See also Collateral estoppels, Issue preclusion and Res judicata. “It is a principle of general application in Anglo-American jurisprudence that one is not bound by a judgment in personam in a litigation in which he is not designated as a party or to which he has not been made a party by service of process.” Hansberry v. Lee, 311 U. S. 32, 40 (1940). Several exceptions temper this basic rule. In a class action, for example, a person not named as a party may be bound by a judgment on the merits of the action, if she was adequately represented by a party who actively participated in the litigation. See id., at 41.
For a judgment to have the effect of claim preclusion it must be final, on the merits, and valid. Under traditional tests, the first litigation is res judicata only to the same cause of action in a subsequent action. If a plaintiff asserts the same primary right and duty, and the second lawsuit turns on the same evidence as the first, or the legal theory is changed in a second lawsuit against the same defendant, claim preclusion applies. Under modern law, claim ...