Demonstrative Aids

There are two main types of evidence presented in a trial: demonstrative and substantive. Demonstrative evidence illustrates substantive evidence in a more easily undstood summative format like transripts of an audio recording (Garrett), charts, graphs, maps, or an oral summary of a defendant's criminal history (Wheatfall). In the final case in this section, we'll see how the court deals with the burgeoning practice of video video simulations.

Allen Pugh was convicted of murdering William Delorme by running over him with a car in a parking lot shared by three bars along Arnold Blvd. in Abilene.  Based on the location of the body and types of injuries the victim sustained, police believed he was the victim of vehicular homicide. An accident reconstruction expert took 28 total measurements of various locations at the scene with a rangefinder, including the victim’s body, tire tracks, and buildings.  The investigation led police to the Defendant and his truck, one that appeared recently damaged.  Officers collected the truck and apparent biological samples from its undercarriage that DNA analysis later confirmed belonged to the victim.  A second accident reconstruction expert conducted 15 field acceleration tests using an accelerometer.  He input those data points and the 28 measurements from the first expert into a 3-D computer animation program, overlaid those reference points on a version of Google Earth, and used the DNA results, crime scene pictures, autopsy reports in creating the animations. As part of their evidence against him, the State sought to introduce 4 of these computer animation exhibits as demonstrative aids.

One of the four automated animations depicted the events from the viewpoint of the driver of the defendant’s truck; the other three showed separate long-distance views, one bird’s eye view, a northeast view and a southeast view of the defendant’s truck accelerating across the parking lot, striking and then running over a stationary human figure.  The Trial Court excluded the first-person exhibit because it was too “subjective as to what could be seen from the inside of the vehicle.”  However, the other three computer animations were admitted for demonstrative purposes, and were published to the jury with a contemporaneous limiting instruction. 

The rule of admissibility for demonstrative exhibits (in this case, the computer animations) used to illustrate expert testimony (the crash reconstruction expert’s opinion about what happened) is the same for “any other piece of demonstrative evidence.”  The Court stated that evidence is admissible for demonstrative purposes if the proponent shows 1) it is authentic, 2) relevant and has 3) probative value that is not outweighed by the danger of unfair prejudice.  

By “authentic,” the court means that the expert is properly qualified to give the opinion and the opinion is otherwise accurate.  In our words, the evidence is sponsored by a witness with proper knowledge (“properly qualified expert witness”) who testifies that the exhibit is accurate because it was based on “scientifically reliable methods.” 

Pugh also gives us a clear example of the two questions courts consider when determining whether demonstrative exhibits are relevant: one is to determine whether the exhibit helps the jurors understand the otherwise admissible evidence, and second, whether the exhibit is more probative than prejudicial. The question of relevance for demonstrative exhibits do not stem from the probative value of the exhibit itself - a demonstrative aid does not possess probative value independent from the testimony it demonstrates or illustrates.  Rather, the probative value stems from the demonstrative exhibits ability to helpfully illustrate that otherwise admissible testimony for the jurors.  The Court used the Montgomery factors to determine that the danger of unfair prejudice from the demonstrative exhibit did not substantially outweigh its probative value.  In particular, the human figure depicted in the animation was faceless and expressionless, did not move or react to the truck, remained rigid when struck by the truck, and none of the exhibits depicted any of the victim’s injuries.