The vast majority of people from poor, broken, disturbed backgrounds choose to obey the law and not become killers.
Making prisons harsher discourages repeat offending. Like I said in another thread if Moat had been in Singapore he would still be in jail now unable to sit down from the thrashing he was given as part of his punishment for assault. He would be facing ample time in jail to realise the error of his ways and the futility of breaking the law.