Every time a major construction project is started the builders know that a certain number of people are likely to die during the process. Whenever a large army unit jumps out of aircraft there is a good chance someone’s parachute will not open. When flu shots are given to a large population a tiny fraction of the recipients will die of reactions to the vaccine. Do we simply stop building skyscrapers, doing divisional maneuvers and giving vaccines because we can’t guarantee perfection? Like those other activities, the justice system must do it’s best to avoid errors. But, we do not abandon activities because we cannot achieve perfection. Properly administered the death penalty is the correct punishment for certain crimes and criminals. Like dropping a cruise missile on top of a terrorist hideout to kill the most evil among us, there may be collateral damage. We must do everything we reasonably can to eliminate it but we must not surrender just because we cannot achieve perfection. Once all the reasonable steps have been taken to ensure the guilt of the most heinous criminals they should be terminated. Life, and death, is filled with uncertainties and chance, and the chance of an innocent man being put to death today is microscopic. To allow the most evil people in the world to live simply because we cannot rule out every hypothetical possibility of error puts others at risk and is simply unjust. Like the contractor who builds a building, the general who orders a training exercise or the doctor who administers a vaccine, those who administer the laws must do everything to assure things go right. But we don’t stop doing what is right because we can’t achieve perfection.
As for the notion that the death penalty is somehow pagan, that is like saying breathing or child bearing is pagan. Certainly pagans did it, so what? Death as a punishment is clearly spelled out as proper in both the old and new testaments. It is certainly provided for in the US Constitution. Those who find religious or constitutional objections to capital punishment are putting a spin on the documents that those who wrote them certainly never intended.