Res Judicata and Collateral Estoppel: Claim and Issue Preclusion in Civil Procedure

Litigation is expensive — for the parties, the courts, and the legal system. Preclusion doctrines prevent parties from relitigating the same disputes over and over. Once a matter has been properly adjudicated, the parties are bound by that result.

There are two distinct preclusion doctrines that 1L civ pro courses cover, and they do different things:

Claim preclusion (res judicata) bars relitigation of an entire claim or cause of action that has already been decided — or that could have been decided — in prior litigation.

Issue preclusion (collateral estoppel) bars relitigation of a specific issue of fact or law that was actually litigated and necessarily decided in prior litigation.

Both doctrines say: you had your chance. But they define 'your chance' very differently.

Res judicata bars a party from bringing the same claim again after a final judgment on the merits. But 'same claim' is broader than most students initially expect.

Under the Restatement (Second) of Judgments — the approach most courts follow — 'same claim' means all claims arising from the same transaction or occurrence. If you sued for breach of contract and won, and you then try to sue for unjust enrichment arising from the same contract, claim preclusion bars the second suit — even though it's a different legal theory. You had to bring all claims from that transaction the first time.

Four elements for claim preclusion to apply: (1) a final judgment on the merits; (2) in a court of competent jurisdiction; (3) between the same parties (or parties in privity); (4) involving the same claim (same transaction or occurrence).

Final judgment on the merits: this is broader than a full trial. Summary judgment, 12(b)(6) dismissal with prejudice, and consent decrees all typically qualify. A dismissal without prejudice does not — that leaves the door open for a refiled suit.

Same parties or privity: the doctrine traditionally required the same parties. A judgment against A does not bind B unless B was in privity with A — meaning they had a sufficiently close legal relationship (employer/employee for acts within the scope of employment, principal/agent, successor corporations, etc.).

Issue preclusion is narrower but more precisely targeted. It bars relitigation of a specific issue — not an entire claim — that was (1) actually litigated; (2) actually decided; (3) necessarily determined as part of the prior judgment; and (4) essential to the prior judgment.

The 'actually litigated' requirement is what distinguishes it from claim preclusion. A claim preclusion bar can apply even to claims that weren't raised in the first lawsuit (you were required to raise them then). Issue preclusion applies only to issues that were genuinely contested and decided in the prior case.

Example: Plaintiff sues Defendant for negligence arising from a car accident. The jury finds Defendant was driving at the speed limit. In a second lawsuit arising from the same accident (a different plaintiff), Defendant can use collateral estoppel to prevent relitigation of whether Defendant was speeding — that issue was actually decided in the first case.

Essentially necessary: the issue must have been necessary to reach the judgment. If the prior case could have been decided on other grounds, issue preclusion may not apply because the court's finding on that issue wasn't required for the outcome.

Traditionally, both claim and issue preclusion required mutuality — the doctrine could only be used against a party who was a party to the prior litigation, and only by another party who was also bound by that judgment.

Modern courts have moved away from strict mutuality for issue preclusion. The current trend allows non-mutual issue preclusion in both directions:

Non-mutual defensive collateral estoppel: A new defendant (who was not in the first lawsuit) uses a prior judgment against the same plaintiff to bar the plaintiff from relitigating an issue the plaintiff already lost. The Supreme Court approved this in Blonder-Tongue Laboratories v. University of Illinois (1971).

Non-mutual offensive collateral estoppel: A new plaintiff (who was not in the first lawsuit) uses a prior judgment for them, binding the same defendant on an issue the defendant already lost. The Supreme Court addressed this in Parklane Hosiery Co. v. Shore (1979), allowing it but giving courts discretion to reject it where it would be unfair — for example, where the prior plaintiff had inconsistent verdicts in multiple lawsuits, or where the new plaintiff could have easily joined the first lawsuit.

Scenario 1 (Claim Preclusion): A plaintiff sues a contractor for breach of contract and wins. The plaintiff later tries to sue the same contractor for fraud arising from the same project. Claim preclusion bars the fraud claim — it arises from the same transaction and should have been raised in the first lawsuit.

Scenario 2 (Issue Preclusion): A driver is convicted of reckless driving in a criminal proceeding. In a subsequent civil lawsuit for personal injury arising from the same accident, can the plaintiff use collateral estoppel to establish the driver was reckless? Possibly — but note that the burden of proof differs. Criminal conviction requires proof beyond a reasonable doubt (higher standard), so a conviction satisfies the civil preponderance standard for the same issue. The converse — using a civil finding to bind a criminal proceeding — would not work because the issue wasn't decided to the higher criminal standard.

Scenario 3 (Non-mutual Offensive): Ten plaintiffs sue a manufacturer for defective products. The first five win. The next five want to use collateral estoppel offensively to bind the manufacturer on the defect issue. The Parklane Hosiery discretionary framework applies — courts consider whether the plaintiffs could have joined the first suit, whether there were inconsistent verdicts, and whether the defendant had adequate incentive to litigate vigorously.