This is one of many examples that the Prison/correctional system is unable to rehabilitate, in fact it almost seems that it's making a petty thief or small time criminal become a insane & senseless monster. Then again this man may have been senseless all his life. You might ask yourself if getting hit in the head in shovel could be used in defense for pleading insanity. Please see the lecture Mark Twain, The New Crime....
http://etext.lib.virginia.edu/etcbin/toccer-new2?id=TwaCrim.sgm&images=images/modeng&data=/texts/english/modeng/parsed&tag=public&part=1&division=div1
http://etext.lib.virginia.edu/etcbin/toccer-new2?id=TwaCrim.sgm&images=images/modeng&data=/texts/english/modeng/parsed&tag=public&part=1&division=div1