Helter Skelter: The True Crime Classic and Definitive Account of the Manson Murders

by Vincent Bugliosi

In most states, including California, the legal test of insanity is the M’Naghten Rule. Among other things, M’Naghten provides that if a defendant, as a result of mental disease or defect, does not realize that what he did was wrong, then he is legally insane. It is not enough, however, that he personally believe his acts were not wrong. Were this so, every man would be a law unto himself. For instance, a man could rape a dozen women, say, “I don’t think it’s wrong to rape.” and therefore evade criminal punishment. The clincher is whether he knows that society thinks his actions are wrong. If he does, then he cannot be legally insane. And deliberate acts to avoid detection—such as cutting telephone wires, eradicating prints, changing identities, disposing of incriminating evidence—constitute circumstantial evidence that the defendant knows society views his acts as wrong.