Death Penalty

The Moussaoui trial got me thinking again about the death penalty. I am generally opposed to the death penalty because I am generally opposed to the state executing people. I can see how in the right circumstances you can make exceptions to the rule through, and I am sympathetic to people who support the death penalty. And in times of war all bets are off.
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But my real question is, is it a penalty at all? Doesn't supposing death is a punishment presuppose the existence of an afterlife. If no afterlife exists aren't you really denying an offender punishment.
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The elements of justice I remember are retribution, specific deterrence, general deterrence and reformation. There could be one more which slips my mind. I'll take them in reverse order.
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Reformation is reeducation. It is the effort to try and reform an offender so that he may either lead a productive life in jail or perhaps in society if he is released. Job training, counseling, these kids of things come to mind. The American justice system and the American people modestly support reform of criminals, but it is not considered the primary focus of incarceration. Now with serious offenders it is unlikely that we would chose to release them, but some reformation might be necessary to keep them functional in a jail environment. Otherwise I don't think reformation is a concern for anyone other than the most liberal minded. Obviously, imposing the death penalty precludes any reformation.
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General deterrence is a message to everyone not in jail. See what happens if you kill someone? You get locked up. Incarceration clearly serves as a message that you shouldn't do a crime. I suppose the death penalty serves the same message. However, if most criminals are poorly educated and/or prone to passion I question whether they will be able to coherently weigh the costs and benefits of committing criminal acts. And I've always questioned, if you are poor and have no prospects don't the benefits of committing a crime outweigh the costs? The worst you can end up with is having no freedom of movement and getting three square meals, well and maybe AIDS, which would suck. I don't know if most sane people would rather rot in jail or die. Don't most people who are vested in the society fear losing a house, a car, their possessions, a revenue stream their spouse and children as much or more than a stay in jail? So I think as far as the death penalty goes it could be a push.
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Specific deterrence prevents the criminal from committing more criminal acts. Clearly, if you are dead the chances of you committing further crimes are slim. If you are alive conceivable you could be released or sprung and return to a life of crime. Or you could even commit crimes in jail. So this seems like the ultimate reason to support the death penalty.
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Finally, retribution. Here is what really confuses me. As demonstrated by Moussaoui, retribution seems to be largely subjective, but for me always slants toward incarceration rather than execution. For some, I can imagine them becoming accustomed to jail or even learning to enjoy it, regardless of the level of hardship. For others I can imagine it being one hardship after another. Now death on the other hand for its punitive aspect is more of a dilemma. Sure death in and of itself is some measure of punishment, and if you fear death then that punishment is magnified. But isn't there an element of theism creeping in to what we view as the vengeful purpose of the death penalty. I hope you die and burn in hell, the movies say. Well what if there is no hell? What if a person just dies and we've missed out on the opportunity to really punish them? I recognize that we've just practiced the ultimate act of specific deterrence, but is that it? Couldn't the death penalty be the act that least punishes the offender as in the case of Moussaoui as much as it could be the act that most punishes him?