In jurisprudence, double jeopardy is a procedural defence (primarily in common law jurisdictions) that prevents an accused person from being tried again on the same (or similar) charges following an acquittal or conviction and in rare cases prosecutorial and/or judge misconduct in the same jurisdiction. Double jeopardy is a common concept in criminal law. In civil law, a similar concept is that of res judicata. Variation in common law countries is the peremptory plea, which may take the specific forms of autrefois acquit ('previously acquitted') or autrefois convict ('previously convicted'). These doctrines appear to have originated in ancient Roman law, in the broader principle non bis in idem ('not twice against the same').
If a double-jeopardy issue is raised, evidence will be placed before the court, which will typically 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. In Scotland a new trial can be initiated if, for example, the acquitted has made a credible admission of guilt. Part of English law for over 800 years, it was partially abolished in England, Wales and Northern Ireland by the Criminal Justice Act 2003 where, following demand for change, serious offences may be re-tried following an acquittal if new and compelling evidence is found, and if the trial is found to be in the public's interest. In some countries, including Canada, Mexico, and the United States, the guarantee against being "twice put in jeopardy" is a constitutional right. In other countries, the protection is afforded by statute.
In common law countries, a defendant may enter a peremptory plea of autrefois acquit ('previously acquitted') or autrefois convict ('previously convicted'), with the same effect.
Double jeopardy is not a principle of international law. It does not apply between different countries, unless having been contractually agreed on between those countries as, for example, in the European Union (Art.
