Is there any evidence that a witness at a grand jury has been subject to electronic surveillance?

We have recently confronted allegations by grand jury witnesses that their attorneys had been "subject to electronic surveillance by someone." In United States v. Fitch & Meisel, supra note 12, 472 F.2d 548, we upheld the district court's denial of their claim and apparent refusal to hold a hearing on the matter and noted that "the vague and speculative affidavit of counsel required no more" than the Government's affidavit denying monitoring of any conversations of counsel talking with the witnesses (id at 549).¹⁴