It seems important to ensure justice, not revenge. Here in the US we still have the death penalty--something that is not a deterrent and is often applied to innocent people. In the end that is revenge, not justice. If a person remains a danger to others, that person needs to be kept away from others. The trouble is determining whether a person is still a danger. There have been clear cases in the US where a young person kills someone, is sentenced to death, then after years in jail is clearly reformed, yet is still murdered by the state. And yes, I consider the death penalty to be state-sanctioned murder.