"No one should be twice vexed for one and the same cause."

This Latin maxim serves as a safeguard against judicial abuse and ensures fairness in legal proceedings, preventing a person from being subjected to multiple trials or punishments for the same act.

Rooted in Roman law, the principle broadly carries two rules: first, the verdict of the first trial must be consistent with the law; and second, it does not apply when new evidence emerges after the first trial or if the first verdict was obtained by fraud.

In criminal law, it is the foundation of the rule against double jeopardy. In civil law, it gives rise to the doctrine of res judicata — preventing the re-litigation of a matter already decided.