Double jeopardy is a procedural defense that prevents a defendant from being tried multiple times on the same or similar charge, following a legitimate acquittal or conviction. The concept of double jeopardy is a longstanding norm in Western legal thought, having roots in both Greek and Roman Law. As a result, the tradition of double jeopardy is present in a great number of modern legal regimes in one form or another. Many countries have codified protections against double jeopardy as a constitutional right, including Canada, India, Israel, Mexico and the United States.
In the common law, a defendant may enter a preemptory plea of double jeopardy, indicating to the court that the defendant had previously been acquitted or convicted of the same offense. Once the issue is raised, evidence will be presented in order to rule as a preliminary matter whether the plea is substantiated and, if it is, the projected trial will not proceed.
Generally, protections against double jeopardy prevent a person from being convicted twice for the same crime based on the same conduct. If a person robs a bank, he cannot be convicted of robbery twice for the same actions. Similarly, a defendant cannot be twice convicted on two different crimes arising from the same conduct unless they are significantly different or designed to prohibit different forms of conduct. For instance, a person may not 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 said robbery. Double jeopardy is related to the theory of collateral Estoppel, which prevents the same parties from relitigating facts that have already been established by a final judgment.
However, double jeopardy does not generally prohibit the government from bringing a civil action against a defendant for the same offense, even after the defendant is acquitted of the crime. Additionally, acquittal in one jurisdiction does not necessarily bar trial in another for the same offense.
How does a lawyer determine whether a defendant is being tried for the same crime twice? Under the U.S.-based Blockburger test, two crimes do not trigger double jeopardy unless each crime requires proof of an additional element that the other crime does not require.
- See, e.g., Ashe v. Swenson, 397 U.S. 436 (1970), available at http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=us&vol=397&invol=436 (stating that collateral estoppel prevented prosecuting an individual for robbing one of six men during a poker game when at a prior trial he was acquitted of robbing one of the other players).