Claim Preclusion (Res Judicata) vs. Issue Preclusion (Collateral Estoppel)
A detailed comparison of these two civil procedure rules, including key differences, exam strategies, and guidance on when to apply each.
Overview
Claim preclusion and issue preclusion are the two branches of the broader res judicata doctrine. Both prevent relitigation, but they operate at different levels of generality and have different requirements. Understanding the distinction is essential for civil procedure exams and practice.
Claim preclusion (res judicata in the narrow sense) bars a party from bringing any claim that was or could have been raised in a prior action between the same parties that ended in a valid final judgment on the merits. The doctrine requires: (1) a final judgment on the merits in the prior action, (2) the same parties or their privies, and (3) the same claim or cause of action (with most courts using a transactional test, meaning all claims arising from the same transaction or occurrence). Claim preclusion is broad: it bars not only claims actually litigated but also claims that could have been raised.
Issue preclusion (collateral estoppel) bars relitigation of a specific factual or legal issue that was actually litigated, actually decided, and essential to the judgment in a prior action. Unlike claim preclusion, it does not require the same claim; it can apply in a subsequent action involving a different claim as long as the specific issue was resolved in the first action. Mutuality of parties was traditionally required, but modern doctrine allows non-mutual issue preclusion in many jurisdictions, where a non-party to the first action can use the prior judgment defensively (and sometimes offensively, per Parklane Hosiery Co. v. Shore).
Key Differences
| Aspect | Claim Preclusion (Res Judicata) | Issue Preclusion (Collateral Estoppel) |
|---|---|---|
| What is barred | The entire claim or cause of action, including unraised theories | Only the specific issue that was actually litigated and decided |
| Same claim required? | Yes, must involve the same transaction or occurrence | No, can apply across different claims if the same issue arises |
| Actually litigated? | Not required; bars claims that could have been raised | Required; only bars issues actually litigated and decided |
| Mutuality of parties | Same parties or privies required | Modern law allows non-mutual preclusion in many jurisdictions |
| Essential to judgment | Not a separate requirement | The issue must have been essential (necessary) to the prior judgment |
Exam Tips
On a civil procedure exam, check claim preclusion first. If the second action involves the same claim between the same parties, claim preclusion bars the entire suit and you do not need to reach issue preclusion. If claim preclusion does not apply (different claim or different parties), then analyze issue preclusion for any overlapping issues. For issue preclusion, the key requirements are that the issue was actually litigated, actually decided, and essential to the prior judgment. Do not forget to address mutuality: if the party seeking to use issue preclusion was not a party to the first action, discuss whether the jurisdiction allows non-mutual preclusion and whether it is defensive or offensive.
When to Apply Which
Apply claim preclusion when the second lawsuit involves the same parties and arises from the same transaction or occurrence as the first. Apply issue preclusion when the second lawsuit involves a different claim (or different parties) but a specific factual or legal issue from the first case is being relitigated. Claim preclusion is the broader doctrine that can bar an entire suit; issue preclusion is narrower and targets specific issues. Use claim preclusion as your first line of analysis, then fall back to issue preclusion if needed.