(1) Though claim preclusion's effects may be harsh at times, its defenders cite numerous policy justifications. According to the Supreme Court, "res judicata and collateral estoppel relieve parties of the cost and vexation of multiple lawsuits, conserve judicial resources, and, by preventing inconsistent decisions, encourage reliance on adjudication." Allen v. McCurry, 449 U.S. 90, 94 (1980).
(2) The "transactional" test from Rush is the most commonly used test for determining a prior judgment's preclusive effect. As the Fifth Circuit described:
. . . the preclusive effect of a prior judgment extends to all rights the original plaintiff had "with respect to all or any part of the transaction, or series of connected transactions, out of which the [original] action arose." . . . What factual grouping constitutes a "transaction," and what groupings constitute a "series," are to be determined pragmatically, giving weight to such considerations as whether the facts are related in time, space, origin, or motivation, whether they form a convenient trial unit, and whether their treatment as a unit conforms to the parties' expectations or business understanding or usage. . . . "[T]he criminal issue is whether the two actions under consideration are based on the same nucleus of operative facts." . . .
Petro-Hunt, L.L.C. v. United States, 365 F.3d 385, 395 - 96 (5th Cir. 2004) (internal citations omitted).
(3) The tests for determining the scope of claim preclusion have evolved over the last century. The comments to the Restatement (Second) of Judgments, published in 1982, describe that evolution. According to the Restatement, "in the days when civil procedure still bore the imprint of the forms of action and the division between law and equity, the courts were prone to associate claim with a single theory of recovery so that, with respect to one transaction, a plaintiff might have as many claims as there were theories of the substantive law upon which he could seek relief against the defendant." For instance, "if it appeared that the defendant had invaded a number of primary rights conceived to be held by the plaintiff, the plaintiff had the same number of claims, even though they all sprang from a unitary occurence. . . . Thus it was held by some courts that a judgment for or against the plaintiff in an action for personal injuries did not preclude an action by him for property damage occasioned by the same negligent conduct on the part of the defendant . . . ." This notion has more or less been rejected today. According to the Restatement, "[t]he present trend is to see claim in factual terms and to make it coterminous with the transaction regardless of the number of substantive theories . . . that may be available to the plaintiff; regardless of the number of primary rights that may have been invaded; and regardless of the variations in the evidence needed to support the theories or rights. The transaction is the basis of the litigative unit or entity which may not be split." See Restatement (Second), Judgments Section 24, comment a (1982).