dually choaked up Wells harbour, an engineer was permitted to prove from his own experiments, what were the effects of natural causes upon that particular harbour, and on other harbours similarly situated on the same coast, and that the removal of the bank would not, in his opinion, restore the harbour (1). So, where the question is, whether a seal has been forged, seal engravers may be called to shew a difference between a genuine impression and that supposed to be false. (2)

In cross-examinations, the object of which is to sift evidence, and try the credibility of the witnesses, a great latitude is allowed in the mode of putting questions. The rule, however, is still subject to certain limitations. A witness cannot be cross-examined as to any fact, which (if admitted) would be collateral, and wholly irrelevant to the matter in issue, for the purpose of contradicting him by other evidence, (in case he should deny the fact,) and in this manner to discredit his testimony (3); and if the witness answers such an irrelevant question before it is disallowed or withdrawn, evidence cannot afterwards be admitted to contradict his testimony on the collateral matter (4). In the application of this rule, the principal thing to be considered will be, whether the question is irrelevant to the points in issue between the parties. In an action for usury, it would be entirely immaterial and irrelevant to cross-examine the witness respecting other contracts supposed to have been made by the defendant, unless the witness had first said that the contracts were the same; and that was the point in the case of Spenceley v. De Willot. So it would be irrelevant to ask a witness in cross-examination, whether he had not attempted to dissuade another witness from attending the trial (5). But it is not irrelevant on the trial of a prisoner, to cross-exa

mine the witness to this point, whether, in consequence of being charged with robbing the prisoner, he had not said that he would be revenged upon him, &c.; and if the witness should deny having used such a threat, evidence may be given to contradict him. (1)

When a witness has been once sworn to give evidence, the other party may cross-examine him, though he gave no evidence for the party that called him (2). And it is reported to have been ruled at nisi prius, that, if a witness has been once examined by a party, the privilege of crossexamination continues in every stage of the cause; so, that the other party may call the same witness to prove his case, and in examining him may ask leading questions (3). In the case referred to, the witness might possibly have shewn a strong bias in favour of the first party that called him, and on this account perhaps a greater scope was granted to the adverse party than is usually allowed. It may happen, on the other hand, that the plaintiff calls a witness, unwillingly and from mere necessity, knowing him to be favourable to the other side: in such a case, to allow the defendant, on calling him up afterwards as his own witness, to put leading questions, would be giving him an unreasonable advantage; on the contrary, the Court might perhaps be induced to invest the plaintiff's counsel with some of the powers of cross-examination, at the same time that it would probably oblige the defendant's counsel to treat such a witness strictly as his own, and confine him within the limits of an examination in chief. If one party calls for the other party's books, but, when they are produced, declines using them, the mere calling for them will not make them evidence for the adverse party (4). It may, said Lord Kenyon, be matter of observation to the counsel on the other side, that the entries in the books

dually choaked up Wells harbour, an engineer was permitted to prove from his own experiments, what were the effects of natural causes upon that particular harbour, and on other harbours similarly situated on the same coast, and that the removal of the bank would not, in his opinion, restore the harbour (1). So, where the question is, whether a seal has been forged, seal engravers may be called to shew a difference between a genuine impression and that supposed to be false. (2)

In cross-examinations, the object of which is to sift evidence, and try the credibility of the witnesses, a great latitude is allowed in the mode of putting questions. The rule, however, is still subject to certain limitations. A witness cannot be cross-examined as to any fact, which (if admitted) would be collateral, and wholly irrelevant to the matter in issue, for the purpose of contradicting him by other evidence, (in case he should deny the fact,) and in this manner to discredit his testimony (3); and if the witness answers such an irrelevant question before it is disallowed or withdrawn, evidence cannot afterwards be admitted to contradict his testimony on the collateral matter (4). In the application of this rule, the principal thing to be considered will be, whether the question is irrelevant to the points in issue between the parties. In an action for usury, it would be entirely immaterial and irrelevant to cross-examine the witness respecting other contracts supposed to have been made by the defendant, unless the witness had first said that the contracts were the same; and that was the point in the case of Spenceley v. De Willot. So it would be irrelevant to ask a witness in cross-examination, whether he had not attempted to dissuade another witness from attending the trial (5). But it is not irrelevant on the trial of a prisoner, to cross-exa

(1) Folkes v. Chad, 1783, MS. cited by Buller J. in Goodtitle v. Braham, 4 T. R. 498.

(2) Per Ld. Mansfield in Folkes v. Chad, ib.

(3) Spenceley v. De Willot, 7 East, 108.

(4) Harris v. Tippet, 2 Campb. 638. (5) Harris v. Tippet, 2 Campb. 637.

mine the witness to this point, whether, in consequence of being charged with robbing the prisoner, he had not said that he would be revenged upon him, &c.; and if the witness should deny having used such a threat, evidence may be given to contradict him. (1)

When a witness has been once sworn to give evidence, the other party may cross-examine him, though he gave no evidence for the party that called him (2). And it is reported to have been ruled at nisi prius, that, if a witness has been once examined by a party, the privilege of crossexamination continues in every stage of the cause; so, that the other party may call the same witness to prove his case, and in examining him may ask leading questions (3). In the case referred to, the witness might possibly have shewn a strong bias in favour of the first party that called him, and on this account perhaps a greater scope was granted to the adverse party than is usually allowed. It may happen, on the other hand, that the plaintiff calls a witness, unwillingly and from mere necessity, knowing him to be favourable to the other side: in such a case, to allow the defendant, on calling him up afterwards as his own witness, to put leading questions, would be giving him an unreasonable advantage; on the contrary, the Court might perhaps be induced to invest the plaintiff's counsel with some of the powers of cross-examination, at the same time that it would probably oblige the defendant's counsel to treat such a witness strictly as his own, and confine him. within the limits of an examination in chief. If one party calls for the other party's books, but, when they are produced, declines using them, the mere calling for them will not make them evidence for the adverse party (4). It may, said Lord Kenyon, be matter of observation to the counsel on the other side, that the entries in the books

were in favour of his client, but cannot entitle him to offer the books in evidence to the jury. If, however, the party who has called for the books, inspects them, he thereby makes them evidence for the other party, although he has not used them himself in evidence (1). Where books are refused, it is a suspicious circumstance, and open to much observation, but it will not be conclusive against the party.

There are several ways of impeaching the credit of a witness. 1. The party, against whom a witness is called, may disprove the facts stated by him, or may examine other witnesses, as to his general character: but they will not be allowed to speak to particular facts or parts of his conduct (2); for, "though every man is supposed to be capable of supporting the one, it is not likely that he should be prepared to answer the other without notice;" and, even if he should happen to be prepared to defend himself, such evidence would generally afford a very slight and imperfect test of his credibility. The regular mode is, to inquire whether they have the means of knowing the former witness's general character, and whether from such knowledge, they would believe him on his oath (3). In answer to such evidence against character, the other party may cross-examine the witnesses as to their means of knowledge; or may attack their general character, and by fresh evidence support the character of his own witness. 2. The credit of a witness may be impeached, by proof that he has made statements out of court, on the same subject, contrary to what he swears at the trial (4). A letter, therefore, written by him, or a deposition signed by him, may be used as evidence to contradict his testimony; but a conviction before a magistrate, purporting to set out the

(1) Wharam v. Routlege, 5 Esp. N. P. C. 235.

(2) Bull. N. P. 296.

(3) Per Holt C. J. in Rockwood's

case, 4 St. Tr. 693. Mawson v. Hartsink, 4 Esp. N. P. C. 102.

(4) De Sailly v. Morgan, 2 Esp. N. P. C. 691.

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