I'm not going to vote, but I think there are some powerful instincts at play here...
Fair is fair, an eye for an eye and revenge served well as justice before prisons existed... it took the person off the streets anyways...
However, while I know that I would want revenge for the death of a loved one, I would hope that as I know now, that a large part of it could be explained by messy neuro wirings, and I'd hope that in that situation I would realize that. I think the best prevention would be life imprisonment (as in an entire life), and the study of these people by neuroscientists and pyscholigists. I feel that the collected data could one day help identify people highly predisposed to commiting such actions, which would be the best interest of society and perhaps that individual as well. Perhaps one day there will be interventions for those people, as neuroscientists have discovered definite differences between normal people and psychopaths, and are experimenting with drug interventions last I heard.