D'ya think tumbleweed brain puppet boy is really evil or really insane? If insane how can we blame him for anything?

Aren't the insane free of blame for they have no control over what they do or say? Are the insane ever put to death for their high crimes and misdemeanors or are they simply put away in an institution forever more? Isn't that the best way to get a perp off the hook? Use the insanity defense?