Matter of the Enforcement of a Subpoena, 436 Mass. 784, 793-796 (2002), quoting Ward v. Peabody, 380 Mass. 805, 819 (1980). Grand juries "may not override constitutional rights, such as the right against self-incrimination ( Powers v. Commonwealth, 387 Mass. 563, 564-565), and may not issue unreasonable orders to produce documents ( Hale v. Henkel, 201 U.S. 43, 76)." Commonwealth v. Doe, 408 Mass. 764, 768 (1990).

This argument raises the question whether there are any limits on a grand jury's power to seek a court order obliging a person to appear involuntarily in a lineup. Although grand juries have broad authority to conduct inquiries ( Branzburg v. Hayes, 408 U.S. 665, 688 [1972]), they may not override constitutional rights, such as the right against self-incrimination ( Powers v. Commonwealth, 387 Mass. 563, 564-565 [1982]), and may not issue unreasonable orders to produce documents ( Hale v. Henkel, 201 U.S. 43, 76 [1906]). While John Doe's argument is expressed in constitutional terms, the standard that should guide a judge in passing on the lawfulness of an identification order need not be constitutionally based.

"[A] witness who asserts [the] privilege cannot be compelled to testify unless it is 'perfectly clear from a careful consideration of all the circumstances in the case, that the witness is mistaken, and that the answer[s] cannot possibly have such tendency' to incriminate."Powers v. Commonwealth, 387 Mass. 563, 564-565 (1982), quoting from Malloy v. Hogan, 378 U.S. 1, 12 (1964), and fromHoffman v. United States, 341 U.S. 479, 488 (1951).Commonwealth v. Martin, 423 Mass. 496, 502 (1996).Commonwealth v. McMiller, supra. Although not raised by either party, this analysis is irrelevant if Kibbe waived his privilege. In November, 1991, several months after the defendant was indicted, Kibbe told defense counsel about his drug use with the victim before the attack.

"[A] witness who asserts his privilege cannot be compelled to testify unless it is ` perfectly clear from a careful consideration of all the circumstances in the case, that the witness is mistaken, and that the answer[s] cannot possibly have such tendency' to incriminate" (emphasis original). Powers v. Commonwealth, 387 Mass. 563, 564-565 (1982), quoting from Malloy v. Hogan, 378 U.S. 1, 12 (1964), and Hoffman v. United States, 341 U.S. 479, 488 (1951). The Commonwealth argues that Solomont's assertion of her privilege was valid.

In determining whether a claim of privilege is justified, we apply Federal standards. Taylor v. Commonwealth, 369 Mass. 183, 187 (1975). Powers v. Commonwealth, 387 Mass. 563, 564-565 (1982). "Under these standards, a witness who asserts his privilege cannot be compelled to testify unless it is `" perfectly clear from a careful consideration of all the circumstances in the case that the witness is mistaken, and that the answer[s] cannot possibly have such tendency" to incriminate.'"

Represented by independent counsel, Mann claimed his privilege, which was allowed. The ruling was correct, if there was even slender ground for apprehending that testimony on the part of Mann might tend to incriminate him, see Powers v. Commonwealth, 387 Mass. 563, 564-565 (1982), and here the ground was solid. When the judge ruled, he knew the circumstances of the case.