Collateral estoppel

Collateral estoppel, also sometimes known as issue preclusion, is a common law doctrine that prevents a person from relitigating an issue. Simply stated, when an issue of fact (as opposed to an issue of law) is decided by a fair and impartial arbiter (usually a jury), then the two parties may not relitigate that in the future. It may be offensive collateral estoppel when it is used by a plantiff to prevent relitigation by a defendant who lost against another plaintiff on the same issue or defensive collateral estoppel when the it is used against the plaintiff regarding issues that were previously litigated against another defendant.

Although it emerged out of civil law, in the United States it has applied to federal criminal law since United States v. Oppenheimer in 1916. In 1970 in Ashe v. Swenson, the United States Supreme Court applied it to double jeopardy to limit prosecution for crimes committed at the same time. Codified at Federal Rules of Civil Procedure, Rule 8(c).

Collateral estoppel is closely related to the concept of res judicata (literally - that which has been decided); res judicata is the doctrine that two parties may not relitigate the same point of law after it has been decided by a judge (they may, however, appeal the decision to a higher court or ask the judge for reargument for a revised decision).