Pilate.
Also, a ‘No contest’ plea comes in handy for minor offenses, where a person would like to plea out but doesn’t want to say that they did something wrong. It could be a complex case (was that really self-defense?) or something to small to be worth a trial (do you want to pay a lawyer to get you out of a $50 fine?). I understand that no contest pleas are pretty common for misdemeanors and traffic offenses, but are pretty rarely accepted for a plea bargin on more serious crimes.
A plea of “No contest” protects you in case you believe you may also be the target of a civil suit following the criminal suit. For instance, a wrongful death suit by the victim’s family. Pleading “guilty” in the criminal case would almost certainly be used against you in a civil suit.
IANAL, etc.
In the U.S. silence in the face of a direct accusation can be used as evidence against the accused. The cop says to the suspect “We know you killed Mary Roe last night!” and the suspect sits silent. The cop can then testify that the defendant did not deny the accusation and by inference, admits it. Because wouldn’t an innocent person deny his guilt?
IMHO the one and only response one should give to the police in the face of questioning is “I want to speak to an attorney now.”
At this stage of the case the issue is not whether the accused’s mental incapacity is such that he cannot be convicted of an offence, but whether it is such that the cannot be put on trial. The test is whether he is capable of understanding the trial process and of instructing his defence. He is presumed to be fit to stand trial unless the contrary is shown, and if he is charged and the question is raised at his trial it will, as a question of fact, be decided by the jury on the evidence put before them.
So far the only evidence (that we know of) that might be put before a jury on this question is that he refuses to say anything to anyone, although he is known to be capable of speech. This tell us nothing about his capacity to understand the trial and instruct a defence and, if this is the only evidence, then he should not be found unfit to stand trial.
Presumably, however, the authorities know more than we do, and they may suspect that he is in fact unfit. If so, they would rather know this now than charge him, proceed to trial and then have him found unfit.