The question is whether it is the extent we are going to allow the risk of executing an innocent person. I think that that is a horrible side effect of our system. While the system is run by human beings, I think it will remain fallible. If there is a death penalty, then you can't eliminate the possibility of it being used on an innocent person.
To really have a death penalty that does for us what most death penalty advocates would get from it, what you have to do is accept a higher risk than we already have of executing innocent people.
That’s a stock objection to the death penalty. An obvious counterexample to his objection is the fact that there are many situations in modern life where we routinely risk the lives of innocent people. Policemen and firemen have dangerous jobs. Roofers have dangerous jobs. Electricians have dangerous jobs. Sharing the same road with cars, bicycles, and motorcycles is hazardous to bikers. The list is long.
Much of modern life involves a comparative risk assessment. You can’t eliminate the possibility that innocent people will be killed. Indeed, that’s inevitable.
So there’s a cost/benefit tradeoff. That may sound callous, but that’s a tradeoff we readily accept in many walks of life. Life isn’t risk-free. You take reasonable precautions. But that’s not foolproof.