Is a murder more valuable dead, or as a living example to learn what drives people to commit these terrible crimes? It almost seems a disservice to the victims if we can't learn how to stop this happening in the future.
Hmmm, thought about it, I still say top him. Do we really need to know that the guy committed these crimes because he was a nutball? You could still end him and know this is the case.
Honestly for all the cuddly, social experimentation, psychobabbling that goes on in todays justice systems, we still haven't managed to stop evil little buggers from murdering people simply because they enjoy the way it makes them feel.
You will never stop crime, whether it be petty theft, or rape and murder. The population of the world are breeding at an exponential rate, the majority of these kids will grow up and live their lives with no issues, some will be great, some will be scum, studying why someone has a poorly wired melon is not going to remove the scum factor any more than you are going to remove the percentile that becomes something amazing.