I usually try to steer clear of these types of discussions, but I couldn't resisting adding my own two cents here.
It is my humble opinion that taking the life of one innocent individual is one too many. This is the fatal flaw in the death penalty system, and there really isn't any way around it. Sure, DNA evidence might be able to demonstrate someone's innocence (you're supposed to be innocent until proven guilty of course), but that's not infallible. In the first place, the DNA evidence might only be found after the verdict and after the execution. Secondly, DNA evidence isn't always available. Etc.
I imagine that one of the very worst possible feelings is knowing you're going to be executed for a crime you never committed...
Edited by Genomicus, : No reason given.