Denman, C. J., permitted the latter to prove the contradictory statement. Wright v. Beckett, Lanc. Sum. Ass. 1833, 1 Moo. aud Ry. 414, S. C. The correctness of the ruling in the above case was afterwards argued before Lord Denman, C. J., and Bolland, B., sitting as judges of the Court of Common Pleas of Lancaster, when those learned judges differed and delivered their opinions at length. See 1 Moo. and R. 416. In accordance with the principle he laid down in the above case, Lord Denman has also held, that a party calling a witness who on cross-examination has given testimony unfavorable to him, may, on re-examination, ask the witness questions to show inducements to betray him. Dunn r. Aslett, 2 Moo. and R. 122. An opinion, adverse to the right of a party calling a witness to contradict him, by his own previous statement, has been expressed by a writer of great authority. Phill. Ev. 309, 7th ed. And this opinion seems to have been followed by other text writers. 2 Russ. 636. 2 Russ. 636. Mr. Phillipps, however, in the last edition *of his work, appears to have changed his [ *167] opinion, and observes, that in the administration of criminal justice more especially, the exclusion of the proof of contrary statements, might be attended with the worst consequences. Phill. Ev. 905, 8th ed.

Examination as to belief.] A witness can depose to such facts only as are within his own knowledge, but even in giving evidence in chief, there is no rule which requires a witness to depose to facts with an expression of certainty that excludes all doubt in his mind. It is the constant practice to receive in evidence a witness's belief of the identity of a person, or of the fact of a certain writing being the handwriting of a particular individual, though the witness will not aver positively to these facts. See Miller's case, 3 Wils. 427. It has been decided, that for false evidence so given, a witness may be indicted for perjury. Pedley's case, I Leach, 325; Phill. Ev. 898, 8th ed. (1).

Examination as to opinion.] Although, in general, a witness cannot be asked what his opinion upon a particular question is, since he is called for the purpose of speaking as to facts only, yet where matter of skill and judgment is involved, a person competent to give an opinion may be asked what that opinion is. Thus, an engineer may be called to say what, in his opinion, was the cause of an harbor being blocked up. Folkes v. Chad, 3 Dougl. 157 (a); Phill. Ev. 901, 8th ed.; 4 T. R. 498. S. C. cited. In a variety of other cases also, such evidence has been admitted. "Many nice questions," observes Lord Mansfield, " may arise as to forgery, and as to the impression of seals, whether the impression was made from the seal itself, or from an impression in wax. In such cases I cannot say that the opinion of seal-makers is not to be taken." Folkes v. Chad, 3 Dougl. 159 (b). So it seems is the opinion of any person in the habit of receiving letters, of the genuineness of a postmark. See Abbey v. Lill, 5 Bing. 299 (c). So the opinion of a ship-builder, on a question of sea-worthiness. Thornton v. Roy, Exch. Ass. Co. Peake, N. P. C. 25, 1 Campb. 117; Chapman v. Walton, 10 Bing. 57 (d) (2).

(1) A witness must not swear to impression simply. That is descending to a test too vague. It should be persuasion or belief founded on facts within his own knowledge. Carter v. Connell, 1 Whart. 392. Carmalt v. Post, 8 Watts, 406. Salmon v. Feinour, 6 Gill & J. 60. Jones v. Chiles, 2 Dana, 32.

(2) Rochester v. Chester, 3 N. Hamp. 349. Forbes v. Carothers & al., 3 Yeates, 527. Car(a) Eng. Com. L. Rep. xxvi. 63. (b) Id. (c) ld. xv. 452. (d) Id. xxv. 28.

66

In Campbell v. Rickards, 5 B. and Ad. 840 (a), in a case of insurance, it was held, (overruling several previous decisions) that the materiality of a fact concealed is a question for the jury alone. Witnesses conversant in a particular trade may be allowed to speak to a prevailing practice in that trade; scientific persons may give their opinions on matters of science; but witnesses are not receivable to state their views on matters of legal or moral obligation, nor on the manner in which others would probably be influenced, if the parties acted in one way rather than another."

It is the constant practice to examine medical men as to their judgment with regard to the cause of a person's death, who has suffered violence; and where, on a trial for murder, the defence was insanity, the judges to whom the point was referred, were all of opinion that in such a case a [*168] witness of medical skill might be asked *whether, in his judgment, such and such appearances were symptoms of insanity, and whether a long fast, followed by a draught of strong liquor, was likely to produce a paroxysm of that disorder in a person subject to it? Several of the judges doubted whether the witness could be asked his opinion on the very point which the jury were to decide, viz., whether from the other testimony given in the case, the act with which the prisoner was charged was, in his opinion, an act of insanity. Wright's case, Russ. and Ry. 456 (b). On an indictment for cutting and maiming, Park, J., on the authority of the above case, allowed a medical man, who had heard the trial, to be asked whether the facts and appearances proved showed symptoms of insanity. Searle's case, 1 Moo. and R. 75 (1).

A question may arise in these cases, whether, where a witness, a medical man, called to give his opinion as matter of skill, has made a report of the appearances or state of facts at the time, he may be allowed to read it as part of his evidence. The practice in Scotland on this point is as follows: The scientific witness is always directed to read his report, as affording the best evidence of the appearances he was called on to examine, yet he may be, and generally is, subjected to a further examination by the prosecutor, or to a cross-examination on the prisoner's part; and if he is called on to state any facts in the case, unconnected with his scientific report, as conversations with the deceased, confessions made to him by the prisoner, or the like, utitur jure communi, he stands in the situation of an ordinary witness, and can only refer to the memoranda to refresh his memory. Alison, Prac. Cr. Law of Scotland, 541.

Where, on an indictment for uttering a forged will, which, together with the writings in support of such will, it was suggested, had been written over pencil marks which had been rubbed out, Parke, B., (after consulting Tindal, C. J.,) held, that the evidence of an engraver who had examined the paper with a mirror, and traced the pencil marks, was admissible on the part of the prosecution, but that the weight of the evi

malt v. Post, 8 Watts, 406. Gentry. v. McMinnis, 3 Dana, 382. Bullock v. Wilson, 5 Porter, 338. Kellogg v. Krauser, 14 S. & R. 137. Morse v. The State, 6 Conn. 9. People v. De Graff, 1 Wheeler's C. C. 205..

(1) As to the evidence of experts generally, see Norman v. Wells, 17 Wend. 136. Cottril v. Myrick, 3 Fairfield, 222. Boies v. M'Allister, Ibid. 308. Lester v. Pittsford, 7 Verm. 158. Goodwin's case, 5 Rogers's Rec. 26. Where the opinion of an expert is offered, the Court may hear evidence first to ascertain whether he is an expert, and then allow the opinion to be given in evidence. Mendum's case, 6 Rand. 704. See 2 Starkie's Ev. New Ed. 932 n. 2 Russ. C. & M. 623.

(a) Eng. Com. L. Rep. xxvii. 207. (b) 1 Eng. C. C. 456.

dence would depend upon the way in which it would be confirmed. Williams's case, 8 C. and P. 434 (a).

In proving the laws of foreign countries also, the opinions of competent witnesses are admissible. The unwritten law of a foreign state may be proved by the parol evidence of witnesses possessing professional skill; but where the laws are in writing, a copy, properly authenticated, must be produced. Per Gibbs, C. J., Millar v. Heinrick, 4 Campb. 155; but see Boehtlinck v. Schneider, 3 Esp. 58. Thus on the trial of the Wakefields, for abduction, a gentleman of the Scotch bar was examined, as to whether the marriage, as proved by the witnesses, would be a valid marriage according to the law of Scotland. Wakefield's case, Murray's ed., p. 238. So it is laid down by a foreign writer of eminence, that foreign unwritten laws, customs, and usages, may be proved, and, indeed, must ordinarily be proved by parol evidence. The usual course is to make such proof by the testimony of competent witnesses, instructed in the law, under oath. Story's Com. on the Conflict of Laws, 530 (1).

*CREDIT OF WITNESSES-HOW IMPEACHED AND [ *169 ]

Credit of witnesses, how impeached-General rules.] The credit of a witness may be impeached, either simply by questions put to him on cross-examination, or by calling other witnesses to impeach his credit.

Questions with regard to particular facts tending to degrade the witness, and affect his character and credit, may be put to him on cross-examination, even though irrelevant to the matter in issue; but the party putting them must be satisfied with the answers given by the witness, and cannot call witnesses to prove those answers false.

Questions with regard to such particular facts may be put to a witness

(1) Talbot v. Seeman, 1 Cranch, 12, 38. Church v. Hubbert, 2 Id. 236. Strother v. Lucas, 6 Peters, 763. Consequa v. Willing & al., Peters's C. C. Rep. 225. Seton v. Delaware Ins. Co., 2 Wash. C. C. Rep. 175. Robinson v. Clifford, Id. 1. Hill v. Packard, 5 Wend. 375. 2 Íd. 411. Raynham v. Canton, 3 Pick. 293. Brackett v. Norton, 4 Conn. 517. Hempsted v. Reed, 6 Conn. 486. Tarlton v. Briscoe, 4 Bibb, 73. Talbot v. David, 2 Marsh. 609. Baptisti & al. v. Devolunbrun, 5 Har. & J. 86. Kenny v. Clarkson, 1 Johns. 385. Woodbridge v. Austin, 2 Tyler, 367. Frith v. Sprague, 14 Mass. 455. Smith v. Elder, 3 Johns. 145. Denison v. Hyde, 6 Conn. 508. Middlebury College v. Cheney, 1. Verm. 336. M'Rae v. Mattoon, 13 Pick. 53. Dyer v. Smith, 12 Conn. 384. Owen v. Boyle, 15 Maine, 147.

It lies on the party objecting to parol proof to show that the law is written. Dougherty v. Snyder, 15 S. & R. 87. Newsome v. Adams, 1 Louis. 153. Taylor v. Swell, 3 Id. 53. Livingston v. Maryland Ins. Co., 6 Cranch, 274.

(a) Eng. Com. L. Rep. xxxiv. 466.

on cross-examination, and if relevant to the matter in issue, and denied by the witness, other witnesses may be called by the cross-examining party to contradict him.

Where the witness himself is not cross-examined to impeach his credit, but other witnesses are called for that purpose, they cannot be examined as to particular facts, but only as to the witness's general character for veracity.

The party calling a witness will not on his giving evidence against him, be allowed to call witnesses to impeach his credit.

The cases decided upon these general rules will now be stated.

Credit impeached by irrelevant questions on cross-examination.] Although it is not allowable on cross-examination to put questions to a witness, not relating to the matter in issue, for the purpose, if he answers them against the cross-examining party, of contradicting him by other witnesses, yet it is a well established rule, that questions not relevant may be put to a witness for the purpose of trying his credibility; but in such case the party cross-examining must be satisfied with his answer. See Spenceley v. De Willott, ante, p. 156 (1). Thus where on a trial for sheep-stealing, the principal witness being the prisoner's apprentice, Lawrence, J., permitted him on cross-examination to be asked, whether he had not been charged with robbing his master, and whether he had not said that he would be revenged of him, and would soon fix him in gaol. The witness answering both questions in the negative, the prisoner's [ *170] counsel *then proposed to prove, that he had been charged with robbing his master, and had spoken the words imputed to him; but Lawrence, J. said, that his answer must be taken as to the former, but that as the words were material to the guilt or innocence of the prisoner, evidence might be adduced that they were spoken by the witness. Yewin's case, 2 Campb. 638 (n.) A witness was asked, whether he had not attempted to persuade a person called by the other side from attending to give his evidence, which he denied. It was proposed to call a witness to contradict him, but Lawrence, J., said, "Had this been a matter in issue, I would have allowed you to call witnesses to contradict, but it is entirely collateral, and you must take his answer. I will permit questions to be put to a witness, as to any improper conduct of which he may have been guilty, for the purpose of trying his credit; but when these questions are irrelevant to the issue on the record, you cannot call witnesses to contradict the answers. No witness can be prepared to support his character as to particular facts, and such inquiries would lead to endless confusion." Harris v. Tippett, 2 Campb. 637.

So where a witness to the character of a prisoner was cross-examined as to whether he had not said the prisoner should not be acquitted, if it cost him 201., and whether he had not endeavored to persuade some of the witnesses for the prosecution to forbear to give evidence, both of which he denied, Coleridge, J., held that evidence could not be called to contradict him. Lec's case, 2 Lewin, C. C. 154.

On the trial of Lord Stafford, proof was admitted on the part of the prisoner, that Dugdale, one of the witnesses for the prosecution, had en

(1) See Ante, p. 156, n. 1.

deavored to suborn witnesses to give false evidence against the prisoner. 7 How. St. Tr. 1400.

Credit impeached-by relevant questions-and contradiction by other witnesses.] Where a question tending to impeach the credit of the witness is not irrelevant to the issue, he may not only be compelled to answer it, but the other side may call witnesses for the express purpose of contradicting him, vide ante, p. 162. In an action against the defendant as the maker of a promissory note, which by his plea he denied having made, Coleridge, J., permitted a female servant of the plaintiff, who was one of the attesting witnesses to the note, to be asked in cross-examination, whether she did not constantly sleep with her master, and on her denying it, allowed a witness to be called to prove she did so. The learned judge observed, "The question is whether the witness had contracted such a relation with the plaintiff as might induce her the more readily to conspire with him to support a forgery, just in the same way as if she had been asked if she was the sister or daughter of the plaintiff, and had denied the fact." Thomas v. David, 7 C. and P. 350 (a).

So what was said or written by a witness at a previous time, may be given in evidence to contradict what he has said at the trial, if it relate to the matter in issue (1). De Sailly v. Morgan, *2 Esp. 691. [ *171 ] Thus, in a policy case, the captain's protest has been admitted in evidence to contradict what he has stated at the trial. Christian v. Combe, 2 Esp. 489.

On the question, what matter is receivable in evidence, what not receivable, for the purpose of contradicting a witness (by proof of contrary statements made by him) it is not possible to lay down any precise general rule. The evidence offered for that purpose, must relate to something, stated by the witness, not wholly irrelevant to the matters in issue. Phill. Ev. 938, 8th ed.

But in order to let in this evidence in contradiction, a ground must be laid for it, in the cross-examination of the witness who is to be contradicted. When a witness has been examined as to particular transactions, if the other side were permitted to give in evidence declarations made by him respecting those transactions at variance with his testimony, without first calling the attention of the witness to those declarations, and refreshing his memory with regard to them, it would, as it has been observed, have an unfair effect upon his credit. Accordingly, it is the practice of the courts to ask a witness, whether he has held such a conversation, or made such a declaration, and such previous question is considered a necessary foundation for the contradictory evidence of the declaration or conversation to be adduced on the other side, and if the party has neglected to lay this foundation, the court will in its discretion recall the witness for that purpose (2). The Queen's case, 2 Br. and Bingh. 301 (b).

(1) When one party calls in witness a paper, admitted by the witness to be true, although not then under oath, contradictory to his testimony, it is competent evidence for the other party. Robinson v. Heard, 15 Maine, 296. But a party cannot after examining a witness give in evidence his former testimony and declarations, ostensibly to discredit him, but in truth to operate as independent evidence. Smith e. Price, 8 Watts, 447.

(2) Evertson v. Carpenter, 17 Wend. 419. See also Tucker v. Welsh, 17 Mass. 160. Ware v. Ware, & Greenl. 42.

(a) Eng. Com. L. Rep. xxxii. 537. (b) Id. vi. 123.