in law, protection against the use by the state of certain multiple forms of prosecution.

In general (in countries observing the rule of double jeopardy), a person cannot be convicted twice for the same crime based on the same conduct. If a person robs a bank, he cannot twice be convicted of robbery for the same offense. Nor can he be convicted of two different crimes based upon the same conduct unless the two crimes are defined so as to prohibit conduct of significantly different kinds. Thus, a man cannot be convicted of both murder and manslaughter for the same killing, but he can be convicted of both murder and robbery if the murder arose out of the robbery. The defense of double jeopardy also prevents the state from retrying a person for the same crime after he has been acquitted. Nor can the state voluntarily dismiss a case after trial has begun in order to start over. Acquittal in one state or nation does not, however, always bar trial in another.