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 accepted the offer of a bribe, 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;
4. ***

Explanations
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

1. 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.
2. A is indicted for the murder of B.
   C says the 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.