It should be noted that, while the double jeopardy protection restricts both state trials and federal trials, it only prevents duplicate criminal trials by the same “sovereign.” In other words, if a suspect is tried by a state court, the 5th Amendment does not protect him from being tried in a federal court for the same offense. It also does not protect him from being tried more than once for the same offence if it falls under the jurisdiction of more than one state.
Although the language of the double jeopardy clause would seem to be absolute, there are several reasons why a case may legitimately be retried. If a defendant appeals, and his conviction is overturned on any grounds other than insufficient evidence, then the case may be retried. If the defendant requests a mistrial before the jury has issued a verdict, and the trial is halted because of his request, then the case can be tried again. And if there is a “hung jury” (where they cannot reach a unanimous decision), or if there is “manifest necessity” for ending a trial before a verdict can be rendered, then a case can be retried.
Moreover, while the Double Jeopardy Clause protects the defendant from being tried for the same offense under a different name, it does not protect someone who has been convicted of assault and battery from later being charged with murder if his victim dies from his wounds after the first conviction.
Finally, it is important to remember that the prohibition against double jeopardy only applies to criminal cases. It does not protect someone from a civil suit brought against a defendant for the same conduct that might also be tried in a criminal court. In 1995, a jury in Los Angeles acquitted O.J. Simpson of the charge of first degree murder of his ex-wife, Nicole Brown Simpson, and her friend, Ronald Goldman. But that criminal trial did not prevent family members of the victims from suing Simpson for “wrongful death.” In the civil suit, the plaintiffs were awarded millions of dollars in damages.