"Clearly, the Church has no authority to abandon the radical moral distinction between capital punishment of the guilty and the killing of an innocent. To reject that distinction is to undermine belief in divine justice itself, which demands the supernatural death of unrepentant souls for all eternity. It is manifestly impossible for Catholic doctrine on the death penalty to “develop” from an approbation based on revealed truth to a condemnation based on the teaching of the last Pope. And, if we are not discussing the immorality of capital punishment in itself, when all is said and done it is not a question of “development” of doctrine, but only the debatable application of a morally legitimate penalty. Here Catholics, and civil authorities, remain free to make their own prudential judgments."
Christopher A. Ferrara (Can the Church Ban Capital Punishment)