This is an issue that I've never been able to pick a clear side with. A few things I could say however....

The death penalty isn't really a deterrent, as most law experts and sociologists agree. When somebody makes the decision to murder another person, they're already mentally at the point of no return. This mind-state is one where killing the person has exceeded all else in importance, and whether they face death penalty or life in prison, they don't want to see one any more than the other. But killing this person if obviously important enough that they'd risk one of those punishments, and their desire to carry through with it has already long exceeded their desire to stay out of prison or the gas chamber.

On the claim that the death penalty is hypocritical, I don't really agree. The argument goes that you're telling people that killing is wrong, then turn around and kill somebody. But the laws on murder aren't so clear-cut as "murder is wrong". Rather, under law murder is wrong because it is not state-sanctioned, not the result of a jury unanimously agreeing to it, and imposed on a person who is innocent and has done nothing to deserve the punishment.