A meaningless distinction

That would be the question of whether Anders Breivik is insane. Like Ted Kackzynski, he very much wants you to know that he is perfectly sane, although maybe you don't happen to agree with his philosophical and political wisdom. In TK's case, the result at stake was whether he would be injected with lethal poisons or locked up for the rest of his life. In AB's case, it is precisely where he will be locked up. I suppose these questions matter, but the criterion is just silly.

Nobody actually knows what "schizophrenia" is in the first place, or even whether it is a single entity. Very likely it is not, and one way to tell is that anyone who wants to claim that either Breivik or TK has schizophrenia has to claim that he has a special kind in which many of the characteristic symptoms of the disease are absent. But really, who cares? If you don't want to call either of them schizophrenic you can give them some other disease label by virtue of their deviant behavior -- let's say sociopathy -- and inflated opinion of their own importance -- say narcissism. But it appears that the diseases of sociopathy and narcissism don't get you off the criminal hook, while schizophrenia does. Why is that?

If you want to label them as delusional you would have to claim that believing that industrial civilization has been disastrous for humanity, or that Norwegian culture is being degraded by immigrants, is delusional, but that would cover a whole lot of people who are neither criminals nor likely to be considered insane. Alternatively, you could claim that the belief that mailing out bombs or shooting participants in a political party youth camp would help bring about a desired political outcome is  delusional, but that would mean that anybody who engages in similar actions is ipso facto delusional, which means that nobody who does such things can be culpable.

The fact is that for all of us, free will is an illusion. The brain produces behavior; and the development of the brain through the interaction of genetic endowment with the life course of physical environment and social experience produces the state of the brain that produces said behavior. Claiming that one person is culpable because of the specific -- although not actually well-defined -- state his brain happened to arrive at, while another is not because of some different brain state, is just silly. It's a category error.