Section — Wouters, Manual of Moral Theology
Scholion. On Injury to Truth in Confessing
I. Truth, as it is taken here, consists in this: that the penitent declares those things which regard sacramental judgment as they are in conscience. To truth is opposed a lie, by which the penitent, in matter pertaining to sacramental judgment, denies those things which he holds as true or affirms those things which he holds as false.
He does not sin against truth, as it is understood here: 1. who lies about those things which do not pertain to sacramental judgment, for example, if someone falsely says that he is from this or that parish; if he falsely responds about those things concerning which the confessor lacks the right of questioning; 2. who confesses light sins to his usual confessor, but as often as he has committed a grave sin goes to another confessor. If he does this lest he expose himself to danger of keeping back the sin, he acts rightly; but badly, if it happens for this end, that he may sin more freely.
He sins against truth: 1. who confesses sins which he did not commit, or denies those which he perpetrated; 2. who responds falsely about those things concerning which he is rightly questioned by the confessor.
II. As regards the malice of a lie in confession, take these things: a lie in a matter pertaining to sacramental judgment involves a twofold malice, one of lying, the other of sacrilege; of sacrilege indeed, because it inflicts injury on the sacrament. The malice of lying is light. But the malice of sacrilege is grave or light according as the penitent deceives the confessor in a grave or light matter. Hence it is grave, for example, if he confesses a mortal sin not committed as committed, or a certainly committed sin as doubtfully committed, or a doubtfully committed sin as certain, although the latter is rather done from simplicity for greater tranquility and therefore subjectively is excused from grave sin; likewise if he declares a sin not confessed as confessed; likewise if, rightly questioned about a grave matter, he says what is false; if he falsely asserts that he grieves over the sins which he has confessed, even if he has declared only one venial sin, because it concerns a matter, that is, contrition, pertaining to validity, and therefore grave. It is light if the penitent, for example, declares a confessed mortal sin as not yet confessed (St. Alphonsus, VI, 495-497, who nevertheless does not agree as regards the malice of lying).
Question. Whether it is ever licit to use in confession a restriction that is not purely mental.
Response. Negatively, if it concerns a matter about which the confessor rightly questions. Otherwise it must be affirmed: and so if the confessor undeservedly asks, for example, whether the penitent has confessed elsewhere, the penitent can respond "Negatively," understanding underneath, for example, "so that I am bound to tell you that."