(4) when a man is prosecuted for rape or an attempt to ravish, it may be shown that the prosecutrix was of generally immoral character. 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.