If you read even a little about the statistics behind capital punishment, you accept the fact it's a tool of racism as practiced today. If you happen to be racist, you still can't deny that the number of DNA-exonerated "convicts" tells us that, yes, innocent defendents have been and will be killed in our system.
So before one can start in on the "what if your dad had a gun to his head, and you had a bazooka, and ..." straw men, one must determine this:
I accept x number of innocent deaths for every y captial trials. Whatever that number is for the majority of Americans, I can speculate it's a lot lower than reality.
But if you suppose that reforms in adequate representation, fair and equal prosecution, elimination of sloppy labwork, and non-racist juries resulted in a future of extremely rare innocent deaths; you could debate the morality of state executions.
I think Jeanne has it about it right for the pro-death side...
TMW: Jeanne d'Arc:
Yes, we kill people
"This is what you have to believe if you support capital punishment: Monsters are monsters and they know it. (If they seem not to, they must be faking us out, and we have to be tough and not be swayed.) People who loved capital punishment loved Gary Gilmore for supporting their myths. They despised Stanley Williams not, primarily, because of his crimes, but because his life challenged that myth.
I don’t know if the redemption is real or fake. I know there are many people who can’t face the prospect that it might be real, because realizing that the capacity for good and the capacity for evil dwell in the same body is too difficult to face. But to really challenge capital punishment, you have to force people to face it."
When it comes to an individual, and whether or not there is redemption so visible that one can earn a right to a natural death in prison; I doubt most of the pro-death crowd will ever find a single person worthy (see Dubya.) So throw out clemency powers; they're almost never used anyway because of the right's politics on the issue. Let's make it what it really is; death is death, even if Christ himself asks for a life sentence on your behalf.
Would that put pressure on us to change our laws? I don't know. I don't think Americans as a whole give it much thought. How many of us are proud to be part of an Axis of Pro-Death Penalty with China and Iran? My guess? Not many, and far too many.