My response stands pretty much on its own, though it has probably been said over and over again by others and said more elegantly. Still it must not have been said enough as I see we still have the death penalty.
Comment to KJ:
I have no great moral opposition to your stance on the Death Penalty, but I'm still against it.
Since one can never know with absolute certainty in all cases the guilt of the accused, the Death Penalty is inevitably used with an unavoidable degree of capriciousness. As long as the Death Penalty is an option, the innocent may also be put to death, and those deaths most likely end any further search for the truth (the justice system burying its mistakes). Despite your creation of a "No Doubt" category there will always be doubt and cases on the edge.
Still assuming one could know with certainty, and the case of this soldier probably passes this test, I would be against it for more practical reasons. In the case of terrorists (homegrown or not) you create martyrs for the cause. Should this man or Zacharias Moussoui be put to death, their deaths would be celebrated in radical Muslim circles and probably inspire other to take their place. While keeping them in prison might invite attempts to blackmail for their release, their deaths would more likely inspire what is seen in their supporters' eyes as rightful retribution. I suspect if you took a poll as to the preference of gun toting radicals whether they would prefer life in jail or the death penalty they would enthusiastically vote for the death penalty and the speed with which it takes them to their rewards in Heaven. Granted this mind set might change after getting caught, but my point is the recruiting potential it has for those uncaught.
For an even more practical reason to give up the Death Penalty is the better footing it would put us on with those we consider allies and more clearly distance us morally from those we consider foes. Mexico will not extradite some criminals to the US because of the possible application of the Death Penalty, the same with many European nations. Many in the world see America as barbaric and backward because we haven't given up the death penalty. Even if it is not barbaric, and I don't think it is if you can guarantee certainty, it accomplishes so little in deterrence it is not worth the complications it creates in matters of international extradition.
We do not currently know all the factors that shape a human psyche. Who is to say a poor upbringing or some unseen congenital brain condition would not be mitigating factors in abrogating some of the blame. Still not to get all weepy liberal on you, but what is the point of the Death Penalty? Fairness, Revenge, Deterrence? The first is debatable, the second unworthy, the third proven again and again to be ineffective.
When you argue victims' rights you are arguing revenge. That it may salve some emotional wounds I won't deny. I for one don't think you should kill people just to make other people feel better.
Sure there are they that no doubt deserve to die. My arguments are about the complications and abuses that arise in the system when it is an option and the lack of cooperation it gets us when dealing with other nations.
I respect your opinion and reasons for it. I have no doubt you are a moral person. I have a different opinion, but unlike some shrill voices on my side of the debate, I can respect those on the other.