There's two parts that I'm still not sure about here - a question of moral weight W:
1 * innocent prisoner executed == W * innocent victim of crime
and two epistemic questions, how many innocents X are executed per guilty person, and how many victims Y are saved on average by the disincentive caused by executing one guilty prisoner?
Per guilty person executed, we save Y lives and we are penalized W * X. Is Y > W * X? If so it seems reasonable to keep the death penalty, all things being equal (ignoring the cost of litigation vs. prison time, etc)
Does anyone have sources for what the values of any of these numbers should be?