Fitness to plead applies to jurisdiction United Kingdom
Test
If the issue of fitness to plead is raised, a judge is able to find a person unfit to plead.  This is usually done based on information following a psychiatric evaluation.
In England and Wales the legal test of fitness to plead is based on the ruling of Alderson B. in R v Pritchard. The accused will be unfit to plead if they are unable:to comprehend the course of proceedings on the trial, so as to make a proper defence; or
to know that they might challenge any jurors to whom they may object; or
to comprehend the evidence; or
to give proper instructions to their legal representatives.If the issue is raised by the prosecution, the prosecution must prove beyond reasonable doubt that the defendant is unfit to plead. If the issue is raised by the defence, it need only be proved on the balance of probabilities.In Scotland the test is based on HMA v Wilson, and has two elements: