Double jeopardy

Double jeopardy is a procedural defence that prevents an accused person from being tried again on the same (or similar) charges following a valid acquittal or conviction.

If this issue is raised, evidence will be placed before the court, which will normally rule as a preliminary matter whether the plea is substantiated; if it is, the projected trial will be prevented from proceeding. In some countries certain exemptions are permitted, such as in the United Kingdom, where in Scotland a new trial can be initiated if, for example, the acquitted has made a credible admission of guilt, and in England and Wales, where serious offences may be re-tried following an acquittal if new and compelling evidence is found and for the trial to be in the public's interest.

Double jeopardy used by Agatha Christie

 * The Mysterious Affair at Styles
 * Witness for the Prosecution (1957 film)