R v B (KG), [1993] 1 SCR 740, popularly known as the KGB case, is a leading Supreme Court of Canada decision on the admissibility of prior inconsistent statements as proof of the truth of their contents.

The issue before the Supreme Court of Canada was whether the recorded statements could be submitted as evidence to the truth of their contents under the principled exception to hearsay.

Lamer CJ adopted these two criteria in formulating the test for admitting prior inconsistent statements.

Third, "if the opposing party, whether the Crown or the defence, has a full opportunity to cross‑examine the witness at trial respecting the statement".

Lamer CJ also made clear that substitute reliability guarantors could be accepted in place of these strict guidelines, in certain cases.