The
ancient common law prohibition on multiple trials, known as the double jeopardy
principle or its Latin equivalent nemo debet bis vexari, is a procedural
defence that prohibits the prosecution of an accused for a criminal offence for
which he has already been acquitted or convicted following a trial on the
merits by a court of competent criminal jurisdiction. A peremptory plea of autrefois acquit or
autrefois convict may be entered meaning the defendant was formerly acquitted
or convicted of the same (or substantially the same) offence. When the pleas in bar are raised, evidence
will be placed before the court, which will normally rule as a preliminary
matter whether the plea is substantiated, and if it so finds, the projected
trial will be estopped. Double jeopardy can only arise when there has been a
previous criminal trial. In many countries,
the protection against double jeopardy is a constitutional right while in
others it is afforded by statute law. Statutory
modification of the principle in England and Wales has been the model for
reform in several common law jurisdictions, which allow post-acquittal retrials
in limited circumstances where new and compelling evidence emerges or where
there acquittal is tainted. This article
critically evaluates double jeopardy law reform in Ireland in the light of
reforms in England and Wales and possible implications for the trial of
offences in the Irish criminal justice process.