MBE Rules · Civil Procedure
Collateral estoppel (issue preclusion)
The rule
A party is precluded from re-litigating an ISSUE that was (1) actually litigated, (2) actually determined, (3) essential to the prior judgment, and (4) the party had a full and fair opportunity to litigate. Modern rule allows non-mutual offensive use against a defendant who litigated and lost (Parklane Hosiery).
In plain English
Once a court decides an important issue in a case, you can't argue about that same issue again in a different case if you had a fair chance to argue it the first time.
Worked example
In a car accident case, the court decides Driver A was speeding. In a later lawsuit about damages, Driver A can't argue they weren't speeding because that issue was already decided.
Memory hook
Issue déjà vu: litigate once, skip twice. If you fought and lost on an issue, you can't fight it again in new suits.
The trap
Students think: any issue can be reused. Wrong, because it must be essential to the judgment. The actual test is whether the issue was necessary to the prior decision.
How examiners test it
Test setup: defendant lost on an issue before, new plaintiff tries to use it. Trap: students miss that it must have been essential to the first judgment to apply non-mutual offensive collateral estoppel.
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