The perjury trap is a form of entrapment defense, and thus must be affirmatively proven by the defendant. The defense is rarely proven, even though the claim is relatively common when grand jury testimony gives rise to perjury charges. See Gershman, The Perjury Trap, 129 U. Pa. L. Rev. 624 (1981). The defense requires that the defendant show the false answer was illegally procured by the government. Thus, when the grand jury is attempting to obtain useful information in furtherance of its investigation, the perjury trap doctrine does not apply. United States v. Brown, 49 F.3d 1162, 1168 (6th Cir. 1995), cert. denied, 116 S.Ct. 377 (1995); United States v. Chen, 933 F.2d 793, 797 (9th Cir. 1991).
PRACTICE TIP: The United States Supreme Court has ruled that there is also no duty to warn the witness of the consequences of committing perjury. United States v. Mandujano, 425 U.S. 564 (1976). Department guidelines, however, require prosecutors to give warnings resembling Miranda warnings to subjects or targets of grand jury investigations and to advise putative defendants of their status as such. See JM 9-11.151. When the defendant claims a perjury trap, those warnings demonstrate that the prosecutor did not call the witness to induce perjury, but rather to seek truthful testimony. United States v. Williams, 874 F.2d 968, 974-75 (5th Cir. 1989). Failure to give those warnings does not constitute grounds for dismissal of an indictment. United States v. Washington, 431 U.S. 181 (1977).
[cited in JM 9-69.200]