“Crazy” isn’t a very exact term. If he does indeed hear voices, and is not just making it up as an excuse, then he is almost certainly schizophrenic. However, that determination has to be made by a psychiatrist who is experienced in examining people accused of serious crimes. We certainly don’t have the knowledge or experience to do it, so let’s wait for the experts.
And of course there is one Judge who knows it all, and will judge Levi Aron with emes when the time comes.