Proof is the establishment of a disputed or controverted matter by lawful means or arguments. Proof is the result of evidence; evidence is the medium of proof. There is no proof without evidence, but there may be evidence without proof. Proof is judicial, if offered in court; otherwise it is extra-judicial. Proof is perfect, or complete, when it produces full conviction, and enables the judge without further investigation to pronounce sentence: imperfect, or incomplete, if it begets probability only. Canonists enumerate six kinds of perfect proof: the unshaken deposition of two witnesses, who are above all suspicion; a public document, or other instrument having the force of a public document, as, for instance, a certified copy of a public instrument; conclusive presumption of law; the decisive oath; judicial confession; evidence or notoriety of the fact. Imperfect or semi-proof is derived from the testimony of one witness only, or of several singular witnesses, or of two witnesses not entirely unshaken in their testimony or not beyond all suspicion; writings or instruments of a private character; a document admitted as authentic only on the strength of the handwriting; the necessary oath; presumption which is only probable, not conclusive; public report when legally proved. Two imperfect proofs cannot constitute perfect proof in criminal cases, in which proof must be clearer than the noonday sun; in matrimonial cases, when there is question of the validity of a marriage already contracted; or in civil actions of a grave character. With these exceptions two incomplete proofs tending to establish the same point may constitute full proof or conviction. Judicial proofs must as a rule be full and conclusive. There are, however, some exceptions. Thus the testimony of but one witness will suffice when it is beneficial to another person and hurts no one. Likewise in summary causes of little moment and not prejudicial to any one, half proof is sufficient; also when the judge is commissioned to proceed, having merely examined into the truth of the fact (sola facti veritate inspecta).
Confession, the acknowledgment by a person that what is charged or asserted by his opponent is true, is judicial or extra-judicial. Judicial confession is the best of proofs. It must be made in clear and definite terms, in court, that is, before the judge in his official capacity, during the trial, with certain knowledge of the fact and also of the consequences of said confession, by a person not under twenty-five years of age, acting with full liberty and not through fear. Such a confession makes further proof unnecessary; renders valid any previous defective proceedings; and, if made after the defendant has already been convicted, deprives him of the right of appeal. The confession may be revoked during the same session of court in which it was made; after an interruption the only remedy available is to show, if possible, that the confession was illegal, because wanting in some requisite quality, as above. Ordinarily a confession does not militate against accomplices or others, but only against the one confessing. Extrajudicial confession, if properly proved, constitutes in criminal causes a grave presumption, but not perfect proof; in civil cases it is sufficient for the pronouncing of sentence, if made in the presence of the plaintiff or his representative and if it specifically states the cause or origin of the obligation.
A public instrument is one drawn up by a public official with the required formalities. If a document be the work of a private person, or of an official who does not observe the prescribed formalities, it is a private instrument. Instruments to possess weight must be genuine and authentic. Public instruments consequently must bear the name, title, and seal of the official issuing them. Private documents should be written in the presence of witnesses and attested by them.
Circumstantial, presumptive, or indirect evidence, strong enough to establish a moral certainty, is admitted also in canon law, but it must be accepted with caution, and sentence modified in accordance with the degree of evidence. The rational basis of such evidence lies in the connexion of the facts or circumstances, known and proved, with the fact at issue. A presumption consequently is more or less strong, according as the fact presumed is a necessary (vehement, very strong presumption), or usual (strong presumption), or infrequent (rash, unreasonable presumption), consequence of the fact or facts seen, known, or proven. A presumption is legal, if the law itself draw the inference. This is of two kinds: rebuttable (juris simpliciter), which may be set aside by contrary proof; conclusive (juris et de jure), against which no direct proof is admitted. A presumption is natural (hominis) when the law permits the judge to draw whatever inference he considers warranted by the facts proved; such presumptions are sometimes called presumptions of facts. The general effect of presumption is to place the burden of proof on him against whom the presumption militates. A rash presumption is little more than mere suspicion; a grave or sound presumption constitutes imperfect proof, while a vehement presumption suffices in civil cases of not too great importance. Legal presumptions or presumptions of law are of course stronger than natural presumptions or presumptions of facts; while specific presumptions have more weight than those of a general character. Presumptions that favour the accused or the validity of an act already performed are preferred.
Oaths, as proof, are decisive (litis decisorium) or necessary. The decisive oath is given by the judge, when private interests are in question, to one of the litigants at the instance of the other. The case is decided in favour of the one taking the oath; if he refuse to swear, sentence is pronounced against him. The necessary oath is given by the judge on his own initiative, not at the request of one of the litigants, to complete imperfect proof, and is called supplementary; or to destroy the force of circumstantial evidence, arising especially from current rumour, against the accused, and is called purgative. This latter is permitted only when there is not at least semi-perfect proof. The supplementary oath is permissible only when there is at least imperfect and yet not full proof. It is not allowed in criminal actions or in important civil cases, as, for example, when the validity of a marriage or a religious profession is in question.
Witnesses testify as to the existence or non-existence, the origin, extent, and nature of a public report. Their testimony does not concern the truth or falsehood of the report. It is for the judge to trace the report to its source and accept it at its proper value. Since, however, it is to be presumed that public opinion is founded on fact, in civil matters it furnishes semi-perfect proof, when its existence is properly established. In criminal matters it has less weight still, being sufficient only for an investigation.
Evidence or notoriety of the fact, viz., when it is so open and evident that it cannot be concealed or denied, needs no proof. Hence a judicial inspection or visitation of the corpus delicti is often of advantage. Under this head might be mentioned the opinion of experts, who are appointed by the judge to examine certain matters and to give their expert testimony concerning the same.
Proof must be clear, specific, and in keeping with the charge or point at issue; otherwise confusion and obscurity will arise. To establish a point other than the one in question will avail nothing. Whether the evidence offered be relevant or not, the judge will determine. The issue must be established substantially, not necessarily in all its details. The burden of proof lies with the plaintiff, though the defendant must offer proof in support of his allegations, exceptions etc. What is evident needs no proof: in criminal cases this axiom applies only to what is evident in law, i.e. he who has the presumption of all in his favour is exempt from the necessity of proving his contention.
Judicial evidence must be introduced during the trial. Ordinarily, therefore, evidence may not be presented before the hearing of the petition or charge and the answer of the defendant to the same (contestatio litis). This rule, however, does not apply when the judge proceeds summarily or by inquiry; and likewise in certain cases where there is danger of the testimony being lost through death or other cause. Again, as a rule, no evidence will be admitted after the judge has closed the case. This general rule is not applied when the validity of a marriage is in question; in criminal cases, in which every opportunity of defence is given the accused; and occasionally in other trials, where further testimony is considered necessary or new evidence has been discovered.
Evidence must be presented to the judge or other person commissioned to receive it. It must be written down by the clerk in the acts or minutes of the trial: date of presentation of documents is noted on the documents themselves and attested by the signature of the clerk. Evidence in rebuttal, effected by witnesses, documents, or otherwise, must be admitted, the final word in criminal actions being given to the defendant.
It belongs to the judge to sift the depositions of witnesses or other proof and to determine the relative value of conflicting evidence. He must consider not merely the respective number of witnesses but their qualifications, intellectual and moral, their knowledge of the facts at issue, and so on. The stronger proof must prevail, and when proof is equally divided, the accused or possessor must be favoured, except in privileged cases (see EXAMINATION, Examination of Witnesses).
Decret. Greg. IX, l. II, tit. 18 sqq.; TAUNTON, Law of the Church, s.v. Proof; DROSTE-MESSMER, Canonical Procedure, etc., ii; SANTI, Prælectiones Juris Can., l. II, tit. 18 sqq.
APA citation. (1911). Proof. In The Catholic Encyclopedia. New York: Robert Appleton Company. http://www.newadvent.org/cathen/12454c.htm
MLA citation. "Proof." The Catholic Encyclopedia. Vol. 12. New York: Robert Appleton Company, 1911. <http://www.newadvent.org/cathen/12454c.htm>.
Transcription. This article was transcribed for New Advent by Douglas J. Potter. Dedicated to the Sacred Heart of Jesus Christ.
Ecclesiastical approbation. Nihil Obstat. June 1, 1911. Remy Lafort, S.T.D., Censor. Imprimatur. +John Cardinal Farley, Archbishop of New York.