That's kind of outside my lanes as well.
In general terms, what I believe would happen--but I think you'd be better to ask a lawyer that question--is that the person, even if they had PTSD, would be responsible for their actions. That would not be an excuse. So if they did something, they would be found guilty. However, the circumstances of their illness would be a mitigating influence in any sentencing that would occur.
I believe that is correct, but I would ask that you please check that with the legal authorities.