While the question of whether the death penalty deters crime or not has gone on for a long time, fairly new studies show that the death penalty is indeed a deterrent:
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Now, if the death penalty stops murders, then we have a moral obligation to support it. After all, by banning capital punishment we would be sentencing innocents to death. With mandatory modern DNA evidence the idea that we could sentence an innocent to death is seemingly close to impossible.
While some mild statements critical of capital punishment have come out of the Church as of late, the statements and actions of the Church in the past speak strongly in favor of its usage. I hardly think that Blessed Pope Urban II, who rallied Europe to crush the Seljuk hordes, would utter a word against capital punishment.
I think all of this opposition to the death penalty is a waste of time and would be better spent fighting against the abortion holocaust. While the Catholics who oppose capital punishment and fight against it truly have good and holy intentions, I feel the end result of their efforts would not be good. The innocent children in the womb deserve our resources, not rapists and murderers.
I say that as long as we have solid DNA evidence, let the murderers, rapists, and pedophiles be executed.