When can a person not be tried again after an acquittal under the double jeopardy clause?

Under the Fifth Amendment to the U.S. Constitution, the double jeopardy clause prohibits the government from prosecuting an individual for the same offense after they have been acquitted.123

For this protection to apply, jeopardy must have already "attached" to the initial proceedings. In U.S. law, this occurs once the jury is sworn in during a jury trial or when the first witness is sworn in during a bench trial. If a case is dismissed or charges are dropped before this point—such as during a preliminary hearing—the government is not barred from initiating new charges for the same offense.1

Additionally, while the clause prevents retrial for the same crime following an acquittal, it does not necessarily bar prosecution for the same criminal act by a different state or nation.1