The same difficulty exists in scripture. God commands the death as a punishment but also says “vengeance is mine.”

That said, it’s clear to me capital punishment is a remedial good.

Not to scandalize anyone, but Francis’s revision to the catechism is terribly flawed and should be removed. It cites “new understandings” which is not how doctrine develops.

”We have high security prisons that keep them out of society.”

No we don’t. The prisoners in the prison are also in society. Are we supposed to keep maniacs in solitary indefinitely?

“It’s an attack on human dignity!”

No, not rendering someone their due (justice) is an attack on their dignity.

“We need to give them time to repent!”

Consequentialism. The ends don’t justify the means.

Besides if a child rapist was truly repentant, he would accept death.