What does the legal doctrine of res judicata prevent in litigation?

The legal doctrine of res judicata, also known as claim preclusion, serves to prevent the re-litigation of claims that have already been decided by a competent court. This principle is rooted in the need for finality in judicial decisions, ensuring that once a court has rendered a judgment on a particular issue or claim, the same parties cannot bring that claim again in future litigation. By doing so, res judicata promotes judicial efficiency and protects the integrity of court decisions.

In contrast, the other options address different aspects of litigation processes. Joining multiple parties pertains to the procedural ability to involve additional parties in a lawsuit, amending complaints relates to the process of modifying the pleadings, and consolidation of actions involves merging two or more lawsuits into a single proceeding. However, none of these processes directly relate to the prevention of re-litigation of claims, which is the core tenet of res judicata.