Section 155 of The Indian Evidence Act, 1872
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:
(1) by the evidence of persons who testify that they, from their knowledge of the witness, believe him to be unworthy of credit;
(2) by proof that the witness has been bribed, or has 1 accepted the offer of bride, or has received any other corrupt inducement to give his evidence;
(3) by proof of former statements inconsistent with any part of his evidence which is liable to be contradicted;
2
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 indicted for 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 the wound was not given by A or in his presence.
The evidence is admissible.