The credit of a witness may be impeached in the following ways by the adverse party, or, with the consent of the Court, by the party who calls him--
(a) by the evidence of persons who testify that they, from their knowledge of the witness, believe him to be unworthy of credit;
(b) by proof that the witness has been bribed, or has accepted the offer of a bribe, or has received any other corrupt inducement to give his evidence;
(c) by proof of former statements inconsistent with any part of his evidence which is liable to be contradicted.
Explanation.--A witness declaring another witness to be unworthy of credit may not, upon his examination-in-chief, give reasons for his belief, but he may be asked his reasons in cross-examination, and the answers which he gives cannot be contradicted, though, if they are false, he may afterwards be charged with giving false evidence.
Illustrations.
(a) A sues B for the price of goods sold and delivered to B. C says that he delivered the goods to B. Evidence is offered to show that, on a previous occasion, he said that he had not delivered goods to B. The evidence is admissible.
(b) A is accused of the murder of B. C says that B, when dying, declared that A had given B the wound of which he died. Evidence is offered to show that, on a previous occasion, C said that B, when dying, did not declare that A had given B the wound of which he died. The evidence is admissible