I've never really understood the insanity plea. Sure, they may be insane, but isn't that just more reason to keep them out of the general population? Maybe with treatment they MIGHT go back to being normal and MIGHT not kill again, but is it really worth the risk?

I can understand mitigating circumstances -- like you walked in on your wife with another man and in the heat of the moment killed somebody -- but not getting off on premeditated murder because you were insane "at the time."