This is precisely the kind of "absolutist think" that the Left uses constantly--shame on you for falling for it. Gun control---"if it saves just one life" is one example. Banning DDT is another. Since this is an imperfect world, even the best process will sometimes give the wrong answer. All we humans can do is make the best good-faith effort we can devise. And in the case of the death penalty, we have MORE than done so.
What matters is that the cure not be worse than the disease. It is a proven fact that those criminals who kill, will very likely kill again. "Life without benefit of parole" simply puts prison guards and other inmates at higher risk.
I am not against the death penalty, I know that some people just deserve killin (who said that?).
Excellent response.