I'm thinking out loud in this post, so please bear with me.
Yesterday I started to think about the similarities and differences between parental punishment of children and the State's legitimate punishment of offenders. While there are, of course, important differences, some of the principles are the same: parents may not be cruel or abusive, the punishment, to be effective, ought to be suitable to the offense, and the punishment should have a twofold purpose: to restore order, and to provide the opportunity for the child to repent and be "rehabilitated" from his infraction.
To look at an example, suppose a child is playing with several other children and begins behaving badly (snatching toys away, pushing, yelling etc.). The mother enters the room, and conducts a sort of "mini trial," in which the infraction is investigated, blame assigned, and the guilty party identified. She then "sentences" the naughty child to sit on a chair by himself in another room for a specific period of time. He does not wish to do this--but he complies, knowing that the punishment will be worse if he does not. When his time of "incarceration" is over he returns to the game, and now the choice is his: to play by the rules and behave himself, or to act up again and risk further punishment.
Now, while the arrest and imprisonment of a grown man or woman is different in many ways, you still have a just authority, a trial to determine the truth, a sentence pronounced, and, usually, a prison sentence or other punishment determined. Again, the punishment is geared toward both justice and mercy, toward both removing the offender from society, the way the child was isolated from his peers, and toward giving the offender the opportunity to repent and be rehabilitated, and thus return to and remain in society.
How does the death penalty fit into this? The way I see it presently (though I'm open to correction), the death penalty is to be used when the State determines that only thus can society really be protected from the offender--that the offender has been an aggressor against innocent life, and has lost all his "chances" of the kind of rehabilitation that will allow him to return to society or even to continue his life among the society of the prison. I may be wrong, but I think it is possible that the death penalty's claim to consider the prisoner and be merciful to him lies in the notion that the final and severest mercy one can have toward the truly incorrigible aggressor is to force him to face his mortality in the light of his crimes and sins. This is not the reason the state may execute; the reason remains only to protect everyone else from this incorrigible aggressor who will not stop attacking and threatening his fellow men. But the Church would not, I think, condone a use of the death penalty which cut off the prisoner from spiritual guidance, from the Sacraments (if he is Catholic), or from similar exhortations to repent before repentance is forever impossible--which, to me, means that mercy to the prisoner is still, if somewhat paradoxically, intended.
But this sentence from CCC 2267 is important, too: "If, however, non-lethal means are sufficient to defend and protect people's safety from the aggressor, authority will limit itself to such means, as these are more in keeping with the concrete conditions of the common good and more in conformity to the dignity of the human person."
From this I get that the Church sees non-lethal means as "...more in conformity to the dignity of the human person..." which implies that the death penalty is necessarily less in conformity to that dignity. Far from being some kind of perfect means of punishment which ought to serve as the standard by which we measure all other means of punishment, the death penalty is a sorrowful necessity caused by our fallen nature, and by the possibility of incorrigible depravity and viciousness that lurks in the human soul.
How does this relate to torture?
I think that some people argue this way:
a) the Church permits the death penalty, to protect society.
b) there are times when torture (or something not-torture that would be torture if it were not justly necessary) would also protect society.
c) Torture (or the not-torture which is exactly like torture) is less extreme than putting someone to death.
d) Therefore, if the extreme of putting someone to death may be used to protect society, it follows that torture (or not-torture) must be permissible if it is being used in limited situations to protect society.
But the way the Church writes about the death penalty, she makes it clear that non-lethal means are "...more in keeping with the concrete conditions of the common good and more in conformity to the dignity of the human person..." than the death penalty is. Like I said, then, the death penalty isn't the "model" of how we ought to punish the guilty--it is something sadly necessary because of our fallenness, but not something to be used indiscriminately, celebrated, or elevated as the standard of Christian punishment.
What should be the standard, to me, are those punishments that are more visibly ordered toward both justice and mercy, toward the protection of society and, simultaneously, toward the possibility of the repentance and rehabilitation of the prisoner.
And this means that so far from seeing a sort of "If the Church permits the death penalty, then the Church must permit torture..." framework, we could instead see it as "Though the Church must permit the death penalty in rare circumstances, we should remain mindful that the ordinary purpose of punishment, formed by considerations of justice and mercy, is to protect society from the aggressor while offering to the prisoner the opportunity for repentance and rehabilitation."