§ 174 The Valuation of Evidence
The law of evidence comprises two parts. The first of these consists of rules for the measurement or determination of the probative force of evidence. The second consists of rules determining the modes and conditions of the production of evidence. The first deals with the effect of evidence when produced, the second with the manner in which it is to be produced. The first is concerned with evidence in all its forms, whether judicial or extrajudicial; the second is concerned with judicial evidence alone. The two departments are intimately connected, for it is impossible to formulate rules for the production of evidence without reference and relation to the effect of it when produced. Nevertheless the two are distinct in theory, and for the most part distinguishable in practice. We shall deal with them in their order.
In judicial proceedings, as elsewhere, the accurate measurement of the evidential value of facts is a condition of the discovery of truth. Except in the administration of justice, however, this task is left to common sense and personal discretion. Rules and maxims, when recognised at all, are recognised as proper for the guidance of individual judgment, not for the exclusion of it. But in this, as in every other part of judicial procedure, law has been generated, and, in so far as it extends, has made the estimation of probative force or the weighing of evidence a matter of inflexible rules excluding judicial discretion. These rules constitute the first and most characteristic portion of the law of evidence. They may be conveniently divided into five classes, declaring respectively that certain facts amount to:—
1. Conclusive proof—in other words, raise a conclusive presumption;
2. Presumptive proof—in other words, raise a conditional or rebuttable presumption;
3. Insufficient evidence—that is to say, do not amount to proof, and raise no presumption, conclusive or conditional;
4. Exclusive evidence—that is to say, are the only facts which in respect of the matter in issue possess any probative force at all;
5. No evidence—that is to say, are destitute of evidential value.
I. Conclusive presumptions.—By conclusive proof is meant a fact possessing probative force of such strength as not to admit of effective contradiction. In other words, this fact amounts to proof irrespective of the existence or non-existence of any other facts whatsoever which may possess probative force in the contrary direction. By a conclusive presumption is meant the acceptance or recognition of a fact by the law as conclusive proof.
Presumptive or conditional proof, on the other hand, is a fact which amounts to proof, only so long as there exists no other fact amounting to disproof. It is a provisional proof, valid until overthrown by contrary proof. A conditional or rebuttable presumption is the acceptance of a fact by the law as conditional proof.476
One of the most singular features in early systems of procedure is the extent to which the process of proof is dominated by conclusive presumptions. The chief part of the early law of evidence consists of rules determining the species of proof which is necessary and sufficient in different cases, and allotting the benefit or burden of such proof between the parties. He who would establish his case must maintain it, for example, by success in that judicial battle the issue of which was held to be the judgment of Heaven (judicium Dei); or he must go unscathed through the ordeal, and so make manifest his truth or innocence; or he must procure twelve men to swear in set form that they believe his testimony to be true; or it may be sufficient if he himself makes solemn oath that his cause is just. If he succeeds in performing the conditions so laid upon him, he will have judgment; if he fails even in the slightest point, he is defeated. His task is to satisfy the requirements of the law, not to convince the court of the truth of his case. What the court thinks of the matter is nothing to the point. The whole procedure seems designed to take away from the tribunals the responsibility of investigating the truth, and to cast this burden upon providence or fate. Only gradually and reluctantly did our law attain to the conclusion that there is no such royal road in the administration of justice, that the heavens are silent, that the battle goes to the strong, that oaths are naught, and that there is no just substitute for the laborious investigation of the truth of things at the mouths of parties and witnesses.
The days are long since past in which conclusive presumptions played any great part in the administration of justice. They have not, however, altogether lost their early importance. They are, indeed, almost necessarily more or less false, for it is seldom possible in the subject-matter of judicial procedure to lay down with truth a general principle that any one thing is conclusive proof of the existence of any other. Nevertheless such principles may be just and useful even though not wholly true. We have already seen how they are often merely the procedural equivalents of substantive rules which may have independent validity. They have also been of use in developing and modifying by way of legal fictions the narrow and perverted principles of the early law. As an illustration of their employment in modern law we may cite the maxim Res judicata pro veritate accipitur. A judgment is conclusive evidence as between the parties, and sometimes as against all the world, of the matters adjudicated upon. The courts of justice may make mistakes, but no one will be heard to say so. For their function is to terminate disputes, and their decisions must be accepted as final and beyond question.
II. Conditional presumptions.—The second class of rules for the determination of probative force are those which establish rebuttable presumptions. For example, a person shown not to have been heard of for seven years by those who would naturally have heard of him if he had been alive, is presumed to be dead. So also a negotiable instrument is presumed to have been given for value. So also a person accused of any offence is presumed to be innocent.
Many of these presumptions are based on no real estimate of probabilities, but are established for the purpose of placing the burden of proof upon the party who is best able to bear it, or who may most justly be made to bear it. Persons accused of crime are probably guilty, but the presumption of their innocence is in most cases and with certain limitations clearly expedient.
III. Insufficient evidence.—In the third place the law contains rules declaring that certain evidence is insufficient, that its probative force falls short of that required for proof, and that it is therefore not permissible for the courts to act upon it. An example is the rule that in certain kinds of treason the testimony of one witness is insufficient—almost the sole recognition by English law of the general principle, familiar in legal history, that two witnesses are necessary for proof.
IV. Exclusive evidence.—In the fourth place there is an important class of rules declaring certain facts to be exclusive evidence, none other being admissible. The execution of a document which requires attestation can be proved in no other way than by the testimony of an attesting witness, unless owing to death or some other circumstance his testimony is unavailable. A written contract can be proved in no other way than by the production of the writing itself, whenever its production is possible. Certain kinds of contracts, such as one for the sale of land, cannot be proved except by writing, no verbal testimony being of virtue enough in the law to establish the existence of them.
It is only in respect of very special kinds of contracts that written evidence can wisely be demanded by the law. In the case of all ordinary mercantile agreements such a requirement does more harm than good; and the law would do well in accepting the principle that a man’s word is as good as his bond. The Statute of Frauds, by which most of these rules of exclusive evidence have been established, is an instrument for the encouragement of frauds rather than for the suppression of them. How much longer is it to remain in force as a potent instrument for the perversion of English law? Its repeal would sweep away at one stroke the immense accumulation of irrational technicality and complexity that has grown in the course of centuries from this evil root.
V. Facts which are not evidence.—Fifthly and lastly there are rules declaring that certain facts are not evidence, that is to say, are destitute of any probative force at all. Such facts are not to be produced to the court, and if produced no weight is to be attributed to them, for no accumulation of them can amount to proof. For example, hearsay is no evidence, the bond of connexion between it and the principal fact so reported at second hand being in the eye of the law too slight for any reliance to be justly placed upon it. Similarly the general bad character of an accused person is no evidence that he is guilty of any particular offence charged against him; although his good character is evidence of his innocence.
These rules of exclusion or irrelevancy assume two distinct forms, characteristic respectively of the earlier and later periods in the development of the law. At the present day they are almost wholly rules for the exclusion of evidence; in earlier times they were rules for the exclusion of witnesses. The law imposed testimonial incapacity upon certain classes of persons on the ground of their antecedent incredibility. No party to a suit, no person possessing any pecuniary interest in the event of it, no person convicted of any infamous offence, was a competent witness. His testimony was deemed destitute of evidential value on account of the suspicious nature of its source. The law has now learned that it is not in this fashion that the truth is to be sought for and found. It has now more confidence in individual judgment and less in general rules. It no longer condemns witnesses unheard, but receives the testimony of all, placing the old grounds of exclusion at their proper level as reasons for suspicion but not for antecedent rejection. Whether rules for the exclusion of evidence are not in general exposed to the same objections that have already prevailed against the roles for the exclusion of witnesses is a question which we shall presently consider.