Res judicata is one of the most important, because it prevents parties from litigating matters decided in prior cases. For example, if plaintiff sues a defendant in one trial court and loses, res judicata should prevent that plaintiff from commencing another suit against the same party hoping for a better result in another court.
The principle of res judicata seeks to promote the fair administration of justice and honesty and to prevent the law from abuse. The principle of res judicata applies when a litigant attempts to file a subsequent lawsuit on the same matter, after having received a judgment in a previous case involving the same parties.