A more thorough explanation:

Definition: Res judicata is a legal principle that means a matter has already been judged and cannot be relitigated.

Overview: Once a court has made a final judgment on a case, the principle of res judicata prevents the same parties from bringing the same cause of action to court again. This principle is also known as claim preclusion.

Examples:

• Bar: If a plaintiff sues a defendant and loses, they cannot sue the same defendant again on the same cause of action.
• Merger: If a plaintiff sues a defendant and wins, they cannot sue the same defendant again on the same cause of action to try to recover more damages.

These examples illustrate how res judicata prevents parties from relitigating the same case over and over again, promoting efficiency and fairness in the legal system.

Policies of Preclusion: Courts uphold the doctrine of res judicata based on several policies, including promoting efficiency, promoting fairness, and avoiding inconsistent adjudication.

Exceptions: Res judicata does not apply to cases dismissed for lack of jurisdiction, improper venue, failure to join a party, or voluntary dismissals. Additionally, res judicata does not apply to co-parties in a case.

Alternative Techniques: In addition to res judicata, there are other techniques that courts use to prevent parties from relitigating the same case, including estoppel and judicial estoppel.

Overall, res judicata is an important legal principle that promotes efficiency and fairness in the legal system by preventing parties from relitigating the same case over and over again.