As far as I remember (it's been a while though) A person has to have capacity to act for it to be considered a crime.
But in a nutshell, the state of insanity allows the capacity to act to not be there, so if his insanity at the time of the act can be proved, he won't have the capacity to be accountable for his actions. Depending on the legal system in use, of course.
But it's a frigging difficult thing to prove.

Proud Sony Rear Admiral







