I believe all murderers (excluding those who are engaging in saving the lives of others) are insane.
It is not what sane people do. MURDER their own kind when their lives are not being threatened.
But there are degrees of insanity and it seems to me the ones who the biggest LOST CAUSE nutjobs are those who take pleasure in inflicting great pain on others. TORTURE and then MURDER. They get charged up by it and get off on it. Sexually frustrated I expect they take it out on others with their weapons of destruction.
Those who are sane could never engage in such as that. NEVER.
INSANITY is the defense of course. Or "passion of the moment". Crap.
The question is what do we do about the millions of insane people who are murderers already or murderers in waiting? Let them be what they are? Let them run amok? Let them do their thang? Or CRUSH them?