Also known as:non-mutual issue preclusion · nonmutual collateral estoppel
Written by attorneys · grounded in primary & secondary sources — see below
A doctrine permitting a plaintiff who was not a party to earlier litigation to bar a defendant from relitigating an issue that the defendant already litigated and lost in a prior action ending in a final judgment. The issue must have been actually litigated, necessarily decided, and identical to the one now presented. Application is allowed only when doing so is fair and equitable to the defendant under all the circumstances.
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Cases
Casebooks
Course Outlines
How it applies
Common Examples
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Regulator Judgment Invoked by Users
The Federal Data Protection Commission sued StreamHive after a full trial and obtained a judgment with detailed findings that the platform had knowingly misrepresented its data practices. A certified class of users later filed a damages action against StreamHive and moved to treat those findings as established. The court granted the motion after determining that StreamHive had a full and fair opportunity to litigate the misrepresentation issue and that preclusion would not work an inequity.
Government Not Bound by Prior Loss
A private litigant won a judgment against the government on an immigration eligibility issue. In a later nationwide enforcement action, the government sought to relitigate the same eligibility question against a different defendant. The court refused to apply nonmutual issue preclusion against the government, recognizing that its unique litigation volume and nationwide responsibilities make offensive use against it unfair.
United States v. Mendoza464 U.S. 154 (1984)
Common questions
Frequently Asked
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When is offensive nonmutual issue preclusion fair to the defendant?+
Fairness turns on whether the defendant had a full and fair opportunity and strong incentive to litigate the issue in the first action, whether the procedures were comparable, and whether inconsistent judgments or other circumstances would make preclusion inequitable. Courts weigh these factors case by case rather than applying a categorical rule.
Supporting sources
Does the fact that the first action was brought by a government regulator bar later private plaintiffs from using offensive nonmutual issue preclusion?+
No. Courts permit private plaintiffs to invoke findings from government enforcement actions when the defendant had a full and fair opportunity to litigate and preclusion is equitable. The identity of the first plaintiff is relevant only to the fairness inquiry, not as an absolute bar.
Supporting sources
Can differences in stakes or procedural protections between the first and second actions make offensive nonmutual issue preclusion unfair?+
Yes. When the second action exposes the defendant to far greater liability or offers procedural rights such as a jury trial that were unavailable earlier, courts may decline preclusion because the defendant lacked comparable incentive or opportunity in the first proceeding.
Supporting sources
Must the second plaintiff have been able to join the first action for offensive nonmutual issue preclusion to apply?+
No. The possibility of joinder is one factor in the fairness analysis but is not a strict prerequisite. Preclusion remains available when the defendant had every incentive to litigate vigorously and the other fairness considerations support it.
Supporting sources
Civil ProcedureVerdicts and judgments · Effect; claim and issue preclusionUBEFoundational