What is the evidentiary test for denying electronic surveillance of a witness?

Id. at 944. See Gelbard v. United States, 408 U.S. 41, 71, 92 S.Ct. 2357, 2373, 33 L.Ed.2d 179 (1972) (White, J., concurring). ("Of course, where the Government officially denies the fact of electronic surveillance of the witness, the matter is at an end and the witness must answer.") The standard set out in Yanagita was fully complied with. The questions put to Archuleta were narrowly focused on specific criminal activity. It was thus relatively simple for the prosecutor to determine the evidentiary basis for the questions. In response to vague, sweeping charges of wiretapping, the government responded with specific, factual denials of illegal conduct. Gelbard requires no more. ⁵