I don't personally think that there is anything here that's 100% certain other than having a lot of people worked up.
I can see comments from both camps above with interesting logic. i.e. the bit by Math Campbel stating that two wrongs don't make a right could equally be used to justify a complete "no punishment is right system." Ethically I can't agree with this line of reasoning. Two wrongs don't make a right, however, the ideal can not be applied to any workable system.
As a thought, if you were to use as an argument that person A stole a pack of gum from the store and thus did a wrong to the store owner and society by breaking a law, shouldn't suffer any punishment whatsoever citing two wrongs don't make a right, I can only see bad things coming about if our legal system were to adhere to that ideal.
When a society makes a law, the judicial system has to determine how to enforce it in such a way as to where it serves society. At the very core that is the idea behind a justice system that is separate from a legislative system. In order to function society must have a means of protecting itself.
As for punishment, specifically capital punishment, I just am undecided about what to think about it. I do know that there are times where for the "good of society" death might be required. Imagine this, Ghandi was / is a wonderful human being, yet technically upon being thrown in prison, he gained power and influence (rightly so) and eventually effected great change.
What if there was a moral opposite of Ghandi in a human being? What if Hitler was imprisoned after World War 2 and not executed? Could he have eventually effected change in the opposite direction that Ghandi did? He certainly had a lot of followers and his moral compass was completely gone. So in those extreme cases where no matter how good a prison is, the prisoner inside becomes powerful to those on the outside this would be an instance where "society must protect itself" could have a viable argument.
What of Polpot? House arrest for extreme mass murder and ethical cleansing. Was this a better solution than what we did with Hitler? Would we as a society have been okay with cleaning up the death camps knowing that the diseased mind that created Auschwitz was living in a house just down the road?
Thought of it another way, what to do with bin laden? One day this will be a question for all civilized society. As a religious leader, would it not be impossible to hold him in any prison without inspiring further acts of terror by his followers still on the outside in vain attempts to have him freed?
I abhore the death penalty, morally I can't understand how anyone could want their society to actively kill people. Yet, logically I can't find a way around it as there are cases where society, in order to function, must be able to protect itself. As such if it is right for society to protect itself in the extreme cases, then the only question remains do we trust our courts enough to wield the power to end someone's life? It is them after all that we as a society rely upon to judge both the extreme and mundane cases alike.
I don't know how to ask our judges, juries, police, and lawyers to judge fairly with the power of death in their hands. Such a decision can never and should never be an easy one. Yet I don't know if it is possible a case can never be made for society to need them to have that exact extreme power.
I look forward to hearing replies to this. As this is a topic I am honestly undecided on.