with the issue of mens rea the trial judge should have considered expert testimony on what may characteristically go through the mind of a schizophrenic, when the judge considered what in fact was in Clark’s mind at the time of the shooting. See post, at 783 (dissenting opinion) (“[T]he opinion that Clark had paranoid schizophrenia—an opinion shared by experts for both the prosecution and defense—bears on efforts to determine, as a factual matter, whether he knew he was killing a police officer”). He thus understands that defense counsel claimed a right to rebut the State’s mens rea demonstration with testimony about how schizophrenics may hallucinate voices and other sounds, about their characteristic failure to distinguish the content of their imagination from what most people perceive as exterior reality, and so on. It is important to be clear that this supposed objection was not about dealing with tes*762timony based on observation of Clark showing that he had auditory hallucinations when he was driving around, or failed in fact to appreciate objective reality when he shot; this objection went to use of testimony about schizophrenics, not about Clark in particular. While we might dispute how clearly Clark raised this objection, we have no doubt that the objection falls within a general challenge to the Mott rule; we understand that Mott is meant to confine to the insanity defense any consideration of characteristic behavior associated with mental disease, see 187 Ariz., at 544, 931 P. 2d, at 1054 (contrasting State v. Christensen, 129 Ariz. 32, 628 P. 2d 580 (1981), and State v. Gonzales, 140 Ariz. 349, 681 P. 2d 1368 (1984)). We will therefore assume for argument that Clark raised this claim, as we consider the due process challenge to the Mott rule.

The point on which we disagree with the dissent, however, is this: did Clark apprise the Arizona courts that he believed the trial judge had erroneously limited the consideration of observation evidence, whether from lay witnesses like Clark’s mother or (possibly) the expert witnesses who observed him? This sort of evidence was not covered by the Mott restriction, and confining it to the insanity issue would have been an erroneous application of Mott as a matter of Arizona law. For the following reasons we think no such objection was made in a way the Arizona courts could have understood it, and that no such issue is before us now. We think the only issue properly before us is the challenge to Mott on due process grounds, comprising objections to limits on the use of mental-disease and capacity evidence.

It is clear that the trial judge intended to apply Mott:

“[R]ecognizing that much of the evidence that [the defense is] going to be submitting, in fact all of it, as far as I know ... that has to do with the insanity could also arguably be made along the lines of the Mott issues as to form and intent and his capacity for the intent. I’m going to let you go ahead and get all that stuff in because *763it goes to the insanity issue and because we’re not in front of a jury. At the end, I’ll let you make an offer of proof as to the intent, the Mott issues, but I still think the supreme court decision is the law of the land in this state.” App. 9.

At no point did the trial judge specify any particular evidence that he refused to consider on the mens rea issue. Nor did defense counsel specify any observation or other particular evidence that he claimed was admissible but wrongly excluded on the issue of mens rea, so as to produce a clearer ruling on what evidence was being restricted on the authority of Mott and what was not. He made no “offer of proof” in the trial court;33 and although his brief in the Arizona Court of Appeals stated at one point that it was not inconsistent with Mott to consider nonexpert evidence indicating mental illness on the issue of mens rea, and argued that the trial judge had failed to do so, Appellant’s Opening Brief in No. 1CA-CR-03-0851 etc., pp. 48-49 (hereinafter Appellant’s Opening Brief), he was no more specific than that, see, e. g., id., at 52 (“The Court’s ruling in Mott and the trial court’s refusal to consider whether as a result of suffering from paranoid schizophrenia [Clark] could not formulate the mens rea necessary for first degree murder violated his right to due process”). Similarly, we read the Arizona Court of Appeals to have done nothing more than rely on Mott to reject the claim that due process forbids restricting evidence bearing on “[ajbility to [florm [m]ens [r]ea,” App. 351 (em*764phasis in original), (i. e., mental-disease and capacity evidence) to the insanity determination. See id., at 351-353.

This failure in the state courts to raise any clear claim about observation evidence, see Appellant’s Opening Brief 46-52, is reflected in the material addressed to us, see Brief for Petitioner 13-32. In this Court both the question presented and the following statement of his position were couched in similarly worded general terms:

“I. ERIC WAS DENIED DUE PROCESS WHEN THE TRIAL COURT REFUSED TO CONSIDER EVIDENCE OF HIS SEVERE MENTAL ILLNESS IN DETERMINING FACTUALLY WHETHER THE PROSECUTION PROVED THE MENTAL ELEMENTS OF THE CRIME CHARGED.” Id., at 13.

But as his counsel made certain beyond doubt in his reply brief,

“Eric’s Point I is and always has been an attack on the rule of State v. Mott, which both courts below held applicable and binding. Mott announced a categorical ‘rejection of the use of psychological testimony to challenge the mens rea element of a crime,’ and upheld this rule against federal due process challenge.” Reply Brief for Petitioner 2 (citations omitted).

This explanation is supported by other statements in Clark’s briefs in both the State Court of Appeals and this Court, replete with the consistently maintained claim that it was error to limit evidence of mental illness and incapacity to its bearing on the insanity defense, excluding it from consideration on the element of mens rea. See, e. g., Appellant’s Opening Brief 46,47,51; Brief for Petitioner 11,13,16,20-23.

In sum, the trial court’s ruling, with its uncertain edges, may have restricted observation evidence admissible on mens rea to the insanity defense alone, but we cannot be *765sure.34 But because a due process challenge to such a restriction of observation evidence was, by our measure, neither pressed nor passed upon in the Arizona Court of Appeals, we do not consider it. See, e. g., Kentucky v. Stincer, 482 U. S. 730, 747, n. 22 (1987); Illinois v. Gates, 462 U. S. 213, 217-224 (1983). What we do know, and now consider, is Clark’s claim that Mott denied due process because it “preclude [dj Eric from contending that. . .factual inferences” of the “mental states which were necessary elements of the crime charged” “should not be drawn because the behavior was explainable, instead, as a manifestation of his chronic paranoid schizophrenia.” Brief for Petitioner 13 (emphasis in original). We consider the claim, as Clark otherwise puts it, that “Arizona’s prohibition of ‘diminished capacity’ evidence by criminal defendants violates” due process, ibid.

D

Clark’s argument that the Mott rule violates the Fourteenth Amendment guarantee of due process turns on the application of the presumption of innocence in criminal cases, the presumption of sanity, and the principle that a criminal defendant is entitled to present relevant and favorable evidence on an element of the offense charged against him.

*7661

The first presumption is that a defendant is innocent unless and until the government proves beyond a reasonable doubt each element of the offense charged, see Patterson, 432 U. S., at 210-211; In re Winship, 397 U. S. 358, 361-364 (1970), including the mental element or mens rea. Before the last century, the mens rea required to be proven for particular offenses was often described in general terms like “malice,” see, e. g., In re Eckart, 166 U. S. 481 (1897); 4 W. Blackstone, Commentaries *21 (“[A]n unwarrantable act without a vicious will is no crime at all”), but the modern tendency has been toward more specific descriptions, as shown in the Arizona statute defining the murder charged against Clark: the State had to prove that in acting to kill the victim, Clark intended to kill a law enforcement officer on duty or knew that the victim was such an officer on duty. See generally Gardner, The Mens Rea Enigma: Observations on the Role of Motive in the Criminal Law Past and Present, 1993 Utah L. Rev. 635. As applied to mens rea (and every other element), the force of the presumption of innocence is measured by the force of the showing needed to overcome it, which is proof beyond a reasonable doubt that a defendant’s state of mind was in fact what the charge states. See Winship, supra, at 361-363.

2

The presumption of sanity is equally universal in some variety or other, being (at least) a presumption that a defendant has the capacity to form the mens rea necessary for a verdict of guilt and the consequent criminal responsibility. See Leland, 343 U. S., at 799; Davis v. United States, 160 U. S. 469, 486-487 (1895); M’Naghten’s Case, 10 Cl. & Fin., at 210, 8 Eng. Rep., at 722; see generally 1 LaFave, Substantive Criminal Law § 8.3(a), at 598-599, and n. 1. This presumption dispenses with a requirement on the government’s part *767to include as an element of every criminal charge an allegation that the defendant had such a capacity.35 The force of this presumption, like the presumption of innocence, is measured by the quantum of evidence necessary to overcome it; unlike the presumption of innocence, however, the force of the presumption of sanity varies across the many state and federal jurisdictions, and prior law has recognized considerable leeway on the part of the legislative branch in defining the presumption’s strength through the kind of evidence and degree of persuasiveness necessary to overcome it, see Fisher v. United States, 328 U. S. 463, 466-476 (1946).36

There are two points where the sanity or capacity presumption may be placed in issue. First, a State may allow a defendant to introduce (and a factfinder to consider) evidence of mental disease or incapacity for the bearing it can have on the government’s burden to show mens rea. See, e. g., State v. Perez, 882 A. 2d 574, 584 (R. I. 2005).37 In such States the evidence showing incapacity to form the guilty state of mind, for example, qualifies the probative force of other evidence, which considered alone indicates that the defendant actually formed the guilty state of mind. If it is shown that a defendant with mental disease thinks all blond people are robots, he could not have intended to kill a person when he shot a man with blond hair, even though he seemed *768to act like a man shooting another man.38 In jurisdictions that allow mental-disease and capacity evidence to be considered on par with any other relevant evidence when deciding whether the prosecution has proven mens rea beyond a reasonable doubt, the evidence of mental disease or incapacity need only support what the factfinder regards as a reasonable doubt about the capacity to form (or the actual formation of) the mens rea, in order to require acquittal of the charge. Thus, in these States the strength of the presumption of sanity is no greater than the strength of the evidence of abnormal mental state that the factfinder thinks is enough to raise a reasonable doubt.

The second point where the force of the presumption of sanity may be tested is in the consideration of a defense of insanity raised by a defendant. Insanity rules like M’Naghten and the variants discussed in Part II, supra, are attempts to define, or at least to indicate, the kinds of mental differences that overcome the presumption of sanity or capacity and therefore excuse a defendant from customary criminal responsibility, see Jones v. United States, 463 U. S. 354, 373, n. 4 (1983) (Brennan, J., dissenting); D. Hermann, The Insanity Defense: Philosophical, Historical and Legal Perspectives 4 (1983) (“A central significance of the insanity defense . . . *769is the separation of nonblameworthy from blameworthy offenders”), even if the prosecution has otherwise overcome the presumption of innocence by convincing the factfinder of all the elements charged beyond a reasonable doubt. The burden that must be carried by a defendant who raises the insanity issue, again, defines the strength of the sanity presumption. A State may provide, for example, that whenever the defendant raises a claim of insanity by some quantum of credible evidence, the presumption disappears and the government must prove sanity to a specified degree of certainty (whether beyond reasonable doubt or something less). See, e.g., Commonwealth v. Keita, 429 Mass. 843, 846, 712 N. E. 2d 65, 68 (1999). Or a jurisdiction may place the burden of persuasion on a defendant to prove insanity as the applicable law defines it, whether by a preponderance of the evidence or to some more convincing degree, see Ariz. Rev. Stat. Ann. § 13-502(C) (West 2001); Leland, 343 U. S., at 798. In any case, the defendant’s burden defines the presumption of sanity, whether that burden be to burst a bubble or to show something more.

3

The third principle implicated by Clark’s argument is a defendant’s right as a matter of simple due process to present evidence favorable to himself on an element that must be proven to convict him.39 As already noted, evidence tending to show that a defendant suffers from mental disease and lacks capacity to form mens rea is relevant to rebut evidence that he did in fact form the required mens rea at the time in question; this is the reason that Clark claims a right to require the factfinder in this case to consider testimony *770about his mental illness and his incapacity directly, when weighing the persuasiveness of other evidence tending to show mens rea, which the prosecution has the burden to prove.

As Clark recognizes, however, the right to introduce relevant evidence can be curtailed if there is a good reason for doing that. “While the Constitution ... prohibits the exclusion of defense evidence under rules that serve no legitimate purpose or that are disproportionate to the ends that they are asserted to promote, well-established rules of evidence permit trial judges to exclude evidence if its probative value is outweighed by certain other factors such as unfair prejudice, confusion of the issues, or potential to mislead the jury.” Holmes v. South Carolina, 547 U. S. 319, 326 (2006); see Crane v. Kentucky, 476 U. S. 683, 689-690 (1986) (permitting exclusion of evidence that “poses an undue risk of ‘harassment, prejudice, [or] confusion of the issues’ ” (quoting Delaware v. Van Arsdall, 475 U. S. 673, 679 (1986))); see also Egelhoff, 518 U. S. 37; Chambers v. Mississippi, 410 U. S. 284, 302 (1973). And if evidence may be kept out entirely, its consideration may be subject to limitation, which Arizona claims the power to impose here. State law says that evidence of mental disease and incapacity may be introduced and considered, and if sufficiently forceful to satisfy the defendant’s burden of proof under the insanity rule it will displace the presumption of sanity and excuse from criminal responsibility. But mental-disease and capacity evidence may be considered only for its bearing on the insanity defense, and it will avail a defendant only if it is persuasive enough to satisfy the defendant’s burden as defined by the terms of that defense. The mental-disease and capacity evidence is thus being channeled or restricted to one issue and given effect only if the defendant carries the burden to convince the factfinder of insanity; the evidence is not being excluded entirely, and the question is whether reasons for requiring it to be channeled and restricted are good enough to *771satisfy the standard of fundamental fairness that due process requires. We think they are.

E

1

The first reason supporting the Mott rule is Arizona’s authority to define its presumption of sanity (or capacity or responsibility) by choosing an insanity definition, as discussed in Part II, supra, and by placing the burden of persuasion on defendants who claim incapacity as an excuse from customary criminal responsibility. No one, certainly not Clark here, denies that a State may place a burden of persuasion on a defendant claiming insanity, see Leland, supra, at 797-799 (permitting a State, consistent with due process, to require the defendant to bear this burden). And Clark presses no objection to Arizona’s decision to require persuasion to a clear and convincing degree before the presumption of sanity and normal responsibility is overcome. See Brief for Petitioner 18, n. 25.

But if a State is to have this authority in practice as well as in theory, it must be able to deny a defendant the opportunity to displace the presumption of sanity more easily when addressing a different issue in the course of the criminal trial. Yet, as we have explained, just such an opportunity would be available if expert testimony of mental disease and incapacity could be considered for whatever a factfinder might think it was worth on the issue of mens rea.40 As we mentioned, the presumption of sanity would then be only as strong as the evidence a factfinder would accept as enough to raise a reasonable doubt about mens rea for the crime charged; once reasonable doubt was found, acquittal would *772be required, and the standards established for the defense of insanity would go by the boards.

Now, a State is of course free to accept such a possibility in its law. After all, it is free to define the insanity defense by treating the presumption of sanity as a bursting bubble, whose disappearance shifts the burden to the prosecution to prove sanity whenever a defendant presents any credible evidence of mental disease or incapacity. In States with this kind of insanity rule, the legislature may well be willing to allow such evidence to be considered on the mens rea element for whatever the factfinder thinks it is worth. What counts for due process, however, is simply that a State that wishes to avoid a second avenue for exploring capacity, less stringent for a defendant, has a good reason for confining the consideration of evidence of mental disease and incapacity to the insanity defense.

It is obvious that Arizona’s Mott rule reflects such a choice. The State Supreme Court pointed out that the State had declined to adopt a defense of diminished capacity (allowing a jury to decide when to excuse a defendant because of greater than normal difficulty in conforming to the law).41 The court reasoned that the State’s choice would be undercut if evidence of incapacity could be considered for *773whatever a jury might think sufficient to raise a reasonable doubt about mens rea, even if it did not show insanity. 187 Ariz., at 541, 931 P. 2d, at 1051. In other words, if a jury were free to decide how much evidence of mental disease and incapacity was enough to counter evidence of mens rea to the point of creating a reasonable doubt, that would in functional terms be analogous to allowing jurors to decide upon some degree of diminished capacity to obey the law, a degree set by them, that would prevail as a stand-alone defense.42

2

A State’s insistence on preserving its chosen standard of legal insanity cannot be the sole reason for a rule like Mott, however, for it fails to answer an objection the dissent makes in this case. See post, at 789-797 (opinion of Kennedy, J.). An insanity rule gives a defendant already found guilty the opportunity to excuse his conduct by showing he was insane when he acted, that is, that he did not have the mental capacity for conventional guilt and criminal responsibility. But, as the dissent argues, if the same evidence that affirmatively shows he was not guilty by reason of insanity (or “guilty except insane” under Arizona law, Ariz. Rev. Stat. Ann. § 13-502(A) (West 2001)) also shows it was at least doubtful that he could form mens rea, then he should not be found guilty in the first place; it thus violates due process when the State *774impedes him from using mental-disease and capacity evidence directly to rebut the prosecution’s evidence that he did form mens rea.

Are there, then, characteristics of mental-disease and capacity evidence giving rise to risks that may reasonably be hedged by channeling the consideration of such evidence to the insanity issue on which, in States like Arizona, a defendant has the burden of persuasion? We think there are: in the controversial character of some categories of mental disease, in the potential of mental-disease evidence to mislead, and in the danger of according greater certainty to capacity evidence than experts claim for it.

To begin with, the diagnosis may mask vigorous debate within the profession about the very contours of the mental disease itself. See, e. g., American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders xxxiii (4th ed. text rev. 2000) (hereinafter DSM-IV-TR) (“DSM-IV reflects a consensus about the classification and diagnosis of mental disorders derived at the time of its initial publication. New knowledge generated by research or clinical experience will undoubtedly lead to an increased understanding of the disorders included in DSM-IV, to the identification of new disorders, and to the removal of some disorders in future classifications. The text and criteria sets included in DSM-IV will require reconsideration in light of evolving new information”); P. Caplan, They Say You’re Crazy: How the World’s Most Powerful Psychiatrists Decide Who’s Normal (1995) (criticism by former consultant to the DSM against some of the DSM’s categories). And Members of this Court have previously recognized that the end of such debate is not imminent. See Jones, 463 U. S., at 365, n. 13 (“ ‘The only certain thing that can be said about the present state of knowledge and therapy regarding mental disease is that science has not reached finality of judgment’ ” (quoting Greenwood v. United States, 350 U. S. 366, 375 (1956))); Powell v. Texas, 392 U. S. 514, 537 (1968) (plurality opinion) (“It *775is simply not yet the time to write into the Constitution formulas cast in terms whose meaning, let alone relevance, is not yet clear ... to doctors”). Though we certainly do not “condem[n mental-disease evidence] wholesale,” Brief for American Psychiatric Association et al. as Amici Curiae 15, the consequence of this professional ferment is a general caution in treating psychological classifications as predicates for excusing otherwise criminal conduct.

Next, there is the potential of mental-disease evidence to mislead jurors (when they are the factfinders) through the power of this kind of evidence to suggest that a defendant suffering from a recognized mental disease lacks cognitive, moral, volitional, or other capacity, when that may not be a sound conclusion at all. Even when a category of mental disease is broadly accepted and the assignment of a defendant’s behavior to that category is uneontroversial, the classification may suggest something very significant about a defendant’s capacity, when in fact the classification tells us little or nothing about the ability of the defendant to form mens rea or to exercise the cognitive, moral, or volitional capacities that define legal sanity.43 See DSM-IV-TR xxxii-xxxiii (“When the DSM-IV categories, criteria, and textual descriptions are employed for forensic purposes, there are significant risks that diagnostic information will be misused or misunderstood. These dangers arise because of the imperfect fit between the questions of ultimate concern to the law and the information contained in a clinical diagnosis. In most situations, the clinical diagnosis of a DSM-IV mental disorder is not sufficient to establish the existence for legal *776purposes of. . . ‘mental diseas[e]’ or ‘mental defect.’ In determining whether an individual meets a specified legal standard (e. g., for ... criminal responsibility ...), additional information is usually required beyond that contained in the DSM-IV diagnosis”). The limits of the utility of a professional disease diagnosis are evident in the dispute between the two testifying experts in this case; they agree that Clark was schizophrenic, but they come to opposite conclusions on whether the mental disease in his particular case left him bereft of cognitive or moral capacity. Evidence of mental disease, then, can easily mislead; it is very easy to slide from evidence that an individual with a professionally recognized mental disease is very different, into doubting that he has the capacity to form mens rea, whereas that doubt may not be justified. And of course, in the cases mentioned before, in which the categorization is doubtful or the category of mental disease is itself subject to controversy, the risks are even greater that opinions about mental disease may confuse a jury into thinking the opinions show more than they do. Because allowing mental-disease evidence on mens rea can thus easily mislead, it is not unreasonable to address that tendency by confining consideration of this kind of evidence to insanity, on which a defendant may be assigned the burden of persuasion.

There are, finally, particular risks inherent in the opinions of the experts who supplement the mental-disease classifications with opinions on incapacity: on whether the mental disease rendered a particular defendant incapable of the cognition necessary for moral judgment or mens rea or otherwise incapable of understanding the wrongfulness of the conduct charged. Unlike observational evidence bearing on mens rea, capacity evidence consists of judgment, and judgment fraught with multiple perils: a defendant’s state of mind at the crucial moment can be elusive no matter how conscientious the enquiry, and the law’s categories that set the terms of the capacity judgment are not the categories of psychology *777that govern the expert’s professional thinking. Although such capacity judgments may be given in the utmost good faith, their potentially tenuous character is indicated by the candor of the defense expert in this very case. Contrary to the State’s expert, he testified that Clark lacked the capacity to appreciate the circumstances realistically and to understand the wrongfulness of what he was doing, App. 48-49, but he said that “no one knows exactly what was on [his] mind” at the time of the shooting, id., at 48. And even when an expert is confident that his understanding of the mind is reliable, judgment addressing the basic categories of capacity requires a leap from the concepts of psychology, which are devised for thinking about treatment, to the concepts of legal sanity, which are devised for thinking about criminal responsibility. See Insanity Defense Work Group, American Psychiatric Association Statement on the Insanity Defense, 140 Am. J. Psychiatry 681,686 (1983), reprinted in 2 The Role of Mental Illness in Criminal Trials 117,122 (J. Moriarty ed. 2001) (“The American Psychiatric Association is not opposed to legislatures restricting psychiatric testimony about the... ultimate legal issues concerning the insanity defense. . . . When . . . ‘ultimate issue’ questions are formulated by the law and put to the expert witness who must then say ‘yea’ or ‘nay,’ then the expert witness is required to make a leap in logic. He no longer addresses himself to medical concepts but instead must infer or intuit what is in fact unspeakable, namely, the probable relationship between medical concepts and legal or moral constructs such as free will. These impermissible leaps in logic made by expert witnesses confuse the jury. . . . This state of affairs does considerable injustice to psychiatry and, we believe, possibly to criminal defendants. These psychiatric disagreements . . . cause less than fully understanding juries or the public to conclude that psychiatrists cannot agree. In fact, in many criminal insanity trials both prosecution and defense psychiatrists do agree about the nature and even the extent of mental disorder ex*778hibited by the defendant at the time of the act” (emphasis in original; footnote omitted)); DSM-IV-TR xxxii-xxxiii; R Giannelli & E. Imwinkelried, Scientific Evidence §9-3(B), p. 286 (1986) (“[N]o matter how the test for insanity is phrased, a psychiatrist or psychologist is no more qualified than any other person to give an opinion about whether a particular defendant’s mental condition satisfies the legal test for insanity”); cf. R. Slovenko, Psychiatry and Criminal Culpability 55 (1995) (“The scope of the DSM is wide-ranging and includes ‘conduct disorders’ but ‘evil’ is not mentioned”). In sum, these empirical and conceptual problems add up to a real risk that an expert’s judgment in giving capacity evidence will come with an apparent authority that psychologists and psychiatrists do not claim to have. We think that this risk, like the difficulty in assessing the significance of mental-disease evidence, supports the State’s decision to channel such expert testimony to consideration on the insanity defense, on which the party seeking the benefit of this evidence has the burden of persuasion.

It bears repeating that not every State will find it worthwhile to make the judgment Arizona has made, and the choices the States do make about dealing with the risks posed by mental-disease and capacity evidence will reflect their varying assessments about the presumption of. sanity as expressed in choices of insanity rules.44 The point here simply is that Arizona has sensible reasons to assign the risks as it has done by channeling the evidence.45

*779F

Arizona’s rule serves to preserve the State’s chosen standard for recognizing insanity as a defense and to avoid confusion and misunderstanding on the part of jurors.46 For these reasons, there is no violation of due process under Chambers and its progeny, and no cause to claim that channeling evidence on mental disease and capacity offends any “‘principle of justice so rooted in the traditions and conscience of our people as to be ranked as fundamental,’ ” Patterson, 432 U. S., at 202 (quoting Speiser, 357 U. S., at 523).

* * *

The judgment of the Court of Appeals of Arizona is, accordingly, affirmed.

It is so ordered.

Justice Breyer,

concurring in part and dissenting in part.

As I understand the Court’s opinion, it distinguishes among three categories of evidence related to insanity: (1) fact-related evidence as to the defendant’s specific state of mind at the time of the crime, e. g., evidence that shows he *780thought the policeman was not a human being; (2) expert opinion evidence that the defendant suffered from a mental disease that would have affected his capacity to form an intent to kill a policeman, e. g., that he suffers from a disease of a kind where powerful voices command the sufferer to kill; and (3) expert opinion evidence that the defendant was legally insane, e. g., evidence that he did not know right from wrong. Ante, at 757-759.

I agree with the Court’s basic categorization. I also agree that the Constitution permits a State to provide for consideration of the second and third types of evidence solely in conjunction with the insanity defense. A State might reasonably fear that, without such a rule, the types of evidence as to intent would become confused in the jury’s mind, indeed that in some cases the insanity question would displace the intent question as the parties litigate both simultaneously.

Nonetheless, I believe the distinction among these kinds of evidence will be unclear in some cases. And though I accept the majority’s reading of the record, I remain concerned as to whether the lower courts, in setting forth and applying State v. Mott, 187 Ariz. 536, 931 P. 2d 1046, cert. denied, 520 U. S. 1234 (1997), focused with sufficient directness and precision upon the distinction.

Consequently, I would remand this case so that Arizona’s courts can determine whether Arizona law, as set forth in Mott and other cases, is consistent with the distinction the Court draws and whether the trial court so applied Arizona law here. I would also reserve the question (as I believe the Court has done) as to the burden of persuasion in a case where the defendant produces sufficient evidence of the second kind as to raise a reasonable doubt suggesting that he suffered from a mental illness so severe as to prevent him from forming any relevant intent at all.

For this reason, I dissent only from Parts III-B and III-C of the Court’s opinion and the ultimate disposition of this case, and I join the remainder.

*781Justice Kennedy, with whom Justice Stevens and Justice Ginsburg join, dissenting.

In my submission the Court is incorrect in holding that Arizona may convict petitioner Eric Clark of first-degree murder for the intentional or knowing killing of a police officer when Clark was not permitted to introduce critical and reliable evidence showing he did not have that intent or knowledge. The Court is wrong, too, when it concludes the issue cannot be reached because of an error by Clark’s counsel. Its reasons and conclusions lead me to file this respectful dissent.

Since I would reverse the judgment of the Arizona Court of Appeals on this ground, and the Arizona courts might well alter their interpretation of the State’s criminal responsibility statute were my rationale to prevail, it is unnecessary for me to address the argument that Arizona’s definition of insanity violates due process.

I

Clark claims that the trial court erred in refusing to consider evidence of his chronic paranoid schizophrenia in deciding whether he possessed the knowledge or intent required for first-degree murder. Seizing upon a theory invented here by the Court itself, the Court narrows Clark’s claim so he cannot raise the point everyone else thought was involved in the case. The Court says the only issue before us is whether there is a right to introduce mental-disease evidence or capacity evidence, not a right to introduce observation evidence. See ante, at 756-765. This restructured evidentiary universe, with no convincing authority to support it, is unworkable on its own terms. Even were that not so, however, the Court’s tripartite structure is something not addressed by the state trial court, the state appellate court, counsel on either side in those proceedings, or the briefs the parties filed with us. The Court refuses to consider the key part of Clark’s claim because his counsel did *782not predict the Court’s own invention. It is unrealistic, and most unfair, to hold that Clark’s counsel erred in failing to anticipate so novel an approach. If the Court is to insist on its approach, at a minimum the case should be remanded to determine whether Clark is bound by his counsel’s purported waiver.

The Court’s error, of course, has significance beyond this case. It adopts an evidentiary framework that, in my view, will be unworkable in many cases. The Court classifies Clark’s behavior and expressed beliefs as observation evidence but insists that its description by experts must be mental-disease evidence or capacity evidence. See ante, at 757-759. These categories break down quickly when it is understood how the testimony would apply to the question of intent and knowledge at issue here. The most common type of schizophrenia, and the one Clark suffered from, is paranoid schizophrenia. See P. Berner et al., Diagnostic Criteria for Functional Psychoses 37 (2d ed. 1992). The existence of this functional psychosis is beyond dispute, but that does not mean the lay witness understands it or that a disputed issue of fact concerning its effect in a particular instance is not something for the expert to address. Common symptoms of the condition are delusions accompanied by hallucinations, often of the auditory type, which can cause disturbances of perception. Ibid. Clark’s expert testified that people with schizophrenia often play radios loudly to drown out the voices in their heads. See App. 32. Clark’s attorney argued to the trial court that this, rather than a desire to lure a policeman to the scene, explained Clark’s behavior just before the killing. Id., at 294-295. The observation that schizophrenics play radios loudly is a fact regarding behavior, but it is only a relevant fact if Clark has schizophrenia.

Even if this evidence were, to use the Court’s term, mental-disease evidence, because it relies on an expert opinion, what would happen if the expert simply were to testify, without mentioning schizophrenia, that people with Clark’s *783symptoms often play the radio loudly? This seems to be factual evidence, as the term is defined by the Court, yet it differs from mental-disease evidence only in forcing the witness to pretend that no one has yet come up with a way to classify the set of symptoms being described. More generally, the opinion that Clark had paranoid schizophrenia—an opinion shared by experts for both the prosecution and defense—bears on efforts to determine, as a factual matter, whether he knew he was killing a police officer. The psychiatrist’s explanation of Clark’s condition was essential to understanding how he processes sensory data and therefore to deciding what information was in his mind at the time of the shooting. Simply put, knowledge relies on cognition, and cognition can be affected by schizophrenia. See American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders 299 (4th ed. text rev. 2000) (“The characteristic symptoms of Schizophrenia involve a range of cognitive and emotional dysfunctions that include perception”); ibid. (Symptoms include delusions, which are “erroneous beliefs that usually involve a misinterpretation of perceptions or experiences”). The mental-disease evidence at trial was also intertwined with the observation evidence because it lent needed credibility. Clark’s parents and friends testified Clark thought the people in his town were aliens trying to kill him. These claims might not be believable without a psychiatrist confirming the story based on his experience with people who have exhibited similar behaviors. It makes little sense to divorce the observation evidence from the explanation that makes it comprehensible.

Assuming the Court’s tripartite structure were feasible, the Court is incorrect when it narrows Clark’s claim to exclude any concern about observation evidence. In deciding Clark’s counsel failed to raise this issue, the Court relies on a series of perceived ambiguities regarding how the claim fits within the Court’s own categories. See ante, at 761-765. The Court cites no precedent for construing these ambiguities against the claimant and no prudential reason for ignor*784ing the breadth of Clark’s claim. It is particularly surprising that the Court does so to the detriment of a criminal defendant asserting the fundamental challenge that the trier of fact refused to consider critical evidence showing he is innocent of the crime charged.

The alleged ambiguities are, in any event, illusory. The evidence at trial addressed more than the question of general incapacity or opinions regarding mental illness; it went further, as it included so-called observation evidence relevant to Clark’s mental state at the moment he shot the officer. There was testimony, for example, that Clark thought the people in his town, particularly government officials, were not human beings but aliens who were trying to kill him. See App. 119-121, 131-132, 192-197, 249-256; Tr. of Bench Trial in No. CR 2000-538, pp. 110-112,131-132,136, 226-228 (Aug. 20, 2003); id., at 24-25, 59-60 (Aug. 21, 2003). The Court recognizes the existence of this essential observation evidence. See ante, at 757-759.

The Court holds, nonetheless, that “we cannot be sure” whether the trial court failed to consider this evidence. Ante, at 764-765. It is true the trial court ruling was not perfectly clear. Its language does strongly suggest, though, that it did not consider any of this testimony in deciding whether Clark had the knowledge or intent required for first-degree murder. After recognizing that “much of the evidence that [the defense is] going to be submitting, in fact all of it, as far as I know ... that has to do with the insanity could also arguably be made ... as to form and intent and his capacity for the intent,” the court concluded “we will be focusing, as far as I’m concerned, strictly on the insanity defense.” App. 9. In announcing its verdict, the trial court did not mention any of the mental-illness evidence, observation or otherwise, in deciding Clark’s guilt. Id., at 331-335. The most reasonable assumption, then, would seem to be that the trial court did not consider it, and the Court does not hold otherwise. See ante, at 760-761.

*785Clark’s objection to this refusal by the trier of fact to consider the evidence as it bore on his key defense was made at all stages of the proceeding. In his post-trial motion to vacate the judgment, Clark argued that “prohibiting consideration of any evidence reflecting upon a mentally ill criminal defendant’s ability to form the necessary mens rea violates due process.” Record, Doc. 406, p. 8. Clark pressed the same argument in the Arizona Court of Appeals. See Appellant’s Opening Brief in No. 1CA-CR-03-0851 etc., pp. 46-52 (hereinafter Appellant’s Opening Brief). He also noted that the trial judge had erred in refusing to consider nonexpert testimony—presumably what the Court would call observation evidence—on Clark’s mental illness. Id,., at 47-48 (“The trial court therefore violated [Clark’s] right to present a defense because [the] court refused to consider any evidence, including the multiple testimonials of lay witnesses ... in deciding whether he could form the requisite mens rea”). The appeals court decided the issue on the merits, holding that the trial court was correct not to consider the evidence of mental illness in determining whether Clark had the mens rea for first-degree murder. See App. 351-353. It offered no distinction at all between observation or mental-disease evidence.

Notwithstanding the appeals court’s decision, the Court states that the issue was not clearly presented to the state courts. See ante, at 762-765. According to the Court, Clark only raised an objection based on State v. Mott, 187 Ariz. 536, 931 P. 2d 1046 (1997), cert. denied, 520 U. S. 1234 (1997), see ante, at 762-765, and Mott’s holding was limited to the exclusion of mental-disease and capacity evidence, see ante, at 760. The Court is incorrect, and on both counts.

First, Clark’s claim goes well beyond an objection to Mott. In fact, he specifically attempted to distinguish Mott by noting that the trial court in this case refused to consider all evidence of mental illness. See Record, Doc. 406, at 8; see *786also Appellant’s Opening Brief 48. The Court notices these arguments but criticizes Clark’s counsel for not being specific about the observation evidence he wanted the trial court to consider. See ante, at 763. There was no reason, though, for Clark’s counsel to believe additional specificity was required, since there was no evident distinction in Arizona law between observation evidence and mental-disease testimony.

Second, Mott’s holding was not restricted to mental-disease evidence. The Arizona Supreme Court did not refer to any distinction between observation and mental-disease evidence, or lay and expert testimony. Its holding was stated in broad terms: “Arizona does not allow evidence of a defendant’s mental disorder short of insanity either as an affirmative defense or to negate the mens rea element of a crime.” 187 Ariz., at 541, 931 P. 2d, at 1051; see id., at 540, 931 P. 2d, at 1050 (“The legislature’s decision . . . evidences its rejection of the use of psychological testimony to challenge the mens rea element of a crime”). The Court attempts to divine a fact/opinion distinction in Mott based on Mott’s distinguishing a case, State v. Christensen, 129 Ariz. 32, 628 P. 2d 580 (1981), where evidence about behavioral tendencies was deemed admissible. See ante, at 760. Christensen, though, also addressed an expert opinion; the difference was that the evidence there concerned a “character trait of acting reflexively in response to stress,” not a mental illness. Mott, supra, at 544, 931 P. 2d, at 1054. Since the Court recognizes the Arizona Court of Appeals relied on Mott, the expansive rule of exclusion in Mott— without any suggestion of a limitation depending on the kind of evidence—should suffice for us to reach the so-called observation-evidence issue. Even if, as the Court contends, see ante, at 760, Mott is limited to expert testimony, the Court’s categories still do not properly interpret Mott, because the Court’s own definition of observation evidence includes some expert testimony, see ante, at 757-758.

It makes no difference that in the appeals court Clark referred to the issue as inability to form knowledge or intent. *787See Appellant’s Opening Brief 46-52. He did not insist on some vague, general incapacity. He stated, instead, that he “suffered from a major mental illness and was psychotic at the time of the offense.” Id., at 48. Even if Clark’s arguments were insufficient to apprise the state court of the argument, “[o]ur traditional rule is that ‘[ojnce a federal claim is properly presented, a party can make any argument in support of that claim; parties are not limited to the precise arguments they made below.’” Lebron v. National Railroad Passenger Corporation, 513 U. S. 374, 379 (1995) (quoting Yee v. Escondido, 503 U. S. 519, 534 (1992)). The claim is clear. Though it seems to be obscure to this Court, it was understood by the Arizona Court of Appeals, which stated: “Clark argues that the trial court erred in refusing to consider evidence of his mental disease or defect in determining whether he had the requisite mens rea to commit first-degree murder.” App. 351. When the question is what the state court held, it is not instructive for this Court to recast the words the state court used.

The razor-thin distinction the Court draws between evidence being used to show incapacity and evidence being used to show lack of mens rea directly does not identify two different claims. Clark’s single claim, however characterized, involves the use of the same mental-illness evidence to decide whether he had the requisite knowledge or intent. The various ways in which the evidence is relevant in disproving mens rea hardly qualify as separate claims. The new arguments allowed in Lebrón and Yee, by comparison, were far more disconnected from the initial bases for the alleged violations. See Lebron, supra, at 378, 379 (for purposes of showing state action, petitioner could argue that Amtrak was a Government entity even though he argued below only that it was a private entity with close connections to Government entities, because the claim was simply “that Amtrak did not accord him the rights it was obliged to provide by the First Amendment”); Yee, supra, at 534, 535 (petitioners *788could argue that an ordinance constituted a regulatory taking, even though they arguably asserted in the Court of Appeals only a physical taking, because the claim was simply “that the ordinance effects an unconstitutional taking”). If we give this latitude to litigants in civil cases, surely we must do so here. Furthermore, to the extent any ambiguity remains on whether the claim was raised, the proper course is to remand. See Bradshaw v. Richey, 546 U. S. 74, 80 (2005) (per curiam). Unless the state court clearly decides an issue on state-law grounds, which the Court does not contend occurred here, there is no bar to our review of the federal question. See Harris v. Reed, 489 U. S. 255, 261-262 (1989).

Before this Court Clark framed the issue in broad terms that encompass the question whether the evidence of his mental illness should have been considered to show he did not at the time of the offense have the knowledge or intent to shoot a police officer. See Brief for Petitioner i (“Questions Presented for Review (1) Whether Arizona’s blanket exclusion of evidence and refusal to consider mental disease or defect to rebut the state’s evidence on the element of mens rea violated Petitioner’s right to due process under the United States Constitution, Fourteenth Amendment?”), 22 (“Here, the trial court held that under the Mott rule it was obliged to find as a fact that [Clark] knew he was shooting a police officer to death—a necessary factual element of the only form of first degree murder charged against [Clark]— while simultaneously refusing to consider [Clark’s] evidence that an acute episode of his chronic paranoid schizophrenic illness prevented him from actually having that knowledge” (emphasis deleted)), 31-32 (the Arizona courts erred in holding Clark “could be punished as though he had this knowledge and' intent although he may not in fact have had either”); Reply Brief for Petitioner 3 (challenging the trial judge’s refusal “to give any consideration to the mental-illness evidence in making his factual findings as to whether *789[Clark] did or did not act with the state of mind required for a first-degree murder conviction”). An entire section of Clark’s opening brief argues that the evidence of mental illness should have been considered to rebut the prosecution’s inference of knowledge or intent from the factual circumstances of the crime. See Brief for Petitioner 13-21. This line of argument concerns facts of behavior and amounts to more than a claim of general incapacity.

Clark seeks resolution of issues that can be complex and somewhat overlapping. In the end, however, we must decide whether he had the right to introduce evidence showing he lacked the intent or knowledge the statute itself sets forth in describing a basic element of the crime. Clark has preserved this issue at all stages, including in this Court.

II

Clark was charged with first-degree murder for the shooting of Officer Jeffrey Moritz. “A person commits first-degree murder if,” as relevant here, “[intending or knowing that the person’s conduct will cause death to a law enforcement officer, the person causes the death of a law enforcement officer who is in the line of duty.” Ariz. Rev. Stat. Ann. § 13-1105(A)(3) (West Supp. 2005). Clark challenges the trial court’s refusal to consider any evidence of mental illness, from lay or expert testimony, in determining whether he acted with the knowledge or intent element of the crime. See App. 9; see also Mott, 187 Ariz., at 541, 931 P. 2d, at 1051.

States have substantial latitude under the Constitution to define rules for the exclusion of evidence and to apply those rules to criminal defendants. See United States v. Scheffer, 523 U. S. 303, 308 (1998). This authority, however, has constitutional limits. “Whether rooted directly in the Due Process Clause of the Fourteenth Amendment or in the Compulsory Process or Confrontation Clauses of the Sixth Amendment, the Constitution guarantees criminal defendants “a meaningful opportunity to present a complete de*790fense.”’” Holmes v. South Carolina, 547 U. S. 319, 324 (2006) (quoting Crane v. Kentucky, 476 U. S. 683, 690 (1986), in turn quoting California v. Trombetta, 467 U. S. 479, 485 (1984)). “This right is abridged by evidence rules that ‘infring[e] upon a weighty interest of the accused’ and are ‘“arbitrary” or “disproportionate to the purposes they are designed to serve.” ’ ” Holmes, supra, at 324 (quoting Scheffer, supra, at 308, in turn citing and quoting Rock v. Arkansas, 483 U. S. 44, 58, 56 (1987)).

The central theory of Clark’s defense was that his schizophrenia made him delusional. He lived in a universe where the delusions were so dominant, the theory was, that he had no intent to shoot a police officer or knowledge he was doing so. It is one thing to say he acted with intent or knowledge to pull the trigger. It is quite another to say he pulled the trigger to kill someone he knew to be a human being and a police officer. If the trier of fact were to find Clark’s evidence sufficient to discount the case made by the State, which has the burden to prove knowledge or intent as an element of the offense, Clark would not be guilty of first-degree murder under Arizona law.

The Court attempts to diminish Clark’s interest by treating mental-illness evidence as concerning only “judgment,” rather than fact. Ante, at 776-777. This view appears to derive from the Court’s characterization of Clark’s claim as raising only general incapacity. See ibid. This is wrong for the reasons already discussed. It fails to recognize, moreover, the meaning of the offense element in question here. The mens rea element of intent or knowledge may, at some level, comprise certain moral choices, but it rests in the first instance on a factual determination. That is the fact Clark sought to put in issue. Either Clark knew he was killing a police officer or he did not.

The issue is not, as the Court insists, whether Clark’s mental illness acts as an “excuse from customary criminal responsibility,” ante, at 771, but whether his mental illness, as *791a factual matter, made him unaware that he was shooting a police officer. If it did, Clark needs no excuse, as then he did not commit the crime as Arizona defines it. For the elements of first-degree murder, where the question is knowledge of particular facts—that one is killing a police officer— the determination depends not on moral responsibility but on empirical fact. Clark’s evidence of mental illness had a direct and substantial bearing upon what he knew, or thought he knew, to be the facts when he pulled the trigger; this lay at the heart of the matter.

The trial court’s exclusion was all the more severe because it barred from consideration on the issue of mens rea all this evidence, from any source, thus preventing Clark from showing he did not commit the crime as defined by Arizona law. Quite apart from due process principles, we have held that a bar of this sort can be inconsistent with the Confrontation Clause. See Delaware v. Van Arsdall, 475 U. S. 673 (1986). In Van Arsdall the Court held a state court erred in making a ruling that “prohibited all inquiry into” an event. Id., at 679. At issue was a line of defense questioning designed to show the bias of a prosecution witness. In the instant case the ruling in question bars from consideration all testimony from all witnesses necessary to present the argument that was central to the whole case for the defense: a challenge to the State’s own proof on an element of the crime. The Due Process and Compulsory Process Clauses, and not the Confrontation Clause, may be the controlling standard; but the disability imposed on the accused is every bit as substantial and pervasive here as it was in Van Arsdall.

Arizona’s rule is problematic because it excludes evidence no matter how credible and material it may be in disproving an element of the offense. The Court’s cases have noted the potential arbitrariness of per se exclusions and, on this rationale, have invalidated various state prohibitions. See Holmes, supra, at 329 (rule excluding, in certain cases, evidence that a third party may have committed the crime *792“even if that evidence, if viewed independently, would have great probative value and even if it would not pose an undue risk of harassment, prejudice, or confusion of the issues”); Rock, supra, at 56 (rule excluding all hypnotically refreshed testimony “operates to the detriment of any defendant who undergoes,hypnosis, without regard to the reasons for it, the circumstances under which it took place, or any independent verification of the information it produced”); Washington v. Texas, 388 U. S. 14, 22 (1967) (rule excluding accomplice testimony “prevent[s] whole categories of defense witnesses from testifying on the basis of a priori categories that presume them unworthy of belief”).

This is not to suggest all general rules on the exclusion of certain types of evidence are invalid. If the rule does not substantially burden the defense, then it is likely permissible. See Scheffer, 523 U. S., at 316-317 (upholding exclusion of polygraph evidence in part because this rule “does not implicate any significant interest of the accused”); id., at 318 (Kennedy, J., concurring in part and concurring in judgment) (“[S]ome later case might present a more compelling case for introduction of the testimony than this one does”). Where, however, the burden is substantial, the State must present a valid reason for its per se evidentiary rule.

In the instant case Arizona’s proposed reasons are insufficient to support its categorical exclusion. While the State contends that testimony regarding mental illness may be too incredible or speculative for the jury to consider, this does not explain why the exclusion applies in all cases to all evidence of mental illness. “A State’s legitimate interest in barring unreliable evidence does not extend to per se exclusions that may be reliable in an individual case.” Rock, supra, at 61. States have certain discretion to bar unreliable or speculative testimony and to adopt rules to ensure the reliability of expert testimony. Arizona has done so, and there is no reason to believe its rules are insufficient to avoid *793speculative evidence of mental illness. See Ariz. Rules Evid. 403, 702 (2006). This is particularly true because Arizona applies its usual case-by-case approach to permit admission of evidence of mental illness for a variety of other purposes. See, e. g., State v. Lindsey, 149 Ariz. 472, 474-475, 720 P. 2d 73, 75-76 (1986) (en banc) (psychological characteristics of molestation victims); State v. Hamilton, 177 Ariz. 403, 408-410, 868 P. 2d 986, 991-993 (App. 1993) (psychological evidence of child abuse accommodation syndrome); Horan v. Industrial Common of Ariz., 167 Ariz. 322, 325-326, 806 P. 2d 911, 914-915 (App. 1991) (psychiatric testimony regarding neurological deficits).

The risk of jury confusion also fails to justify the rule. The State defends its rule as a means to avoid the complexities of determining how and to what degree a mental illness affects a person’s mental state. The difficulty of resolving a factual issue, though, does not present a sufficient reason to take evidence away from the jury even when it is crucial for the defense. “We have always trusted juries to sort through complex facts in various areas of law.” United States v. Booker, 543 U. S. 220, 289 (2005) (Stevens, J., dissenting in part). Even were the risk of jury confusion real enough to justify excluding evidence in most cases, this would provide little basis for prohibiting all evidence of mental illness without any inquiry into its likely effect on the jury or its role in deciding the linchpin issue of knowledge and intent. Indeed, Arizona has a rule in place to serve this very purpose. See Rule 403.

Even assuming the reliability and jury-confusion justifications were persuasive in some cases, they would not suffice here. It does not overcome the constitutional objection to say that an evidentiary rule that is reasonable on its face can be applied as well to bar significant defense evidence without any rational basis for doing so. In Van Arsdall, for example, the Court rejected the application of Delaware Rule of Evidence 403, which allows relevant evidence to be excluded *794where its probative value is substantially outweighed by the risk of unfair prejudice or other harms to the trial process. 475 U. S., at 676, and n. 2. While the Rule is well established and designed for a legitimate function, the Constitution prevented an application that deprived the defendant of all inquiry into an important issue. Id., at 679. Other cases have applied this same ease-specific analysis in deciding the legitimacy of an exclusion. See, e. g., Rock, 488 U. S., at 62 (the “circumstances present an argument for admissibility of petitioner’s testimony in this particular case, an argument that must be considered by the trial court”); Chambers v. Mississippi, 410 U. S. 284, 302 (1973) (“In these circumstances, where constitutional rights directly affecting the ascertainment of guilt are implicated, the hearsay rule may not be applied mechanistically to defeat the ends of justice”); cf. Scheffer, supra, at 318 (Kennedy, J., concurring in part and concurring in judgment).

The Court undertakes little analysis of the interests particular to this case. By proceeding in this way it devalues Clark’s constitutional rights. The reliability rationale has minimal applicability here. The Court is correct that many mental diseases are difficult to define and the subject of great debate. See ante, at 774-775. Schizophrenia, however, is a well-documented mental illness, and no one seriously disputes either its definition or its most prominent clinical manifestations. The State’s own expert conceded that Clark had paranoid schizophrenia and was actively psychotic at the time of the killing. See App. 254-257. The jury-confusion rationale, if it is at all applicable here, is the result of the Court’s own insistence on conflating the insanity defense and the question of intent. Considered on its own terms, the issue of intent and knowledge is a straightforward factual question. A trier of fact is quite capable of weighing defense testimony and then determining whether the accused did or did not intend to kill or knowingly kill a human being who was a police officer. True, the issue can be diffi*795cult to decide in particular instances, but no more so than many matters juries must confront.

The Court says mental-illness evidence “can easily mislead,” ante, at 776, and may “tel[l] us little or nothing about the ability of the defendant to form mens rea,” ante, at 775. These generalities do not, however, show how relevant or misleading the evidence in this case would be (or explain why Arizona Rule of Evidence 403 is insufficient for weighing these factors). As explained above, the evidence of Clark’s mental illness bears directly on mens rea, for it suggests Clark may not have known he was killing a human being. It is striking that while the Court discusses at length the likelihood of misjudgment from placing too much emphasis on evidence of mental illness, see ante, at 773-778, it ignores the risk of misjudging an innocent man guilty from refusing to consider this highly relevant evidence at all. Clark’s expert, it is true, said no one could know exactly what was on Clark’s mind at the time of the shooting. See ante, at 777. The expert testified extensively, however, about the effect of Clark’s delusions on his perceptions of the world around him, and about whether Clark’s behavior around the time of the shooting was consistent with delusional thinking. This testimony was relevant to determining whether Clark knew he was killing a human being. It also bolstered the testimony of lay witnesses, none of which was deemed unreliable or misleading by the state courts.

For the same reasons, the Court errs in seeking support from the American Psychiatric Association’s statement that a psychiatrist may be justifiably reluctant to reach legal conclusions regarding the defendant’s mental state. See ante, at 777-778. In this very ease, the American Psychiatric Association made clear that psychiatric evidence plays a crucial role regardless of whether the psychiatrist testifies on the ultimate issue: “Expert evidence of mental disorders, presented by qualified professionals and subject to adversarial testing, is both relevant to the mental-state issues raised by *796mens rea requirements and reliable.... Such evidence could not be condemned wholesale without unsettling the legal system’s central reliance on such evidence.” Brief for American Psychiatric Association et al. as Amici Curiae 15.

Contrary to the Court’s suggestion, see ante, at 776, the fact that the state and defense experts drew different conclusions about the effect of Clark’s mental illness on his mental state only made Clark’s evidence contested; it did not make the evidence irrelevant or misleading. The trial court was capable of evaluating the competing conclusions, as factfinders do in countless cases where there is a dispute among witnesses. In fact, the potential to mislead will be far greater under the Court’s new evidentiary system, where jurors will receive observation evidence without the necessary explanation from experts.

The fact that mental-illness evidence may be considered in deciding criminal responsibility does not compensate for its exclusion from consideration on the mens rea elements of the crime. Cf. ante, at 773-774. The evidence addresses different issues in the two instances. Criminal responsibility involves an inquiry into whether the defendant knew right from wrong, not whether he had the mens rea elements of the offense. While there may be overlap between the two issues, “the existence or nonexistence of legal insanity bears no necessary relationship to the existence or nonexistence of the required mental elements of the crime.” Mullaney v. Wilbur, 421 U. S. 684, 706 (1975) (Rehnquist, J., concurring).

Even if the analyses were equivalent, there is a different burden of proof for insanity than there is for mens rea. Arizona requires the defendant to prove his insanity by clear and convincing evidence. See Ariz. Rev. Stat. Ann. § 13— 502(C) (West 2001). The prosecution, however, must prove all elements of the offense beyond a reasonable doubt. See Mullaney, supra, at 703-704; In re Winship, 397 U. S. 358, 364 (1970). The shift in the burden on the criminal responsibility issue, while permissible under our precedent, see Le*797land v. Oregon, 343 U. S. 790 (1952), cannot be applied to the question of intent or knowledge without relieving the State of its responsibility to establish this element of the offense. See Sandstrom v. Montana, 442 U. S. 510, 524 (1979) (jury instruction that had the effect of placing the burden on the defendant to disprove that he had the requisite mental state violates due process). While evidentiary rules do not generally shift the burden impermissibly, where there is a right to have evidence considered on an element of the offense, the right is not respected by allowing the evidence to come in only on an issue for which the defendant bears the burden of proof. See Cool v. United States, 409 U. S. 100, 103 (1972) (per curiam) (jury instruction that allowed jury to consider accomplice’s testimony only if it was true beyond a reasonable doubt “places an improper burden on the defense and allows the jury to convict despite its failure to find guilt beyond a reasonable doubt”); Martin v. Ohio, 480 U. S. 228, 233-234 (1987) (State can shift the burden on a claim of self-defense, but if the jury were disallowed from considering self-defense evidence for purposes of deciding the elements of the offense, it “would relieve the State of its burden and plainly run afoul of Winship’s mandate”). By viewing the Arizona rule as creating merely a “presumption of sanity (or capacity or responsibility),” ante, at 771, rather than a presumption that the mens rea elements were not affected by mental illness, the Court fails to appreciate the implications for Winship.

The State attempts to sidestep the evidentiary issue entirely by claiming that its mental-illness exclusion simply alters one element of the crime. The evidentiary rule at issue here, however, cannot be considered a valid redefinition of the offense. Under the State’s logic, a person would be guilty of first-degree murder if he knowingly or intentionally killed a police officer or committed the killing under circumstances that would show knowledge or intent but for the defendant’s mental illness. To begin with, Arizona law does *798not say this. And if it did, it would be impermissible. States have substantial discretion in defining criminal offenses. In some instances they may provide that the accused has the burden of persuasion with respect to affirmative defenses. See Patterson v. New York, 432 U. S. 197, 210 (1977). “But there are obviously constitutional limits beyond which the States may not go in this regard.” Ibid. If it were otherwise, States could label all evidentiary exclusions as redefinitions and so evade constitutional requirements. There is no rational basis, furthermore, for criminally punishing a person who commits a killing without knowledge or intent only if that person has a mental illness. Cf. Robinson v. California, 370 U. S. 660, 666 (1962). The State attempts to bring the instant case within the ambit of Montana v. Egelhoff, 518 U. S. 37 (1996); but in Egelhoff the excluded evidence concerned voluntary intoxication, for which a person can be held responsible. Viewed either as an evidentiary rule or a redefinition of the offense, it was upheld because it “comports with and implements society’s moral perception that one who has voluntarily impaired his own faculties should be responsible for the consequences.” Id., at 50 (plurality opinion). An involuntary mental illness does not implicate this justification.

Future dangerousness is not, as the Court appears to conclude, see ante, at 778-779, n. 45, a rational basis for convicting mentally ill individuals of crimes they did not commit. Civil commitment proceedings can ensure that individuals who present a danger to themselves or others receive proper treatment without unfairly treating them as criminals. The State presents no evidence to the contrary, and the Court ought not to imply otherwise.

The State gains little support from Fisher v. United States, 328 U. S. 463 (1946). There the defendant requested an instruction from the trial court that the jury consider his mental deficiencies in determining his capacity for premeditation and deliberation. Id., at 470. The Court noted that *799“[i]n view of the status of the defense of partial responsibility in the District and the nation no contention is or could be made of the denial of due process.” Id., at 466. This dictum may be attributable to the fact that the cases recognizing a defendant’s evidentiary rights and the prosecution’s duty to prove all elements beyond a reasonable doubt were still decades away. It may also reflect the fact that the jury instructions as given did seem to allow the jury to consider evidence of mental deficiency if it disproved the elements of the offense. See id., at 467, n. 3 (The jury instructions stated, “Tt is further contended that even if sane and responsible, there was no deliberate intent to kill, nor in fact any actual intent to kill. Therefore if not guilty by reason of insanity, the defendant at most is guilty only of second degree murder or manslaughter’ ”). Even further ambiguity comes from the fact that the defense in Fisher concerned a claim that the petitioner was “mentally somewhat below the average” with a “psychopathic personality” of aggression. Id., at 467. This general claim of mental deficiencies was relevant to the “theory of partial responsibility,” id., at 470, he wanted the jury to consider. Unlike the mental illness here, though, which concerns inadequacy of perception and information processing, the petitioner’s claim may not have been relevant to mens rea unless mens rea were redefined to include an element of responsibility. Fisher’s language, then, does not control this case.

While Arizona’s rule is not unique, either historically or in contemporary practice, this fact does not dispose of Clark’s constitutional argument. To the extent Fisher may have suggested the contrary, subsequent cases make clear that while the existence of the rule in some jurisdictions is a significant factor to consider, see Egelhoff, supra, at 43 (plurality opinion), it is not dispositive for evaluation of a claim that the accused was foreclosed from introducing evidence crucial to the defense. The evidentiary exclusion of accomplice testimony the Court invalidated in Washington was, in fact, *800well established. See 388 U. S., at 21-22. The exclusion of hypnotically refreshed testimony likewise had some support when the Court held it unconstitutional as applied to a defendant’s own testimony. Rock, 483 U. S., at 57. While 13 States still impose significant restrictions on the use of mental-illness evidence to negate mens rea, a substantial majority of the States currently allow it. Brief for United States as Amicus Curiae 22-23, and n. 13. The fact that a reasonable number of States restrict this evidence weighs into the analysis, but applying the rule as a per se bar, as Arizona does, is so plainly unreasonable that it cannot be sustained.

Putting aside the lack of any legitimate state interest for application of the rule in this case, its irrationality is apparent when considering the evidence that is allowed. See Washington, supra, at 22 (“The absurdity of the rule is amply demonstrated by the exceptions that have been made to it”). Arizona permits the defendant to introduce, for example, evidence of “behavioral tendencies” to show he did not have the required mental state. See Mott, 187 Ariz., at 544, 931 P. 2d, at 1054; Christensen, 129 Ariz., at 35-36, 628 P. 2d, at 583-584. While defining mental illness is a difficult matter, the State seems to exclude the evidence one would think most reliable by allowing unexplained and uncategorized tendencies to be introduced while excluding relatively well-understood psychiatric testimony regarding well-documented mental illnesses. It is unclear, moreover, what would have happened in this case had the defendant wanted to testify that he thought Officer Moritz was an alien. If disallowed, it would be tantamount to barring Clark from testifying on his behalf to explain his own actions. If allowed, then Arizona’s rule would simply prohibit the corroboration necessary to make sense of Clark’s explanation. In sum, the rule forces the jury to decide guilt in a fictional world with undefined and unexplained behaviors but without mental illness. This rule has no rational justification and *801imposes a significant burden upon a straightforward defense: He did not commit the crime with which he was charged.

These are the reasons for my respectful dissent.

*256Doris, J.

The sole issue presented by this appeal is whether this court should abandon the M’Naghten test in favor of a new standard for determining the criminal responsibility of those who claim they are blameless by reason of mental illness.1 State v. Johnson, 119 R.I. 749, 383 A.2d 1012, 1013 (1978). For the reasons stated herein, we have concluded that the time has arrived to modernize our rule governing this subject.

Before punishing one who has invaded a protected interest, the criminal law generally requires some showing of culpability in the offender. The requirement of a mens rea, or guilty mind, is the most notable example of the concept that before punishment may be exacted, blameworthiness must be demonstrated. That some deterrent, restraint, or rehabilitative purpose may be served is alone insufficient. It has been stated that the criminal law reflects the moral sense of the community. “The fact that the law has, for centuries, regarded certain wrongdoers as improper subjects for punishment is a testament to the extent to which that moral sense has developed. Thus, society has recognized over the years that none of the three asserted purposes of the criminal law — rehabilitation, deterrence, and retribution — is satisfied when the truly irresponsible, those who lack substantial capacity to control their actions, are punished.” United States v. Freeman, 357 F.2d 606, 615 (2d Cir. 1966). The law appreciates that those who are substantially unable to restrain their conduct are, by definition, incapable of being *257deterred and their punishment in a correctional institution provides no example for others.

The law of criminal responsibility has its roots in the concept of free will. As Mr. Justice Jackson stated:

“How far one by an exercise of free will may determine his general destiny or his course in a particular matter and how far he is the toy of circumstance has been debated through the ages by theologians, philosophers, and scientists. Whatever doubts they have entertained as to the matter, the practical business of government and administration of the law is obliged to proceed on more or less rough and ready judgments based on the assumption that mature and rational persons are in control of their own conduct.” Gregg Cartage & Storage Co. v. United States, 316 U.S. 74, 78-80, 62 S.Ct. 932, 935, 86 L.Ed. 1283, 1288 (1942).

Our law proceeds from this postulate and seeks to fashion a standard by which criminal offenders whose free will has been sufficiently impaired can be identified and treated in a manner that is both humane and beneficial to society at large. The problem has been aptly described as distinguishing between those cases for which a correctional-punitive disposition is appropriate and those in which a medical-custodial disposition is the only kind that is legally permissible. See Model Penal Code, §4.01, Comment at 156 (Tent. Draft. No. 4, 1955).

Because language is inherently imprecise and there is a wide divergence of opinion within the medical profession, no exact definition of “insanity” is possible. Goldstein, The Insanity Defense 87 (1967). Every legal definition comprehends elements of abstraction and approximation that are particularly difficult to apply in marginal cases. Our inability to guarantee that a new rule will always be infallible, however, cannot justify unyielding adherence to an outmoded standard, sorely at variance with contemporary medical and legal knowledge. Any legal standard designed to assess criminal responsibility must satisfy several objectives. *258It must accurately reflect the underlying principles of substantive law and community values while comporting with the realities of scientific understanding. The standard must be phrased in order to make fully available to the jury such psychiatric information as medical science has to offer regarding the individual defendant, yet be comprehensible to the experts, lawyers, and jury alike. Finally, the definition must preserve to the trier of facts, be it judge or jury, its full authority to render a final decision. See United States v. Smith, 404 F.2d 720, 726 (6th Cir. 1968); Bethea v. United States, 365 A.2d 64, 76 (D.C.Ct.App. 1976). These considerations are paramount in our consideration of the rule to be applied in this jurisdiction in cases in which the defense of lack of criminal responsibility due to a mental illness is raised.

I

The historical evolution of the law of criminal responsibility is a fascinating, complex story. For purposes of this opinion, however, an exhaustive historical discussion is unnecessary; a brief sketch will therefore suffice. The renowned “right-wrong” test had antecedents in England as early as 1582. In that year the Eirenarcha, written by William Lambard of the Office of the Justices of Peace, laid down as the test or criminal responsibility “knowledge of good or evil.” See United States v. Currens, 290 F.2d 751, 764 (3dCir. 1961). During the 1700’s the language of the test shifted its emphasis from “good or evil” to “know.” See United States v. Freeman, 357 F.2d at 616. During the eighteenth century, when these tests and their progeny were evolving, psychiatry was hardly a profession, let alone a science. Belief in demonology and witchcraft was widespread and became intertwined with the law of responsibility. So eminent a legal scholar as Blackstone adamantly insisted upon the existence of witches and wizards as late as the later half of the eighteenth centruy. Biggs, The Guilty Mind 61-62 (1955). The psychological theories of phrenology and monomania thrived and influenced the development of the “right *259and wrong” test.2 Both of these compartmentalized concepts have been soundly rejected by modern medical science which views the human personality as a fully integrated system. By historical accident, however, the celebrated case of Daniel M’Naghten froze these concepts into the common law just at the time when they were beginning to come into disrepute. See generally id. at 81-107.

Daniel M’Naghten attempted to assassinate Sir Robert Peel, Prime Minister of England, but mistakenly shot Peel’s private secretary instead. This assassination had been preceded by several attempts on the lives of members of the English Royal House, including Queen Victoria herself. When M’Naghten was tried in 1843 the jury was charged with a test heavily influenced by the enlightened work of Dr. Isaac Ray who was severely critical of the “right and wrong” rule. See Ray, Medical Jursiprudence of Insanity (1838). After the jury acquitted M’Naghten the public indignation, spearheaded by the Queen, was so pronounced that the Judges of England were summoned before the House of Lords to justify their actions. In an extraordinary advisory opinion, issued in a pressure-charged atmosphere, Lord Chief Justice Tindal, speaking for all but one of the 15 judges, reversed the charge used at trial and articulated what has become known as the M’Naghten rules. See, e.g., United States v. Freeman, 357 F.2d at 617; United States v. Currens, 290 F.2d at 763-64; Biggs, supra at 95-102; Glueck, Mental Disorder and the Criminal Law 162-163 (1925). The principal rule in M’Naghten’s Case, 8 Eng. Rep. 718 (1843) states:

“To establish a defense on the ground of insanity it must be clearly proved that, at the time of committing *260the act, the party accused was laboring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing, or if he did know it, that he did not know that what he was doing was wrong.” 8 Eng. Rep. at 722.

This dual-pronged test, issued in response to the outrage of a frightened Queen, rapidly became the predominant rule in the United States.

This jurisdiction has long adhered to the M’Naghten standard for determining criminal responsibility. In State v. Quigley, 26 R.I. 263, 58 A. 905 (1904), this court intimated that the dual-pronged test of M’Naghten was the prevailing view in Rhode Island. Yet, in State v. Andrews, 86 R.I. 341, 134 A.2d 425 (1957), where we expressly adopted M’Naghten, reference was made only to the knowledge of “right and wrong” portion of that test. Id. at 352, 134 A.2d at 432. Although it has not always been clear whether the “nature and quality” component of M’Naghten is included as part of the formal rule in this jurisdiction,3 compare State v. Page, 104 R.I. 323, 332, 244 A.2d 258, 263 (1968) and State v. Jefferds, 91 R.I. 214, 216, 162 A.2d 536, 538 (1960) with State v. Nault, 112 R.I. 687, 690, 314 A.2d 627, 629 (1974), as a matter of practice expert witnesses testify concerning both parts of the rule. See State v. Page, 104 R.I. at 332, 244 A.2d at 263. Unlike several other jurisdictions, Rhode Island has never augmented M’Naghten with the “irresistible impulse doctrine.”

*261II

The M’Naghten rule has been the subject of considerable criticism and controversy for over a century. See generally United States v. Currens, 290 F.2d at 765-66. The test’s emphasis upon knowledge of right or wrong abstracts a single element of personality as the sole symptom or manifestation of mental illness. M’Naghten refuses to recognize volitional or emotional impairments, viewing the cognitive element as the singular cause of conduct. See United States v. Freeman, 357 F.2d at 618; Durham v. United States, 214 F.2d 862, 871-72 (D.C.Cir. 1954); Glueck, supra at 226-27, 428-29. One scholar has stated that:

“[t]he principle behind M’Naghten, namely, that defect of cognition as a consequence of mental disease is the primary exculpating factor in the determination of legal insanity, has probably never been other than a legal fiction.” Diamond, From M’Naghten to Currens, and Beyond, 50 Calif.L.Rev. 189, 189 (1962).

M’Naghten has been further criticized for being predicated upon an outmoded psychological concept because modern science recognizes that “insanity” affects the whole personality of the defendant, including the will and emotions. Durham v. United States, 214 F.2d at 871; Royal Commission on Capital Punishment, Report 80, (1953). One of the most frequent criticisms of M’Naghten has been directed at its all- or-nothing approach, requiring total incapacity of cognition. See Wade v. United States, 426 F.2d 64, 71 (9th Cir. 1970); People v. Drew, 22 Cal.3d 338, 337, 583 P.2d 1318, 1322, 149 Cal.Rptr. 275, 279 (1978); Hill v. State, 252 Ind. 601, 607, 251 N.E.2d 429, 432 (1969). We agree that:

“Nothing makes the inquiry into responsibility more unreal for the psychiatrist than limitation of the issue to some ultimate extreme of total incapacity, when clinical experience reveals only a graded scale with marks along the way. * * *

“The law must recognize that when there is no black and *262white it must content itself with different shades of gray.” Model Penal Code, §4.01, Comment at 158 (Tent. Draft No. 4, 1955).

By focusing upon total cognitive incapacity, the M’Naghten rule compels the psychiatrist to testify in terms of unrealistic concepts having no medical meaning. Instead of scientific opinions, the rule calls for a moral or ethical judgment from the expert which judgment contributes to usurpation of the jury’s function as decision maker. See United States v. Currens, 290 F.2d at 767; Weihofen, Mental Disorder as a Criminal Defense 65 (1954).

Probably the most common criticism of M’Naghten is that it severely restricts expert testimony, thereby depriving the jury of a true picture of the defendant’s mental condition. See, e.g., United States v. Freeman, 357 F.2d at 620; Hill v. State, 252 Ind. at 606, 251 N.E.2d at 432. This contention has been seriously questioned by some commentators who find no support for the argument that M’Naghten inhibits the flow of testimony on the responsibility issue. Goldstein, supra, at 53; accord, Matthews, Mental Disability and the Criminal Law 44-46 (1970). As a matter of practice in this jurisiction, expert testimony under M’Naghten has been unrestricted and robust. Nevertheless, we are convinced that this testimony would be more meaningful to the jury were it not for the narrow determination demanded by M’Naghten.

That these criticisms have had a pronounced effect is evidenced by the large and growing number of jurisdictions that have abandoned their former allegiance to M’Naghten in favor of the Model Penal Code formulation. See notes at 6 & 7 infra. We also find these criticisms persuasive and agree that M’Naghten’s serious deficiencies necessitate a new approach.4

*263III

Responding to criticism of M’Naghten as a narrow and harsh rule, several courts supplemented it with the “irresistible impulse” test. E.g., Parsons v. State, 81 Ala. 577, 2 So. 854 (1886); See Annot. Irresistible Impulse as an Excuse for Crime, 173 A.L.R 391 (1948); Keedy, Irresistible Impulse as a Defense in the Criminal Law, 100 U.Pa.L.Rev. 956 (1952). Under this combined approach, courts inquire into both the cognitive and volitional components of the defendant’s behavior. Although a theoretical advance over the stringent right and wrong test, the irresistible impulse doctrine has also been the subject of wide-spread criticism. Similar to M’Naghten’s absolutist view of capacity to know, the irresistible impulse is considered in terms of a complete destruction of the governing power of the mind. See United States v. Frazier, 458 F.2d 911, 917 (8th Cir. 1972); United States v. Freeman, 357 F.2d at 620. A more fundamental objection is that the test produces the misleading notion that a crime impulsively committed must have been perpetrated in a sudden and explosive fit. Thus, the irrestible impulse test excludes those “far more numerous instances of crimes committed after excessive brooding and melancholy by one who is unable to resist sustained psychic compulsion or to make any real attempt to control his conduct.” Id. at 620-21; see United States v. Smith, 404 F.2d at 725.

The most significant break in the century-old stranglehold of M’Naghten came in 1954 when the Court of Appeals for the District of Columbia declared that, “an accused is not criminally responsible if his unlawful act was the product of *264mental disease or mental defect.” Durham v. United States, 214, F.2d 862, 874-75 (D.C.Cir. 1954). The “product” test, first pioneered by the Supreme Court of New Hampshire in State v. Pike, 49 N.H. 399, 402 (1869), was designed to facilitate full and complete expert testimony and to permit the jury to consider all relevant information, rather than restrict its inquiry to data relating to a sole symptom or manifestation of mental illness. Durham generated voluminous commentary and made a major contribution in recasting the law of criminal responsibility. In application, however, the test was plagued by significant deficiencies. The elusive, undefined concept of productivity posed serious problems of causation and gave the jury inadequate guidance. United States v. Freeman, 357 F.2d at 621. Most troublesome was the test’s tendency to result in expert witnesses’ usurpation of the jury function. As a result, in Washington v. United States, 390 F.2d 444, 455-56 (D.C. Cir. 1967), the court took the extreme step of proscribing experts from testifying concerning productivity altogether. Finally, in United States v. Brawner, 471 F.2d 969 (D.C. Cir. 1972), the court abandoned Durham, decrying the “trial by label” that had resulted. Id. at 977. The author of Durham, Chief Judge Bazelon, stated that testimony couched in terms of the legal conclusion that an act was or was not the product of mental disease invited the jury to abdicate its responsibility as ultimate decision maker and acquiesce in the experts’ conclusions. Id. at 1017 (Bazelon, C.J., concurring & dissenting).

Several commentators have advocated abolition of the separate defense of lack of criminal responsibility due to a mental illness. See, e.g., Dershowitz, Abolishing the Insanity Defense; The Most Significant Feature of the Administration’s Criminal Code-An Essay, 9 Crim.L.Bull. 434 (1973); Goldstein & Katz, Abolish the “Insanity Defense” — Why Not?, 72 Yale L.J. 853 (1963). Proponents contend that abolition would result in the responsibility issue being more properly considered as the existence vel non of the mens rea. Under a common proposal the criminal process would be bifurcated; first, the jury would resolve the question of guilt, *265and second, a panel of experts would determine, the appropriate disposition. Arguably, abolition of the, separate defense is subject to constitutional objections because it potentially abrogates the right to trial by jury and’ offends the guarantee of due process. We believe that such a drastic measure, if advisable at all, is appropriately left to the legislative process. Accord., United States v. Browner, 471 F.2d at 985; Bethea v. United States, 365. A.2d at 73 n.19.

IV

Responding to the criticism of the M’Naghten and irresistible impulse rules, the American Law Institute incorporated a new test of criminal responsibility into its Model Penal Code.5 The Model Penal Code has received widespread and evergrowing acceptance. It has been adopted with varying degrees of modification in 26 states6 *266and by every federal court of appeals that has addressed the issue.7 Although no definition can be accurately described as the perfect or ultimate pronouncement, we believe that the Model Penal Code standard represents a significant, positive improvement over our existing rule. Most importantly, it acknowledges that volitional as well as cognitive impairments must be considered by the jury in its resolution of the responsibility issue. The test replaces M’Naghtens unrealistic all-or-nothing approach with the concept of “substantial” capacity. Additionally, the test employs vocabulary sufficiently in the common ken that its use at trial will permit a reasonable three-way dialogue between the law-trained judges and lawyers, the medical-trained experts, and the jury. See United States v. Brawner, 471 F.2d at 983.

Without question the essential dilemma in formulating any standard of criminal responsibility is encouraging a maximum informational input from the expert witnesses while preserving to the jury its role as trier of fact and ultimate decision maker. As one court has aptly observed:

“At bottom, the determination whether a man is or is not held responsible for his conduct is not a medical but a legal, social or moral judgment. Ideally, psychiatrists *267— much like experts in other fields — should provide grist for the legal mill, should furnish the raw data upon which the legal judgment is based. It is the psychiatrist who informs as to the mental state of the accused — his characteristics, his potentialities, his capabilities. But once this information is disclosed, it is society as a whole, represented by judge or jury, which decides whether a man with the characteristics described should or should not be held accountable for his acts.” United States v. Freeman, 357 F.2d at 619-20.

Because of our overriding concern that the jury’s function remain inviolate, we today adopt the following formulation of the Model Penal Code test:

A person is not responsible for criminal conduct if at the time of such conduct, as a result of mental disease or defect, his capacity either to appreciate the wrongfulness of his conduct or to conform his conduct to the requirements of law is so substantially impaired that he cannot justly be held responsible.

The terms “mental disease or defect” do not include an abnormality manifested only by repeated criminal or otherwise antisocial conduct.8

There are several important reasons why we prefer this formulation. The greatest strength of our test is that it clearly *268delegates the issue of criminal responsibility to the jury, thus precluding possible usurpation of the ultimate decisioniby the expert witnesses. Under the test we have adopted, the jury’s attention is appropriately focused upon the legal and moral aspects of responsibility because it must evaluate the defendant’s blameworthiness in light of prevailing community standards. Far from setting the jury at large, as in the majority Model Penal Code test the defendant must demonstrate a certain form of incapacity. That is, the jury must find that a mental disease or defect caused a substantial impairment of the defendant’s capacity to appreciate the wrongfulness of his act or to conform his conduct to legal requirements. Our new test emphasizes that the degree of “substantial” impairment required is essentially a legal rather than a medical question. Where formerly under M’Naghten total incapacity was necessary for exculpation, the new standard allows the jury to find that incapacity less than total is sufficient. Because impairment is a matter of degree, the precise degree demanded is necessarily governed by the community sense of justice as represented by the trier of fact.

Several other components of our new test require elucidation. Our test consciously employs the more expansive term “appreciate” rather than “know.” Implicit in this choice is the recognition that mere theoretical awareness that a certain course of conduct is wrong, when divorced from appreciation or understanding of the moral or legal impact of behavior, is of little import. See United States v. Freeman, 357 F.2d at 623. A significant difference from our former rule is inclusion in the new test of the concept that a defendant is not criminally responsible if he lacked substantial capacity to conform his conduct to the requirements of law. As we noted at the outset, our law assumes that a normal individual has the capacity to control his behavior; should an individual manifest free will in the commission of a criminal act, he must be held responsible for that conduct. Mental illness, however, can effectively destroy an individual’s capacity for choice and impair behavioral controls.

*269The drafters of the Model Penal Code left to each jurisdiction a choice between the terms “wrongfulness” and “criminality.” We prefer the word “wrongfulness” because we believe that a person who, knowing an act, to be criminal, committed it because of a delusion that the act was morally justified, should not be automatically foreclosed from raising the defense of lack of criminal responsibility.9

The second paragraph of our test is designed to exclude from the concept of “mental disease or defect” the so-called psychopathic or sociopathic personality. See Model Penal Code, §4.01, Comment at 160, (Tent. Draft. No. 4, 1955). We have included this language in our test to make clear that mere recidivism alone does not justify acquittal. See United States v. Freeman, 357 F.2d at 625; Bethea v. United States, 365 A.2d at 80-81. We recognize that this paragraph has been the source of considerable controversy. See, e.g., Wade v. United States, 426 F.2d 64, 72-73 (9th Cir. 1970); United States v. Smith, 404 F.2d at 727, n.8; Diamond,. From M’Naughten to Currens, and Beyond, 50 Calif. L. Rev. 189, 194 (1962). Nevertheless, we believe that its inclusion in our test is necessary to minimize the likelihood of the improper exculpation of defendants who are free of mental disease but who knowingly and deliberately pursue a life of crime.10

V

As we have emphasized previously, preserving the respective provinces of the jury and experts is an important concern. Consonant with modern medical understanding, *270our test is intended to allow the psychiatrist to place before the jury all of the relevant information that is must consider in reaching its decision. We adhere to Dean Wigmore’s statement that when criminal responsibility is in issue, “any and all conduct of the person is admissible in evidence.” 2 Wigmore, Evidence §228 (1940). Nevertheless, the charge to the jury must include unambiguous instructions stressing that regardless of the nature and extent of the experts’ testimony, the issue of exculpation remains at all times a legal and not a medical question. In determining the issue of responsibility the jury has two important tasks. First, it must measure the extent to which the defendant’s mental and emotional processes were impaired at the time of the unlawful conduct. The answer to that inquiry is a difficult and elusive one, but no more so than numerous other facts that a jury must find in a criminal trial. Second, the jury must assess that impairment in light of community standards of blameworthiness. The jury’s unique qualifications for making that determination justify our unusual deference to the jury’s resolution of the issue of responsibility. See United States v. Eichberg, 439 F.2d 620, 624-25 (D.C. Cir. 1971) (Bazelton, C.J., concurring & dissenting). For it has been stated that the essential feature of a jury “lies in the interposition between the accused and his accuser of the commonsense judgment of a group of laymen, and in the community participation and shared responsibility that results from that group’s determination of guilt or innocence.” Williams v. Florida, 399 U.S. 78, 100, 90 S.Ct. 1893, 1906, 26 L.Ed.2d 446, 460 (1970). Therefore, the charge should leave no doubt that it is for the jury to determine: 1) the existence of a cognizable mental disease or defect, 2) whether such a disability resulted in a substantial impairment at the time of the unlawful conduct of the accused’s capacity either to appreciate the wrongfulness of his conduct or to conform his conduct to the requirements of the law, and consequently, 3) whether there existed a sufficient relationship between the mental abnormality and the condemned behavior to warrant the *271conclusion that the defendant cannot justly be held responsible for his acts.

VI

So there will be no misunderstanding of the thrust of this opinion, mention should be made of the treatment to be afforded individuals found lacking criminal responsibility due to a mental illness under the test we have adopted. Unquestionably the security of the community must be the paramount interest. Society withholds criminal sanctions out of a sense of compassion and understanding when the defendant is found to lack capacity. It would be an intolerable situation if those suffering from a mental disease or defect of such a nature as to relieve them from criminal responsibility were to be released to continue to pose a threat to life and property. The General Laws provide that a person found not guilty because he was “insane”11 at the time of the commission of a crime shall be committed to the Director of the State Department of Mental Health for observation. At a subsequent judicial hearing if he is found to be dangerous, the person must be committed to a public institution for care and treatment. G.L. 1956 (1968 Reenactment) §26-4-4. This procedure insures society’s protection and affords the incompetent criminal offender necessary medical attention.

Our test as enunciated in this opinion shall apply to all trials commenced after the date of this opinion. The defendant in the instant case is entitled to a new trial solely on the issue of criminal responsibility.

The defendant’s appeal is sustained and the case is remanded to the Superior Court for a new trial in accordance with the opinions expressed herein.

*272Dennis J. Roberts II, Attorney General, Nancy Marks Rahmes, Special Assistant Attorney General, E. Martin Stutchfield, Special Assistant Attorney General, for plaintiff.

Cappuccio <Lr Cappuccio, Frank S. Cappuccio, William F. Reilly, Public Defender, Barbara Hurst, Chief Appellate Attorney, Lise J. Gescheidt, Assistant Public Defender - Amicus Curiae, for defendant.