These developments make it almost impossible to prevail in an insanity defense. In New York, the insanity defense is listed in Penal Code Section 40.15. In the section, the law states “[i]n any prosecution for an offense, it is an affirmative defense that when the defendant engaged in the proscribed conduct, he lacked criminal responsibly by reason of mental disease or defect. Such lack of criminal responsibility means that at the time of such conduct, as a result of mental disease or defect, he lacked substantial capacity to know or appreciate either (1) the nature or consequences of such conduct; or (2) that such conduct was wrong.” If you compare this to the M’Naghten rule, you can see that it’s basically the same.
It is very difficult to prevail under the M’Naghten rule because you would be hard-pressed to find a situation in which a person doesn’t think that committing murder is wrong, even if they are insane. For example, in the Tarloff case, Mr. Tarloff was under the impression that his mother was being mistreated in a nursing home. He also thought he was in direct communication with God and God was telling him to commit a robbery to get money so that he can pay for his mother to live in Hawaii. The victim, a psychologist, died brutally because the robbery was botched. It appears that Mr. Tarloff was sincere in the belief that he was in conversation with God. However, under the New York rule, that’s not enough. The jurors in the case clearly must’ve thought that Mr. Tarloff knew what he was doing was wrong, even if God was telling him to do it. They appear to have relied on evidence presented by the prosecution that Mr. Tarloff planned the robbery and even tried to get away with the murder after it occurred.
What’s interesting to me though is that if you genuinely believe that God is telling you to do something which you would otherwise have thought is morally wrong, then doesn’t God’s edict to commit the act negate the immorality? For example, suppose God went through with his command to Abraham to kill his firstborn son. Would Abraham’s conduct then be immoral if he did it? After all, don’t most people believe that God is the ultimate arbiter of right and wrong? It seems to me that if a person genuinely believes God is commanding him to do something he was raised to believe was wrong and he commits the act as a result of God’s command, then he would be considered insane under the M’Naghten rule. Apparently, the Manhattan jury seems to have disagreed.