A question frequently faced by Federal prosecutors is how to respond to an assertion by a prospective grand jury witness that if called to testify the witness will refuse to testify on Fifth Amendment grounds. If a "target" of the investigation and his or her attorney state in a writing, signed by both, that the "target" will refuse to testify on Fifth Amendment grounds, the witness ordinarily should be excused from testifying unless the grand jury and the United States Attorney agree to insist on the appearance. In determining the desirability of insisting on the appearance of such a person, consideration should be given to the factors which justified the subpoena in the first place, i.e., the importance of the testimony or other information sought, its unavailability from other sources, and the applicability of the Fifth Amendment privilege to the likely areas of inquiry.

Some argue that unless the prosecutor is prepared to seek an order pursuant to 18 U.S.C. § 6003, the witness should be excused from testifying. However, such a broad rule would be improper and make it too convenient for witnesses to avoid testifying truthfully to their knowledge of relevant facts. Moreover, once compelled to appear, the witness may be willing and able to answer some or all of the grand jury's questions without incriminating himself or herself.