Fitness to plead has traditionally been assessed in England and Wales according to the Pritchard Criteria. More recently the case of Jones has been cited.
The Pritchard criteria are generally accepted and are the criteria that most solicitors, barristers and judges are familiar with.
According to the Pritchard Criteria, a defendant will be unfit to plead if s/he is unable to one or more of:
- comprehend the course of proceedings of the trial, so as to make a proper defence
- understand the evidence against them
- instruct their legal representatives
- challenge a juror
The question of fitness to plead is generally raised by the defence, who must prove on the balance of probabilities that the defendant is unfit. If the prosecution raises the issue (which is rare) then they must prove unfitness beyond reasonable doubt.