Subway Cat arrives at a coorect conclusion but tortures logic getting there.
The reason we have jails has nothing to do with Justice whatever we may call it. It is about the right of a society to provide reasonable domestic security to it's citizens. Locking a man up for fifteen years for armed robbery of a convenience store is not justice. However, unless he escapes, he is not a danger to society for those fifteen years. Which of course leads to another question to the original poster. Has the government failed if, during the course of attempted rehabilitation, escapes his detention and murders again, has the government failed in it's duty to defend it's citizens?