Summa Th. II-II EN Qu.68 a.2

Whether it is necessary for the accusation to be made in writing?

Objection: 1. It would seem unnecessary for the accusation to be made in writing. For writing was devised as an aid to the human memory of the past. But an accusation is made in the present. Therefore the accusation needs not to be made in writing.
2. Further, it is laid down (Decret. II, qu. viii, can. Per scripta) that "no man may accuse or be accused in his absence." Now writing seems to be useful in the fact that it is a means of notifying something to one who is absent, as Augustine declares (De Trin. x, 1). Therefore the accusation need not be in writing: and all the more that the canon declares that "no accusation in writing should be accepted."
3. Further, a man's crime is made known by denunciation, even as by accusation. Now writing is unnecessary in denunciation. Therefore it is seemingly unnecessary in accusation.

On the contrary It is laid down (Decret. II, qu. viii, can. Accusatorum) that "the role of accuser must never be sanctioned without the accusation be in writing."
I answer that As stated above (Question [67], Article [3]), when the process in a criminal case goes by way of accusation, the accuser is in the position of a party, so that the judge stands between the accuser and the accused for the purpose of the trial of justice, wherein it behooves one to proceed on certainties, as far as possible. Since however verbal utterances are apt to escape one's memory, the judge would be unable to know for certain what had been said and with what qualifications, when he comes to pronounce sentence, unless it were drawn up in writing. Hence it has with reason been established that the accusation, as well as other parts of the judicial procedure, should be put into writing.

Reply to Objection: 1. Words are so many and so various that it is difficult to remember each one. A proof of this is the fact that if a number of people who have heard the same words be asked what was said, they will not agree in repeating them, even after a short time. And since a slight difference of words changes the sense, even though the judge's sentence may have to be pronounced soon afterwards, the certainty of judgment requires that the accusation be drawn up in writing.
2. Writing is needed not only on account of the absence of the person who has something to notify, or of the person to whom something is notified, but also on account of the delay of time as stated above (ad 1). Hence when the canon says, "Let no accusation be accepted in writing" it refers to the sending of an accusation by one who is absent: but it does not exclude the necessity of writing when the accuser is present.
3. The denouncer does not bind himself to give proofs: wherefore he is not punished if he is unable to prove. For this reason writing is unnecessary in a denunciation: and it suffices that the denunciation be made verbally to the Church, who will proceed, in virtue of her office, to the correction of the brother.

Whether an accusation is rendered unjust by calumny, collusion or evasion?

Objection: 1. It would seem that an accusation is not rendered unjust by calumny, collusion or evasion. For according to Decret. II, qu. iii [*Append. Grat. ad can. Si quem poenituerit.], "calumny consists in falsely charging a person with a crime." Now sometimes one man falsely accuses another of a crime through ignorance of fact which excuses him. Therefore it seems that an accusation is not always rendered unjust through being slanderous.
2. Further, it is stated by the same authority that "collusion consists in hiding the truth about a crime." But seemingly this is not unlawful, because one is not bound to disclose every crime, as stated above (Article [1]; Question [33], Article [7]). Therefore it seems that an accusation is not rendered unjust by collusion.
3. Further, it is stated by the same authority that "evasion consists in withdrawing altogether from an accusation." But this can be done without injustice: for it is stated there also: "If a man repent of having made a wicked accusation and inscription* in a matter which he cannot prove, and come to an understanding with the innocent party whom he has accused, let them acquit one another." [*The accuser was bound by Roman Law to endorse (se inscribere) the writ of accusation. The effect of this endorsement or inscription was that the accuser bound himself, if he failed to prove the accusation, to suffer the same punishment as the accused would have to suffer if proved guilty.] Therefore evasion does not render an accusation unjust.

On the contrary It is stated by the same authority: "The rashness of accusers shows itself in three ways. For they are guilty either of calumny, or of collusion, or of evasion."
I answer that As stated above (Article [1]), accusation is ordered for the common good which it aims at procuring by means of knowledge of the crime. Now no man ought to injure a person unjustly, in order to promote the common good. Wherefore a man may sin in two ways when making an accusation: first through acting unjustly against the accused, by charging him falsely with the commission of a crime, i.e. by calumniating him; secondly, on the part of the commonwealth, whose good is intended chiefly in an accusation, when anyone with wicked intent hinders a sin being punished. This again happens in two ways: first by having recourse to fraud in making the accusation. This belongs to collusion [prevaricatio] for "he that is guilty of collusion is like one who rides astraddle [varicator], because he helps the other party, and betrays his own side" [*Append. Grat. ad can. Si quem poenituerit.]. Secondly by withdrawing altogether from the accusation. This is evasion [tergiversatio] for by desisting from what he had begun he seems to turn his back [tergum vertere].

Reply to Objection: 1. A man ought not to proceed to accuse except of what he is quite certain about, wherein ignorance of fact has no place. Yet he who falsely charges another with a crime is not a calumniator unless he gives utterance to false accusations out of malice. For it happens sometimes that a man through levity of mind proceeds to accuse someone, because he believes too readily what he hears, and this pertains to rashness; while, on the other hand sometimes a man is led to make an accusation on account of an error for which he is not to blame. All these things must be weighed according to the judge's prudence, lest he should declare a man to have been guilty of calumny, who through levity of mind or an error for which he is not to be blamed has uttered a false accusation.
2. Not everyone who hides the truth about a crime is guilty of collusion, but only he who deceitfully hides the matter about which he makes the accusation, by collusion with the defendant, dissembling his proofs, and admitting false excuses.
3. Evasion consists in withdrawing altogether from the accusation, by renouncing the intention of accusing, not anyhow, but inordinately. There are two ways, however, in which a man may rightly desist from accusing without committing a sin ---in one way, in the very process of accusation, if it come to his knowledge that the matter of his accusation is false, and then by mutual consent the accuser and the defendant acquit one another---in another way, if the accusation be quashed by the sovereign to whom belongs the care of the common good, which it is intended to procure by the accusation.

Whether an accuser who fails to prove his indictment is bound to the punishment of retaliation?

Objection: 1. It would seem that the accuser who fails to prove his indictment is not bound to the punishment of retaliation. For sometimes a man is led by a just error to make an accusation, in which case the judge acquit the accuser, as stated in Decret. II, qu. iii. [*Append. Grat., ad can. Si quem poenituerit.] Therefore the accuser who fails to prove his indictment is not bound to the punishment of retaliation.
2. Further, if the punishment of retaliation ought to be inflicted on one who has accused unjustly, this will be on account of the injury he has done to someone---but not on account of any injury done to the person of the accused, for in that case the sovereign could not remit this punishment, nor on account of an injury to the commonwealth, because then the accused could not acquit him. Therefore the punishment of retaliation is not due to one who has failed to prove his accusation.
3. Further, the one same sin does not deserve a twofold punishment, according to Nahum 1:9 [*Septuagint version]: "God shall not judge the same thing a second time." But he who fails to prove his accusation, incurs the punishment due to defamation [*Can. Infames, caus. vi, qu. 1], which punishment even the Pope seemingly cannot remit, according to a statement of Pope Gelasius [*Callist. I, Epist. ad omn. Gall. episc.]: "Although we are able to save souls by Penance, we are unable to remove the defamation." Therefore he is not bound to suffer the punishment of retaliation.

On the contrary Pope Hadrian I says (Cap. lii): "He that fails to prove his accusation, must himself suffer the punishment which his accusation inferred."
I answer that As stated above (Article [2]), in a case, where the procedure is by way of accusation, the accuser holds the position of a party aiming at the punishment of the accused. Now the duty of the judge is to establish the equality of justice between them: and the equality of justice requires that a man should himself suffer whatever harm he has intended to be inflicted on another, according to Ex 21,24, "Eye for eye, tooth for tooth." Consequently it is just that he who by accusing a man has put him in danger of being punished severely, should himself suffer a like punishment.

Reply to Objection: 1. As the Philosopher says (Ethic. v, 5) justice does not always require counterpassion, because it matters considerably whether a man injures another voluntarily or not. Voluntary injury deserves punishment, involuntary deserves forgiveness. Hence when the judge becomes aware that a man has made a false accusation, not with a mind to do harm, but involuntarily through ignorance or a just error, he does not impose the punishment of retaliation.
2. He who accuses wrongfully sins both against the person of the accused and against the commonwealth; wherefore he is punished on both counts. This is the meaning of what is written (Dt 19,18-20): "And when after most diligent inquisition, they shall find that the false witness hath told a lie against his brother: then shall render to him as he meant to do to his brother," and this refers to the injury done to the person: and afterwards, referring to the injury done to the commonwealth, the text continues: "And thou shalt take away the evil out of the midst of thee, that others hearing may fear, and may not dare to do such things." Specially, however, does he injure the person of the accused, if he accuse him falsely. Wherefore the accused, if innocent, may condone the injury done to himself, particularly if the accusation were made not calumniously but out of levity of mind. But if the accuser desist from accusing an innocent man, through collusion with the latter's adversary, he inflicts an injury on the commonwealth: and this cannot be condoned by the accused, although it can be remitted by the sovereign, who has charge of the commonwealth.
3. The accuser deserves the punishment of retaliation in compensation for the harm he attempts to inflict on his neighbor: but the punishment of disgrace is due to him for his wickedness in accusing another man calumniously. Sometimes the sovereign remits the punishment, and not the disgrace, and sometimes he removes the disgrace also: wherefore the Pope also can remove this disgrace. When Pope Gelasius says: "We cannot remove the disgrace," he may mean either the disgrace attaching to the deed [infamia facti], or that sometimes it is not expedient to remove it, or again he may be referring to the disgrace inflicted by the civil judge, as Gratian states (Callist. I, Epist. ad omn. Gall. episc.).


We must now consider those sins which are committed against justice on the part of the defendant. Under this head there are four points of inquiry:

(1) Whether it is a mortal sin to deny the truth which would lead to one's condemnation?

(2) Whether it is lawful to defend oneself with calumnies?

(3) Whether it is lawful to escape condemnation by appealing?

(4) Whether it is lawful for one who has been condemned to defend himself by violence if he be able to do so?

Whether one can, without a mortal sin, deny the truth which would lead to one's condemnation?

Objection: 1. It would seem one can, without a mortal sin, deny the truth which would lead to one's condemnation. For Chrysostom says (Hom. xxxi super Ep ad Heb.): "I do not say that you should lay bare your guilt publicly, nor accuse yourself before others." Now if the accused were to confess the truth in court, he would lay bare his guilt and be his own accuser. Therefore he is not bound to tell the truth: and so he does not sin mortally if he tell a lie in court.
2. Further, just as it is an officious lie when one tells a lie in order to rescue another man from death, so is it an officious lie when one tells a lie in order to free oneself from death, since one is more bound towards oneself than towards another. Now an officious lie is considered not a mortal but a venial sin. Therefore if the accused denies the truth in court, in order to escape death, he does not sin mortally.
3. Further, every mortal sin is contrary to charity, as stated above (Question [24], Article [12]). But that the accused lie by denying himself to be guilty of the crime laid to his charge is not contrary to charity, neither as regards the love we owe God, nor as to the love due to our neighbor. Therefore such a lie is not a mortal sin.

On the contrary Whatever is opposed to the glory of God is a mortal sin, because we are bound by precept to "do all to the glory of God" (1Co 10,31). Now it is to the glory of God that the accused confess that which is alleged against him, as appears from the words of Josue to Achan, "My son, give glory to the Lord God of Israel, and confess and tell me what thou hast done, hide it not" (Jos 7,19). Therefore it is a mortal sin to lie in order to cover one's guilt.
I answer that Whoever acts against the due order of justice, sins mortally, as stated above (Question [59], Article [4]). Now it belongs to the order of justice that a man should obey his superior in those matters to which the rights of his authority extend. Again, the judge, as stated above (Question [67], Article [1]), is the superior in relation to the person whom he judges. Therefore the accused is in duty bound to tell the judge the truth which the latter exacts from him according to the form of law. Hence if he refuse to tell the truth which he is under obligation to tell, or if he mendaciously deny it, he sins mortally. If, on the other hand, the judge asks of him that which he cannot ask in accordance with the order of justice, the accused is not bound to satisfy him, and he may lawfully escape by appealing or otherwise: but it is not lawful for him to lie.

Reply to Objection: 1. When a man is examined by the judge according to the order of justice, he does not lay bare his own guilt, but his guilt is unmasked by another, since the obligation of answering is imposed on him by one whom he is bound to obey.
2. To lie, with injury to another person, in order to rescue a man from death is not a purely officious lie, for it has an admixture of the pernicious lie: and when a man lies in court in order to exculpate himself, he does an injury to one whom he is bound to obey, since he refuses him his due, namely an avowal of the truth.
3. He who lies in court by denying his guilt, acts both against the love of God to whom judgment belongs, and against the love of his neighbor, and this not only as regards the judge, to whom he refuses his due, but also as regards his accuser, who is punished if he fail to prove his accusation. Hence it is written (Ps 140,4): "Incline not my heart to evil words, to make excuses in sins": on which words a gloss says: "Shameless men are wont by lying to deny their guilt when they have been found out." And Gregory in expounding Jb 31,33, "If as a man I have hid my sin," says (Moral. xxii, 15): "It is a common vice of mankind to sin in secret, by lying to hide the sin that has been committed, and when convicted to aggravate the sin by defending oneself."

Whether it is lawful for the accused to defend himself with calumnies?

Objection: 1. It would seem lawful for the accused to defend himself with calumnies. Because, according to civil law (Cod. II, iv, De transact. 18), when a man is on trial for his life it is lawful for him to bribe his adversary. Now this is done chiefly by defending oneself with calumnies. Therefore the accused who is on trial for his life does not sin if he defend himself with calumnies.
2. Further, an accuser who is guilty of collusion with the accused, is punishable by law (Decret. II, qu. iii, can. Si quem poenit.). Yet no punishment is imposed on the accused for collusion with the accuser. Therefore it would seem lawful for the accused to defend himself with calumnies.
3. Further, it is written (Pr 14,16): "A wise man feareth and declineth from evil, the fool leapeth over and is confident." Now what is done wisely is no sin. Therefore no matter how a man declines from evil, he does not sin.

On the contrary In criminal cases an oath has to be taken against calumnious allegations (Extra, De juramento calumniae, cap. Inhaerentes): and this would not be the case if it were lawful to defend oneself with calumnies. Therefore it is not lawful for the accused to defend himself with calumnies.
I answer that It is one thing to withhold the truth, and another to utter a falsehood. The former is lawful sometimes, for a man is not bound to divulge all truth, but only such as the judge can and must require of him according to the order of justice; as, for instance, when the accused is already disgraced through the commission of some crime, or certain indications of his guilt have already been discovered, or again when his guilt is already more or less proven. On the other hand it is never lawful to make a false declaration.As regards what he may do lawfully, a man can employ either lawful means, and such as are adapted to the end in view, which belongs to prudence; or he can use unlawful means, unsuitable to the proposed end, and this belongs to craftiness, which is exercised by fraud and guile, as shown above (Question [55], Articles [3], seqq.). His conduct in the former case is praiseworthy, in the latter sinful. Accordingly it is lawful for the accused to defend himself by withholding the truth that he is not bound to avow, by suitable means, for instance by not answering such questions as he is not bound to answer. This is not to defend himself with calumnies, but to escape prudently. But it is unlawful for him, either to utter a falsehood, or to withhold a truth that he is bound to avow, or to employ guile or fraud, because fraud and guile have the force of a lie, and so to use them would be to defend oneself with calumnies.

Reply to Objection: 1. Human laws leave many things unpunished, which according to the Divine judgment are sins, as, for example, simple fornication; because human law does not exact perfect virtue from man, for such virtue belongs to few and cannot be found in so great a number of people as human law has to direct. That a man is sometimes unwilling to commit a sin in order to escape from the death of the body, the danger of which threatens the accused who is on trial for his life, is an act of perfect virtue, since "death is the most fearful of all temporal things" (Ethic. iii, 6). Wherefore if the accused, who is on trial for his life, bribes his adversary, he sins indeed by inducing him to do what is unlawful, yet the civil law does not punish this sin, and in this sense it is said to be lawful.
2. If the accuser is guilty of collusion with the accused and the latter is guilty, he incurs punishment, and so it is evident that he sins. Wherefore, since it is a sin to induce a man to sin, or to take part in a sin in any way---for the Apostle says (Rm 1,32), that "they . . . are worthy of death . . . that consent" to those who sin---it is evident that the accused also sins if he is guilty of collusion with his adversary. Nevertheless according to human laws no punishment is inflicted on him, for the reason given above.
3. The wise man hides himself not by slandering others but by exercising prudence.

Whether it is lawful for the accused to escape judgment by appealing?

Objection: 1. It would seem unlawful for the accused to escape judgment by appealing. The Apostle says (Rm 13,1): "Let every soul be subject to the higher powers." Now the accused by appealing refuses to be subject to a higher power, viz. the judge. Therefore he commits a sin.
2. Further, ordinary authority is more binding than that which we choose for ourselves. Now according to the Decretals (II, qu. vi, cap. A judicibus) it is unlawful to appeal from the judges chosen by common consent. Much less therefore is it lawful to appeal from ordinary judges.
3. Further, whatever is lawful once is always lawful. But it is not lawful to appeal after the tenth day [*Can. Anteriorum, caus. ii, qu. 6], nor a third time on the same point [*Can. Si autem, caus. ii, qu. 6]. Therefore it would seem that an appeal is unlawful in itself.

On the contrary Paul appealed to Caesar (Ac 25).
I answer that There are two motives for which a man appeals. First through confidence in the justice of his cause, seeing that he is unjustly oppressed by the judge, and then it is lawful for him to appeal, because this is a prudent means of escape. Hence it is laid down (Decret. II, qu. vi, can. Omnis oppressus): "All those who are oppressed are free, if they so wish, to appeal to the judgment of the priests, and no man may stand in their way." Secondly, a man appeals in order to cause a delay, lest a just sentence be pronounced against him. This is to defend oneself calumniously, and is unlawful as stated above (Article [2]). For he inflicts an injury both on the judge, whom he hinders in the exercise of his office, and on his adversary, whose justice he disturbs as far as he is able. Hence it is laid down (II, qu. vi, can. Omnino puniendus): "Without doubt a man should be punished if his appeal be declared unjust."

Reply to Objection: 1. A man should submit to the lower authority in so far as the latter observes the order of the higher authority. If the lower authority departs from the order of the higher, we ought not to submit to it, for instance "if the proconsul order one thing and the emperor another," according to a gloss on Rm 13,2. Now when a judge oppresses anyone unjustly, in this respect he departs from the order of the higher authority, whereby he is obliged to judge justly. Hence it is lawful for a man who is oppressed unjustly, to have recourse to the authority of the higher power, by appealing either before or after sentence has been pronounced. And since it is to be presumed that there is no rectitude where true faith is lacking, it is unlawful for a Catholic to appeal to an unbelieving judge, according to Decretals II, qu. vi, can. Catholicus: "The Catholic who appeals to the decision of a judge of another faith shall be excommunicated, whether his case be just or unjust." Hence the Apostle also rebuked those who went to law before unbelievers (1Co 6,6).
2. It is due to a man's own fault or neglect that, of his own accord, he submits to the judgment of one in whose justice he has no confidence. Moreover it would seem to point to levity of mind for a man not to abide by what he has once approved of. Hence it is with reason that the law refuses us the faculty of appealing from the decision of judges of our own choice, who have no power save by virtue of the consent of the litigants. On the other hand the authority of an ordinary judge depends, not on the consent of those who are subject to his judgment, but on the authority of the king or prince who appointed him. Hence, as a remedy against his unjust oppression, the law allows one to have recourse to appeal, so that even if the judge be at the same time ordinary and chosen by the litigants, it is lawful to appeal from his decision, since seemingly his ordinary authority occasioned his being chosen as arbitrator. Nor is it to be imputed as a fault to the man who consented to his being arbitrator, without adverting to the fact that he was appointed ordinary judge by the prince.
3. The equity of the law so guards the interests of the one party that the other is not oppressed. Thus it allows ten days for appeal to be made, this being considered sufficient time for deliberating on the expediency of an appeal. If on the other hand there were no fixed time limit for appealing, the certainty of judgment would ever be in suspense, so that the other party would suffer an injury. The reason why it is not allowed to appeal a third time on the same point, is that it is not probable that the judges would fail to judge justly so many times.

Whether a man who is condemned to death may lawfully defend himself if he can?

Objection: 1. It would seem that a man who is condemned to death may lawfully defend himself if he can. For it is always lawful to do that to which nature inclines us, as being of natural right, so to speak. Now, to resist corruption is an inclination of nature not only in men and animals but also in things devoid of sense. Therefore if he can do so, the accused, after condemnation, may lawfully resist being put to death.
2. Further, just as a man, by resistance, escapes the death to which he has been condemned, so does he by flight. Now it is lawful seemingly to escape death by flight, according to Si 9,18, "Keep thee far from the man that hath power to kill [and not to quicken]" [*The words in the brackets are not in the Vulgate]. Therefore it is also lawful for the accused to resist.
3. Further, it is written (Pr 24,11): "Deliver them that are led to death: and those that are drawn to death forbear not to deliver." Now a man is under greater obligation to himself than to another. Therefore it is lawful for a condemned man to defend himself from being put to death.

On the contrary The Apostle says (Rm 13,2): "He that resisteth the power, resisteth the ordinance of God: and they that resist, purchase to themselves damnation." Now a condemned man, by defending himself, resists the power in the point of its being ordained by God "for the punishment of evil-doers, and for the praise of the good" [*1P 2,14]. Therefore he sins in defending himself.
I answer that A man may be condemned to death in two ways. First justly, and then it is not lawful for the condemned to defend himself, because it is lawful for the judge to combat his resistance by force, so that on his part the fight is unjust, and consequently without any doubt he sins.Secondly a man is condemned unjustly: and such a sentence is like the violence of robbers, according to Ez 22,21, "Her princes in the midst of her are like wolves ravening the prey to shed blood." Wherefore even as it is lawful to resist robbers, so is it lawful, in a like case, to resist wicked princes; except perhaps in order to avoid scandal, whence some grave disturbance might be feared to arise.

Reply to Objection: 1. Reason was given to man that he might ensue those things to which his nature inclines, not in all cases, but in accordance with the order of reason. Hence not all self-defense is lawful, but only such as is accomplished with due moderation.
2. When a man is condemned to death, he has not to kill himself, but to suffer death: wherefore he is not bound to do anything from which death would result, such as to stay in the place whence he would be led to execution. But he may not resist those who lead him to death, in order that he may not suffer what is just for him to suffer. Even so, if a man were condemned to die of hunger, he does not sin if he partakes of food brought to him secretly, because to refrain from taking it would be to kill himself.
3. This saying of the wise man does not direct that one should deliver a man from death in opposition to the order of justice: wherefore neither should a man deliver himself from death by resisting against justice.


We must now consider injustice with regard to the person of the witness. Under this head there are four points of inquiry:

(1) Whether a man is bound to give evidence?

(2) Whether the evidence of two or three witnesses suffices?

(3) Whether a man's evidence may be rejected without any fault on his part?

(4) Whether it is a mortal sin to bear false witness?

Whether a man is bound to give evidence?

Objection: 1. It would seem that a man is not bound to give evidence. Augustine say (Questions. Gn 1,26) [*Cf. Contra Faust. xxii, 33,34], that when Abraham said of his wife (Gn 20,2), "She is my sister," he wished the truth to be concealed and not a lie be told. Now, by hiding the truth a man abstains from giving evidence. Therefore a man is not bound to give evidence.
2. Further, no man is bound to act deceitfully. Now it is written (Pr 11,13): "He that walketh deceitfully revealeth secrets, but he that is faithful concealeth the thing committed to him by his friend." Therefore a man is not always bound to give evidence, especially on matters committed to him as a secret by a friend.
3. Further, clerics and priests, more than others, are bound to those things that are necessary for salvation. Yet clerics and priests are forbidden to give evidence when a man is on trial for his life. Therefore it is not necessary for salvation to give evidence.

On the contrary Augustine [*Can. Quisquis, caus. xi, qu. 3, cap. Falsidicus; cf. Isidore, Sentent. iii, 55] says: "Both he who conceals the truth and he who tells a lie are guilty, the former because he is unwilling to do good, the latter because he desires to hurt."
I answer that We must make a distinction in the matter of giving evidence: because sometimes a certain man's evidence is necessary, and sometimes not. If the necessary evidence is that of a man subject to a superior whom, in matters pertaining to justice, he is bound to obey, without doubt he is bound to give evidence on those points which are required of him in accordance with the order of justice, for instance on manifest things or when ill-report has preceded. If however he is required to give evidence on other points, for instance secret matters, and those of which no ill-report has preceded, he is not bound to give evidence. On the other hand, if his evidence be required by authority of a superior whom he is bound to obey, we must make a distinction: because if his evidence is required in order to deliver a man from an unjust death or any other penalty, or from false defamation, or some loss, in such cases he is bound to give evidence. Even if his evidence is not demanded, he is bound to do what he can to declare the truth to someone who may profit thereby. For it is written (Ps 81,4): "Rescue the poor, and deliver the needy from the hand of the sinner"; and (Pr 24,11): "Deliver them that are led to death"; and (Rm 1,32): "They are worthy of death, not only they that do them, but they also that consent to them that do them," on which words a gloss says: "To be silent when one can disprove is to consent." In matters pertaining to a man's condemnation, one is not bound to give evidence, except when one is constrained by a superior in accordance with the order of justice; since if the truth of such a matter be concealed, no particular injury is inflicted on anyone. Or, if some danger threatens the accuser, it matters not since he risked the danger of his own accord: whereas it is different with the accused, who incurs the danger against his will.

Reply to Objection: 1. Augustine is speaking of concealment of the truth in a case when a man is not compelled by his superior's authority to declare the truth, and when such concealment is not specially injurious to any person.
2. A man should by no means give evidence on matters secretly committed to him in confession, because he knows such things, not as man but as God's minister: and the sacrament is more binding than any human precept. But as regards matters committed to man in some other way under secrecy, we must make a distinction. Sometimes they are of such a nature that one is bound to make them known as soon as they come to our knowledge, for instance if they conduce to the spiritual or corporal corruption of the community, or to some grave personal injury, in short any like matter that a man is bound to make known either by giving evidence or by denouncing it. Against such a duty a man cannot be obliged to act on the plea that the matter is committed to him under secrecy, for he would break the faith he owes to another. On the other hand sometimes they are such as one is not bound to make known, so that one may be under obligation not to do so on account of their being committed to one under secrecy. In such a case one is by no means bound to make them known, even if the superior should command; because to keep faith is of natural right, and a man cannot be commanded to do what is contrary to natural right.
3. It is unbecoming for ministers of the altar to slay a man or to cooperate in his slaying, as stated above (Question [64], Article [4]); hence according to the order of justice they cannot be compelled to give evidence when a man is on trial for his life.

Summa Th. II-II EN Qu.68 a.2