In short: this is the informer’s privilege. An officer who comes to know of an offence cannot be forced to disclose whence — from whom or from where — the information came. The reason is practical: if sources could be named in court, few would ever come forward, and the flow of information about crime would dry up. The shield runs to a Magistrate or police officer for any offence, and to a revenue officer for offences against the public revenue — and the Explanation reads ‘revenue officer’ widely, covering any officer employed in or about the business of any branch of the public revenue. Two boundaries: it protects the source, not the information or the facts themselves; and it bars only compulsion — the officer is not obliged to name his informant. [OCR note: the source text read ‘when he got’; the section is ‘whence he got’ — the word means from where/whom, which is the whole point of the privilege.]

→ This carries forward IEA 1872 § 125 — the protection of the source of information about offences.