What is Double Jeopardy Clause?

Legal Definition
The Double Jeopardy Clause of the Fifth Amendment to the United States Constitution provides: "[N]or shall any person be subject for the same offence to be twice put in jeopardy of life or limb . . . ." The four essential protections included are prohibitions against, for the same offense:

  • retrial after an acquittal;
  • retrial after a conviction;
  • retrial after certain mistrials; and
  • multiple punishment

Jeopardy attaches in jury trial when the jury is empaneled and sworn in, in a bench trial when the court begins to hear evidence after the first witness is sworn in, or when a court accepts a defendant's plea unconditionally. Jeopardy does not attach in a retrial of a conviction that was reversed on appeal on procedural grounds (as opposed to evidentiary insufficiency grounds), in a retrial for which "manifest necessity" has been shown following a mistrial, and in the seating of another grand jury if the prior one refuses to return an indictment.
-- Wikipedia