Can a witness invoke privilege to refuse to answer all relevant questions?

7 The only exception to this rule is the situation in which the trial court finds that the person claiming the privilege could " 'legitimately refuse to answer all relevant questions,' United States v. Gomez-Rojas, 507 F.2d 1213, 1220 (5th Cir.1975), because of the threat of incrimination from any relevant questioning...." (S.E.C. v. First Financial Group of Texas, Inc. (5th Cir.1981) 659 F.2d 660, 668-669.) In the absence of such a finding, a person cannot be totally excused from responding to relevant inquiries and may invoke the privilege only with respect to genuinely threatening questions. (Id.)