Can a witness refuse to answer all relevant questions?

We have recognized a narrow exception to this general rule when the district court has sufficient knowledge of the case to conclude that "the witness could legitimately refuse to answer essentially all relevant questions." United States v. Tsui, 646 F.2d 365, 368 (9th Cir.1981) (internal quotations omitted), cert. denied, 455 U.S. 991 (1982). This is a very narrow exception. In order for it to apply, the court must be able to conclude that "any response to all possible questions ... would tend to incriminate the witness." Id. at 367 (internal quotations omitted). This conclusion must be based upon "some special or extensive knowledge of the case that allows the evaluation of the claimed Fifth Amendment privilege even in the absence of specific questions to the witness." United States v. Moore, 682 F.2d 853, 856 (9th Cir.1982) (Moore ).