What is the test for denying a witness's privilege?

'(I)f the witness, upon interposing his claim, were required to prove the hazard in the sense in which a claim is usually required to be established in court, he would be compelled to surrender the very protection which the privilege is designed to guarantee. To sustain the privilege, it need only be evident from the implications of the question, in the setting in which it is asked, that a responsive answer to the question or an explanation of why it cannot be answered Might be dangerous because injurious disclosure Could result.' (Hoffman v. United States (1951) 341 U.S. 479, 486--487, 71 S.Ct. 814, 818, 95 L.Ed. 1118; emphasis added.)