M'Naghten Rule

The M'Naghten Rule says that if the person who committed the crime didn't know it was wrong when they did it they can be considered insane. This rule dates all the way back to 1843 when Daniel M'Naghten in England thought that the prime minister wanted to kill him. M'Naghten attempted to kill the prime minister but ended up shooting his secretary instead. Experts testified that he was psychotic so he was not guilty by reasons of insanity. After backlash, the Lords of Justice finally said that insanity was a defense only if "at the time of the committing of the act, the party accused was labouring under such a defect of reason, from a disease of the mind as not to know the nature and quality of the act he was doing; or, if he did not know it, that he did not know he was doing was wrong" This became known as cognitive insanity. It differs from volitional insanity which is where the person knows it's wrong but can't control themselves. Which law do you think is fair?