In pari delicto is a Latin term meaning "in equal fault". It’s a legal doctrine that bars a plaintiff who has participated in wrongdoing from recovering damages for loss resulting from the wrongdoing.
In contract law, neither party can claim breach of contract by the other if the fault is more or less equal. In criminal law, a defedant who is found equally at fault with other defendants will have difficulty asserting that he/she was induced to commit the crime by another defendant. However, sometimes the defense is sometimes not applied in the interests of protecting the public, such as a suit by someone who sought to gain on trading stocks using inside information which is brought againt the person who gave the inside tip.