Etymology & Origins: Latin for 'a matter judged,' the principle that a case already decided by a competent court cannot be relitigated by the same parties.
In courtroom proceedings, res judicata is typically raised as an affirmative defense in the answer or through a motion to dismiss or motion for summary judgment. The defending party argues that the plaintiff's claims were or could have been raised in a prior action that resulted in a final judgment on the merits. The court examines whether the same parties are involved, whether the same transaction or occurrence gives rise to the claim, and whether a final judgment was previously entered. If all elements are satisfied, the court will dismiss the current action. Attorneys must be precise in identifying the prior judgment and demonstrating the overlap between the prior and current claims.
Attorney: "Your Honor, we move to dismiss under the doctrine of res judicata. The plaintiff litigated this exact claim — arising from the same contract and the same alleged breach — in Case No. 2024-CV-1547, which resulted in a final judgment on the merits in our favor. The plaintiff cannot relitigate claims that have already been decided."
Judge: "Counsel for the plaintiff, can you explain how the current action differs from the prior case? The defendant has made a prima facie showing that the same cause of action between the same parties was resolved by final judgment."
Attorney: "The doctrine of res judicata bars not only claims that were actually raised in the prior proceeding, but also claims that could have been raised. My client should not be forced to defend against piecemeal litigation over the same transaction."
Students frequently confuse res judicata (claim preclusion) with collateral estoppel (issue preclusion). Res judicata bars an entire claim from being relitigated, while collateral estoppel only bars relitigation of specific factual or legal issues that were actually litigated and necessarily decided in the prior action.
Allen v. McCurry, 449 U.S. 90 (1980)
Held that collateral estoppel and res judicata apply to Section 1983 civil rights actions, giving preclusive effect to state court criminal proceedings in subsequent federal civil rights litigation.
Federated Department Stores, Inc. v. Moitie, 452 U.S. 394 (1981)
Reaffirmed that res judicata bars re-litigation of claims that were or could have been raised, even if the prior judgment was arguably erroneous, emphasizing the importance of finality.
Taylor v. Sturgell, 553 U.S. 880 (2008)
Rejected "virtual representation" as a basis for claim preclusion, holding that nonparties may be bound by prior judgments only in six narrowly defined circumstances.
What is res judicata?
Res judicata (claim preclusion) is a doctrine that prevents parties from re-litigating a claim that has already been decided by a final judgment on the merits. Once a court renders a final judgment, the same parties (or their privies) cannot bring a new lawsuit based on the same cause of action. This promotes judicial efficiency and protects parties from repeated litigation.
What are the elements of res judicata?
Res judicata requires: (1) a final judgment on the merits in a prior action, (2) the prior action involved the same parties or their privies, (3) the same cause of action or claim is involved, and (4) the claim was or could have been raised in the prior proceeding. The doctrine bars not only claims actually litigated but also those that should have been raised.
What is the difference between res judicata and collateral estoppel?
Res judicata (claim preclusion) bars re-litigation of an entire claim or cause of action. Collateral estoppel (issue preclusion) bars re-litigation of a specific factual or legal issue that was actually litigated and necessarily decided in a prior proceeding. Res judicata is broader — it bars claims that were or could have been raised — while collateral estoppel is narrower, applying only to issues actually decided.
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