mony. Lord Campbell, indeed, once said of experts, "They come with such a bias on their minds to support the cause in which they are embarked, that hardly any weight should be given to their evidence" (m). It is also deserving of remark, that there is no English case in which a witness has been indicted for perjury in a mere matter of opinion; nor does it seem that an indictment would lie, unless the opinion given amounts to the assertion of a fact that is untrue, or suggests an inference that is obviously false.

Books, and, in particular, dictionaries (n), are admissible to show the sense in which words are used; and especially in cases of libel defendants have been permitted to refer largely to previous publications, and to read them as part of their defence, in order to show that certain forms of expression were not meant as matter of reproach or ridicule; and to explain whether they have been used in a metaphorical or literal sense. Books also may be used to show the opinions of their writers on their subjects; but such opinions cannot be made evidence of specific facts. "Thus, it is not competent in an action for not farming according to covenant, to refer to books for the purpose of showing what is the best way of farming; nor in an action on the warranty of a horse would it be allowable to refer to works of a veterinary

(m) 10 C. & F. 191. See also the views of Jessel, M. R., as to expert evidence, in Lord Abinger v. Ashton, L. R., 17 Eq. 373; 22 W. R. 582.

(n) Clements v. Golding, 2 Camp. 25.

surgeon to show what is unsoundness" (o). So in an action for a libel charging the plaintiff with being a rebel and traitor, "because he was a Roman Catholic," the defendant was not allowed to justify by citing books of authority among the Roman Catholics, which seemed to show that their doctrines were inimical to loyalty (p). In all such cases, as also in the proof of foreign law, the evidence is matter of science, which must be given by experts or scientific witnesses in court. Books are only hearsay, often of the most vague, inconsistent, and remote character, statements made by absent, perhaps anonymous, witnesses, who write without being under the fear of the spiritual or secular penalties of an oath, and without being subject to cross-examination. It is plain, therefore, on the first principles of evidence, that they are without any of the elements of legal credibility.

The general rule will not be construed to exclude from the consideration of a jury anything which would assist them in making up their minds upon the facts in dispute, but is intended simply to prevent the functions of the jury being usurped by the witness, which would be done were he allowed to lead their opinion by his own.

(0) Per Pollock, C. B., Darby v. Ouseley, 1 H. & N. 12.
(p) Darby v. Ouseley, 1 H. & N. 1.

CHAPTER VII.

PRIVILEGE.

EXCEPT when some positive rule intervenes, a witness is compellable to answer any question that may be put to him. It is generally understood now, that a witness may be asked any question (except questions tending to show that he has been guilty of adultery); but there are many questions which he will not be compellable, and some which he will not be permitted, i. e. is not competent, to answer. So in documentary evidence every writing is admissible, except when it is excluded by a similar principle of law.

Wherever a witness is not compellable or not competent to answer any question, it is because some privilege intervenes, which privilege is sometimes that of the witness himself, sometimes that of another person, and sometimes that of the State, which asserts the right of excluding certain kind of evidence on grounds of public policy. Where the privilege is that of the witness himself, he may waive it and answer the question; where the privilege is that of another person, such person may waive it and permit the witness to answer, but the waiver cannot proceed from the witness himself. Where, in reliance on privilege, a witness refuses to answer, or is not allowed to answer any question, no presumption

arises that the evidence so withheld is unfavourable

to any person.

The different kinds of privilege will be gathered from the following rules, viz. :

RULE 1.

A witness is not compellable to answer any question or to produce any document tending to criminate him.

I. e. on the principle nemo tenetur seipsum prodere, a witness, whether a party to a suit or not, cannot be compelled to answer any question, whether put virâ voce or in the form of a written interrogatory (a), the answer to which may expose, or tend to expose, him to a criminal charge, penalty, or forfeiture of any kind. This rule is recognized and expressed by the Law of Evidence Amendment Act, 1851, which, after making the parties to civil actions and suits competent and compellable witnesses on behalf of either party, enacts that nothing in the act shall render any person compellable to answer any question tending to criminate himself or herself (b). This rule of protection is not confined to what may tend to subject a witness to penalties by the laws of England (c). On similar grounds the production of documents may be refused. That this is so is, it is submitted, beyond question in spite of the doubt

(a) Martin v. Treacher, L. R., 16 Q. B. D. 507; 55 L. J., Q. B. 209; 54 L. T. 7; 34 W. R. 315.

(b) 14 & 15 Vict. c. 99, s. 3.

(c) U. S. A. v. Macrae, L. R., 3 Ch. 79. But see King of Two Sicilies v. Wilcox, 1 Sim. N. S. 331.

supposed to be thrown upon it by the Court of Appeal in Webb v. East (d). If it were not so the decision of Lord Eldon in Parkhurst v. Lowten (e) would be erroneous, and the recent decision of the Court of Appeal in Redfern v. Redfern (f) would have been different to what it was. Besides which, there would then exist this abnormal state of things, that a man could be compelled to produce a written statement made by himself which would criminate him, but would be protected from being required to make the same statement orally.

The protection must always be claimed on oath, i. e. the party claiming it must pledge his oath that the answer to a question or the production of a document would tend to criminate him (g).

In R. v. Garbett (h), it was held that a witness is not compellable to answer a question if the court be of opinion that the answer might tend to criminate him. It was also held in the same case that the court may compel a witness to answer any such question; but that if the answer be subsequently used against the witness in a criminal proceeding, and a conviction obtained, judgment will be respited and the conviction reversed. In R. v. Boyes (i), Cockburn, C. J., in delivering the judgment of the court, said: "To entitle a party called as a witness

(d) L. R., 5 Ex. D. 108.

(e) 1 Merivale, 391.

(f) L. R. (1891), P. 139.
(g) See Webb v. East, ubi supra.

(h) 1 Den. 236.

(i) 1 B. & S. 311.