Double jeopardy

The Double Jeopardy Clause of the Fifth Amendment says no person shall "be subject for the same offence to be twice put in jeopardy of life or limb." It protects against a second prosecution for the same offense after acquittal, a second prosecution after conviction, and multiple punishments for the same offense in the same case. It applies to the states under the Fourteenth Amendment.

Jeopardy generally "attaches" when a jury is sworn or, in a bench trial, when the first witness is sworn. A mistrial or a successful defense appeal usually permits retrial, but an acquittal cannot be appealed by the prosecution. Whether two charges are the "same offense" is determined by the Blockburger test, asking whether each requires proof of a fact the other does not.

Under the dual sovereignty doctrine, reaffirmed in Gamble v. United States (2019), separate governments such as a state and the federal government may each prosecute the same conduct because each is a separate sovereign. Critics, including some conservatives and libertarians, argue this undercuts the clause's purpose. The doctrine bears on high-profile cases involving grand jury indictments and habeas corpus review.