While the differences between civil, criminal, and administrative proceedings are not always perfectly clear, courts have done a much better job of explaining when jeopardy begins, or attaches. This question is crucial because any action taken by the government before jeopardy attaches, such as dismissing the indictment, will not prevent later proceedings against the same person for the same offense. Once jeopardy has attached, the full array of Fifth Amendment protections against multiple prosecutions and multiple punishments takes hold.

The U. S. Supreme Court has held that jeopardy attaches during a jury trial when the jury is sworn. In criminal cases tried by a judge without a jury, also called a bench trial, jeopardy attaches when the first witness is sworn. Jeopardy begins in juvenile delinquency adjudications when the court first hears evidence. If the defendant or juvenile enters a plea agreement with the prosecution, jeopardy does not attach until the plea is accepted by the court.