[Aquinasfan]

My only concern is; doesn't the Catholic Church also oppose the Death Penalty?

That's a tougher issue. The Church has always taught that the death penalty is justifiable in principle. The latest teaching from the pope (pretty much binding) qualifies the old teaching, saying that the death penalty is still justifiable in principle BUT in countries where it is now possible to imprison criminals for life without their being a threat to the public, then the death penalty is unneccessary and should be opposed for prudential reasons.

[Domestic Church]

"it is now possible to imprison criminals for life"

This raises the question of whether the parole boards and other political characters make this impossible.