A criminal appeal was a procedure in English law to bring about the prosecution of an individual accused of some crime. A private individual (the "appellor") would accuse another (the "appellee") of a crime, without the need for proceedings to be brought by the crown. It possibly descended from the system of weregild.
Appeals were among the legal proceedings for which trial by combat was available.
An acquittal following an appeal prevented any further prosecution for the same offence (the doctrine of double jeopardy), just as if the proceedings had been brought by the crown (by indictment). The person bringing the appeal would be punished.
Unlike crown prosecutions, if a person was convicted, the crown did not have the option of a pardon.
- William Blackstone, Commentaries on the Laws of England, Book 4, Chapter XXII "Of the several modes of prosecution", Section IV