When I look at this question, honestly the first thing I think is that if a criminal charged with murder is sent to prison, and is later released on 'good behavior', but then continues to kill, the death penalty is what ought to await them when the authorities once again have them in custody.
It is pretty unlikely to happen that a released criminal is going to continue to kill. When it happens the media goes wild and because we get to know so much information about such cases we tend to think it's a common scheme when it really isn't. Ever heard about someone on the news that got released from prison and than never commited a crime again ? Likely not, because it's not spectacular enough.
Also, it's been proven by research that there is no difference in the number of commited murder regarding wether the state supports death penalty or not. There's simply no good in death penalty at all, however you put it.
Daniel, would you seriously just shoot someone down for stepping on your property? Like, in all seriousness?