I feel the best resolution is to put the perp down in the same manner as he/she took the victim's life.  If the victim died of a gunshot then shoot the perp.; stabbing then stab the  perp  to death; severe beating, so be it, etc., etc.  Then I do not see how the perp can complain at all about "cruel and unusual punishment". I bet that would readily welcome the three juices and end the whole debate.