paragraph — Noldin, Summa of Moral Theology
§ 7. Defect of Mildness.
158. According to the mind of the Church it is plainly unfitting that he who has shed another's blood, or has cooperated in the killing or mutilation of a man, should represent the person of the most meek Christ, who never injured anyone. Therefore she established an irregularity proceeding from a twofold head: from just war and from judgment of blood. That is called a judgment of blood in which a case is treated that is concluded by the imposed penalty of death or mutilation. This irregularity is usually called from defect of (Christian) mildness: for this defect is contracted only after baptism has been received.
159. Irregularity from judgment of blood. He who in a just judgment concurs directly, proximately, and efficaciously, from public authority, toward the killing (or mutilation) of a man becomes irregular. Although there is no text of law which clearly establishes this irregularity, nevertheless from the practice of the Church its existence cannot be doubted.
A just judgment: for if the judgment is unjust, irregularity is not contracted from defect of mildness, but from the delict of homicide or mutilation.
Toward killing: to incur this irregularity some other penalty is not sufficient, such as flogging, even if joined with the shedding of blood; but killing or mutilation is required, and this really following, even if it is accomplished without the shedding of blood. Nevertheless the penalty of mutilation is no longer inflicted in recent law.
From public authority: for he who kills or mutilates a man by private authority does not become irregular from defect, but from delict.
He concurs directly, proximately, and efficaciously who by his action influences the effect; but he influences the effect by his action who places an action necessary for the judgment, either by conducting the trial, or by rendering the sentence, or by executing it.
a. Therefore, of those who concur in a judgment of blood, whether by reason of the trial, or by reason of the sentence, or by reason of execution, the following become irregular from defect of mildness:
a. The judge pronouncing the sentence of death.
b. The accuser and witness deposing against the accused.
c. The advocate and procurator acting against the accused.
d. Assessors, or at the present time especially jurors, who by their vote concur toward the death of the guilty man.
e. Lictors and executioners themselves, who as ministers of justice put the guilty man to death.
b. Of those who cooperate in some way in a judgment of blood, the following do not become irregular:
a. The prince who made the law concerning a crime to be punished by death, because he concurs only remotely.
b. The jurist who, privately asked whether the accused has merited the penalty of death, replied that according to the laws he is to be punished by death, because he does not act in court nor by public authority.
c. The confessor who accompanies the guilty man to the place of punishment, even if he exhorts him to acquiesce in the sentence, to ascend the ladder, to bend his neck, etc., because he acts outside the judgment and by private authority.
d. Spectators of the fatal execution, even if they are clerics, both because by watching they do not cooperate, and because they act outside the judgment and lack public authority.
160. Irregularity from just war. He who in an offensive just war himself by his own hand kills or mutilates someone (in the sense explained above) becomes irregular.
In a just war: for he who in an unjust war kills or mutilates someone, just like he who by his own authority kills or mutilates another, does not become irregular from defect, but from delict.
Offensive: for he who in a defensive war, even by his own hand, kills or mutilates another does not become irregular, unless he is a cleric, just as neither does he who kills or mutilates an unjust aggressor in order to defend himself. Nevertheless clerics who voluntarily serve as soldiers in a defensive war and kill or mutilate someone become irregular.1
By his own hand: for those who kill or mutilate no one, even if they are present at the battle, indeed even if by words or deeds they add courage to the soldiers, whether they are laymen or clerics, do not become irregular. For against those who themselves kill or mutilate no one, even if they concur physically or morally in a just war toward homicide, the Church has established no irregularity.
1 C. Petitio tua 24 De homicidio (V. 12).