Neither the United States Code nor the Federal Rules of Evidence have a specific provision concerning the admissibility of polygraph examination results. In 1991, however, the President promulgated Military Rule of Evidence 707(a), which bars the admission of polygraph results, the opinion of the polygraph examiner, or any reference to an offer to take, failure to take, or taking of a polygraph examination in courts martial. Five years later, the United States Court of Appeals for the Armed Forces struck down the rule as an unconstitutional restriction on the defendant's right to present a defense in a case in which the defendant sought to corroborate his testimony with the results of a polygraph test administered by an investigative arm of the Air Force. United States v. Scheffer, 41 M.J. 683 (1996). The Solicitor General has filed a certiorari petition in the Supreme Court seeking review of the decision. United States v. Scheffer, No. 96-1133, petition for writ of certiorari filed January 16, 1997. If the petition is granted, the Supreme Court can be expected to decide the constitutional question during its 1997 Term. The Court's decision, if any, could affect the arguments that are available to federal prosecutors seeking to exclude polygraph results in the civilian courts.
For many years, the courts of appeals have upheld the exclusion of polygraph evidence on the ground that polygraphs are not "generally accepted" by the scientific evidence. Frye v. United States, 293 F. 1013 (D.C. Cir. 1923) (adopting "general acceptance" standard for admissibility of expert testimony based on scientific theory). P. Giannelli & E. Imwinkelried, Scientific Evidence 223-235 (2d ed. 1993) (noting that a majority of federal and state courts "follow the traditional rule, holding polygraph evidence inadmissible per se") (collecting authorities). In 1993, the Supreme Court held that, under Federal Rule of Evidence 702, expert testimony may not be excluded solely because it is based on scientific theory that has not yet achieved "general acceptance." Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993). Instead, the trial court must determine under Rule 702 "whether the expert is proposing to testify to (1) scientific knowledge that (2) will assist the trier of fact." 509 U.S. at 592. In determining whether the expert's testimony rests on scientific knowledge, the Supreme Court identified a non-exclusive list of several factors that the trial courts should consider: (1) whether the theory or technique can be and has been tested, (2) whether it has been subjected to peer review, (3) whether the technique has a high known or potential rate of error, and (4) whether the theory has attained general acceptance within the scientific community. Id. at 593-594.
Since Daubert, two circuits have retreated from the categorical position. United States v. Cordoba, 104 F.3d 225 (9th Cir. 1997); United States v. Posado, 57 F.3d 428 (5th Cir. 1995). In a pre-Daubert decision, United States v. Piccinonna, 885 F.2d 1529 (11th Cir. 1989) (en banc), the Eleventh Circuit held that polygraph results are admissible (1) when the parties stipulate to admissibility in advance of the test; or (2) when the polygraph results are used to impeach or corroborate the testimony of a witness. In the latter circumstance, the party seeking to introduce the polygraph results must provide adequate notice to the opposing party; the opposing party must be given adequate opportunity to have its own polygraph expert administer a test covering substantially the same questions; and the evidence must be admissible under the rules governing corroboration or impeachment.
Consequently, the government continues to have several good arguments for excluding polygraph evidence. First, a prosecutor can still attack the reliability of polygraph evidence both generally and as administered in the case at hand. The FBI polygraph unit has provided affidavits and live testimony in several district courts to rebut a defendant's proffer that his polygraph results are reliable, and stands ready to assist any prosecutor confronted with such a motion to introduce polygraph results.
Second, the prosecutor can argue that even if the test was properly administered and reliable, it would not "assist the trier of fact" under Rule 702. Jurors have long been considered competent to gauge the credibility of live witnesses without resort to expert opinion. Since time immemorial our system has entrusted credibility determinations to the judgment of juries, which assess credibility in reliance on their common-sense evaluations of demeanor, bias, and the plausibility of the narrative. Prosecutors should argue that expert opinion on credibility invades the jury's province.
Third, the prosecutor should argue that polygraph results are inadmissible under Rule 403 as prejudicial, misleading, and a waste of time. United States v. Williams, 95 F.3d 723, 729-30 (8th Cir. 1996) (polygraph results can mislead the jury); United States v. Pettigrew, 77 F.3d 1500, 1515 (5th Cir. 1996) (unilaterally obtained polygraphs examinations are almost never admissible under Rule 403); United States v. Sherlin, 67 F.3d 1208, 1216-17 (6th Cir. 1995) (Rule 403 is a proper ground for excluding polygraph results even after Daubert), cert. denied, 116 S. Ct. 795 (1996); United States v. Kwong, 69 F.3d 663, 668 (2d Cir. 1995) (polygraph questions were ambiguous and hence not probative of the central issues in the case), cert. denied, 116 S. Ct. 1343 (1996).
Finally, polygraph results may be inadmissible under Federal Rule of Evidence 608 "unless or until the credibility of that witness [is] first attacked." United States v. Piccinonna, 885 F.2d at 1536.
Although the government should seek the exclusion of polygraph results in the district court, there is no bar to the introduction of voluntary incriminatory statements made during a polygraph examination. If the defendant claims that his confession was coerced, some circuits have held that the government may rebut the claim of coercion by introducing evidence of the polygraph examination. United States v. Figueroa, 15 F.3d 706, 708 (7th Cir. 1995); United States v. Johnson, 816 F.2d 918, 1923 (3d Cir. 1987); United States v. Kampiles, 609 F.2d 1233, 1245 (7th Cir. 1979), cert. denied, 446 U.S. 954 (1980); Tyler v. United States, 193 F.2d 24, 31 (D.C. Cir.), cert. denied, 343 U.S. 908 (1952). Further, the Tenth Circuit has permitted the government to introduce polygraph results to explain why the government had not conducted a more thorough investigation. United States v. Hall, 805 F.2d 1410 (10th Cir. 1986).
Finally, in Wood v. Bartholomew, 116 S. Ct. 7 (1995), the Supreme Court held that because Washington state law does not permit the introduction of polygraph results at trial, the prosecutor did not violate his due process obligation under Brady v. Maryland, 373 U.S. 83 (1963), by failing to disclose that a government witness had failed a polygraph examination. "Disclosure of the polygraph results * * * could have had no direct effect on the outcome of trial, because [the defendant] could have made no mention of them either during argument or while questioning witnesses." 116 S. Ct. at 10. In other words, the inadmissible polygraph results were not "evidence," and therefore it was not "reasonably likely" that disclosure would have changed the outcome of the trial. Id. at 10. Because, however, many circuits no longer have a per se rule of exclusion regarding polygraph evidence, it is wiser in federal court to disclose unfavorable polygraph results of a testifying witness. United States v. Hart, 344 F. Supp. 522 (E.D.N.Y. 1971).