Res judicata is the generic term for a group of related concepts concerning the conclusive effects given final judgments. Within this general doctrine there are two principal categories: (1) claim preclusion—also known as res judicata; and (2) issue preclusion—also known as collateral estoppel.
These legal doctrines generally preclude litigants from relitigating claims and issues that were previously litigated to a final resolution or judgment.
In Kansas, res judicata, or claim preclusion, prevents parties from relitigating a claim that has already been finally adjudicated in a court of competent jurisdiction. Once a final judgment has been rendered, the same parties cannot bring a lawsuit on the same claim or cause of action again. This principle promotes judicial efficiency and respects the finality of court decisions. Issue preclusion, also known as collateral estoppel, is a related concept that bars the re-litigation of specific issues that were already decided in a previous lawsuit between the same parties. For issue preclusion to apply, the issue must have been actually litigated, necessarily decided, and essential to the final judgment in the first action. Both doctrines are grounded in the public policy of limiting unnecessary litigation and preserving the integrity of judicial decisions. Kansas courts adhere to these principles, which are reflected in the state's case law and procedural rules.