Res Judicata (Claim Preclusion)

Definition

Res judicata, or claim preclusion, prevents a party from relitigating a claim that was or could have been raised in a prior action between the same parties that resulted in a final judgment on the merits. It requires identity of the parties, a final judgment on the merits in the prior action, and the same claim or cause of action (determined by the transactional test). The doctrine promotes finality, conserves judicial resources, and protects parties from the burden of repeated litigation.

Example

A plaintiff sues for personal injury from a car accident and loses. Under res judicata, the plaintiff cannot file a new lawsuit for property damage arising from the same accident.