But you know what it won't do? It won't render Lawrence Russell Brewer one iota less guilty or less deserving of the death penalty. Opponents of capital punishment are extremely selective about the cases they make into public crusades. Strategically that's smart; you don't want to lead your argument with "unsympathetic persons." But logically it's problematic. There is no transitive property that renders one heinous murderer less deserving of punishment simply because some other person was exonerated of murder.
Timothy McVeigh killed 168 people including 19 children. He admitted it. How does doubt in Troy Davis' case make McVeigh less deserving of death?
We hear so much about the innocent people who've gotten off death row -- thank God -- because of new DNA techniques. We hear very little about the criminals who've had their guilt confirmed by the same techniques (or who've declined DNA testing because they know it will remove all doubt). Death penalty opponents are less eager to debate such cases because they want to delegitimize "the system."
And to be fair, I think this logic cuts against one of the death penalty's greatest rationalizations as well: deterrence. I do believe there's a deterrence effect from the death penalty. But I don't think that's anything more than an ancillary benefit of capital punishment. It's unjust to kill a person simply to send a message to other people who've yet to commit a crime. It is just to execute a person who deserves to be executed.
Opponents of the death penalty believe that no one deserves to be executed. Again, it's an honorable position, but a difficult one to defend politically in a country where the death penalty is popular. So they spend all of their energy cherry-picking cases, gumming-up the legal system and talking about "uncertainty."
That's fine. But until they can explain why we shouldn't have a death penalty when uncertainty isn't an issue -- i.e. why McVeigh and Brewer should live -- they'll never win the real argument.