Yes. Because we can't make a legal distinction between being sure someone is guilty and being really, really, really, really sure someone is guilty.
Based on the number of innocent people on death row who have been exonerated, there is very little doubt in my mind that we have executed an innocent man. That is too high a price to pay for vengeance.
The cost argument is bunk. It costs more to execute a person than to keep him in prison for life because of the cost of appeals. And if you want to take those away, then we will definitely execute innocent men.