The Church, consistent with Aquinas, regards her duty to guiding society be consistent with what is right and true and good for the whole body of Christ. The death penalty is furthering a culture of death and the Lord commands its abolition.
Wrong. Summa Theologica II II q64 art2
“Our Lord commanded them to forbear from uprooting the cockle in order to spare the wheat, i.e. the good. This occurs when the wicked cannot be slain without the good being killed with them, either because the wicked lie hidden among the good, or because they have many followers, so that they cannot be killed without danger to the good, as Augustine says (Contra Parmen. iii, 2). Wherefore our Lord teaches that we should rather allow the wicked to live, and that vengeance is to be delayed until the last judgment, rather than that the good be put to death together with the wicked.”
Who determines that the death penalty should be withheld because it is detrimental to the common good, other than the human authorities responsible for it? To state it is just ‘
common opinion’ that the death penalty is harming the common good is to detract from the fact that it is the very duty and obligation of the human authorities to make that determination. The Church did not come up with the death penalty and the Church didn’t invent abolition of the death penalty. That has come from society. The reason the Church makes statements is in either defense of the death penalty against a belief that it is intrinsically evil or in defense of abolition against those who claim it is intrinsically just.