Can't the doctrine of double effect be used to justify the death penalty in the same way it can be used "to justify lethal acts of self-defense, lethal acts of combat in war, and the like"? Just as in the case of war, an inevitable consequence of the death penalty will be death. But if the intent of the war or of the use of the death penalty is to preserve and protect the community, then doesn't the doctrine of double effect apply equally to both situations?
It is instructive, I think, that the Catechism's discussion of the death penalty is placed in five paragraph section (2263-2267) under the subheading "Legitimate Defense." (although note that the on-line edition of the Catechism has a separate heading for Capital Punishment). Paragraph 2263 begins: "The legitimate defense of persons and societies is not an exception to the prohibition against the murder of the innocent that constitutes intentional killing." Quoting St. Thomas, it continues, "The act of self-defense, can have a double effect: the preservation of one's own life; and the killing of the aggressor. ... The one is intended, the other is not." 2265 says that "legitimate defense can be not only a right but a grave duty for one who is responsible for the lives of others. The defense of the common good requires that an unjust aggressor be rendered unable to cause harm." This grave duty seems to apply to self-defense, defense of family, war, police action, and the death penalty. Therefore (and again with the admission that I haven't yet read Brugger's book), it seems to me that the Church teaches that the use of the death penalty far from being morally forbidden may actually be a "grave duty" of the state, albeit under circumstances that rarely if ever arise today.
On a personal note, I was somewhat ambivilent about the death penalty until the day Timothy McViegh was sentenced to death. My sense was that far from bringing peace and closure, the sentence actually fanned the flames of hate burning (understandably) inside of many in the Oklahoma City area. Bud Welch, a humble gas station owner, stood as a sign of contradiction. Racked by the pain of losing his only daughter, Julie (to read more about Julie and two other young Catholics who died in the bombing, click here or here), this former supporter of the death penalty has devoted his life to reconciliation - visiting Timothy McVieghs father - and to seeking the abolition of the death penalty. Through Bud's example, I have come to understand why the Church teaches that the use of non-lethal means of punishment "are more in keeping with the concrete conditions of the common good and more in conformity with the dignity of the human person."