2001-2007 Peter Nordberg. E-mail: webmaster@daubertontheweb.com. Last revised: 9/17/06. See the reviews. Buy the T-shirt. Read the disclaimers. View the FAQ.


     "An appeal to truth is scarcely a prerogative of a society which
      dragoons its members to own up the better to hunt them down."

       -- Theodor Adorno, Minima Moralia

Polygraph Evidence

    In United States v. Scheffer, 523 U.S. 303 (1998), the Court was forced to deal, albeit indirectly, with Daubert's implications for the admissibility of polygraph evidence.  Polygraphy, of course, has long been widely and justly regarded as fraught with dubiety.  Indeed, so tenuous are polygraphy's claims to reliability that a rule of expert evidence failing to exclude polygraphy in definitive terms can fairly be regarded as "falsified," in the sense of failing to generate the plainly appropriate result.

Polygraphy Before and After Daubert

    For many years, it was commonly assumed that polygraphers had in fact been permanently banished from the courtroom by virtue of the holding in Frye v. United States, 54 App. D.C. 46, 293 F. 1013 (1923).  The court in Frye concluded that polygraph evidence was unacceptable for want of its general acceptance in the scientific community, and other courts subsequently reaching the question were happy, with near unanimity, to follow Frye's lead.  Not only, after all, did polygraphy's scientific pretensions seem shaky, but the polygraphers' approach to truth-seeking also differed radically from  jurisprudential ones.  Courts were generally quite content, therefore, to cite Frye and throw the polygraphy out.

    In Daubert, however, the Supreme Court rejected Frye's "general acceptance" test, and as a probably unintended consequence, the question of polygraph evidence was again open.  By 1997, numerous lower courts had interpreted Daubert, with varying degrees of trepidation, as potentially permitting the introduction of polygraph evidence in the sound discretion of the trial court.  Click here for illustrative decisions in this vein.

Scheffer Forces the Issue

     That Daubert should have spawned new evidentiary respectability for polygraphy was no doubt an intellectual embarrassment, and for a time the Supreme Court managed to avoid confronting it.  Its hand was arguably forced, however, when the United States Court of Appeals for the Armed Forces held that a special rule of evidence flatly barring all polygraph evidence in military proceedings (a rule promulgated by President and former CIA director George H.W. Bush) violated the right of the accused to present a defense under the Sixth Amendment.   Although ultimately resting on constitutional grounds, this renegade judicial opinion purported to draw support, as well, from the developing appellate polygraph jurisprudence under Daubert.

    It was bad enough, no doubt, to see Daubert so unapologetically trotted out in support of technological "lie detection."  But in fact matters were far worse than that.  The decision by the military's appellate tribunal in Scheffer, if valid, would tend to imply that all criminal defendants, not just armed forces personnel, enjoyed some sort of general right to introduce polygraph evidence, at least upon a proper foundation -- a right of constitutional proportions and therefore not amenable to statutory revocation, and one not enjoyed by prosecutors, for whom the Constitution displays no special solicitude.

    A writ of certiorari was perhaps inevitable in these circumstances.  Still, it cannot have made many people happy.  The members of the criminal defense bar, if taking the long view, cannot have been rooting for any Supreme Court decision that might, even potentially, help the polygrapher's nose into the tent -- or for a decision that would circumscribe Sixth Amendment rights as a way of keeping polygraphy out.  Nor was the Scheffer case an ideal vehicle for polygraphy's enthusiasts -- judicial deference to a rule of evidence never being stronger, perhaps, than when the rule has been propounded for the military by the Commander in Chief.  And the Supreme Court, having opened this particular Pandora's box by overruling Frye, was going to have some explaining to do.

The Supreme Court's Scheffer Opinion

    In the event, predictably enough, there were plenty of votes on the Rehnquist Court to nix any Sixth Amendment right to present a polygrapher's testimony in one's defense.  But just as predictably, the Court had difficulty explaining why, if polygraph testimony might be found scientifically "reliable" under Daubert, a criminal defendant could claim no constitutional right to present it.  According to the Court's main opinion, authored by Justice Thomas and joined in pertinent part by seven other Justices, the explanation goes something like this: (1) A jurisdiction may legitimately take steps rationally calculated to ensure that only reliable evidence is presented to the fact finder; (2) there is no consensus, among scientists or among courts, on whether polygraph evidence is reliable (a standard eerily reminiscent of Frye's "general acceptance" test); (3) a rational jurisdiction could conclude that polygraph evidence is sufficiently unreliable to warrant a universal, per se ban; and so (4) the President cannot be said to have acted irrationally in promulgating such a ban for military proceedings.

    All of this is reasonably persuasive, and also relatively lucid, until one delves more deeply into the Court's exegesis of proposition (3).  The absence of a consensus in polygraphy's favor, it then transpires, does not arise from the existence of valid arguments on both sides.  Rather, it flows from polygraphy's inability to satisfy the basic rational demands of empirical science.  Or, as the Court puts it, consensus is elusive because "there is simply no way to know in a particular case whether a polygraph examiner's conclusion is accurate, because certain doubts and uncertainties plague even the best polygraph exams."  (The emphasis is mine.)

    Now if polygraph evidence is ever to be admissible, this last quoted sentence could serve admirably as a limiting instruction.  On its face, however, a flat statement that polygraph exams are neither verifiable nor falsifiable in any particular instance would also seem to represent a powerful argument that polygraph evidence should never be admissible in the first place.  To be sure, the quoted sentence is open to a minimalist interpretation, under which Justice Thomas is simply expostulating in an epistemological vein and noting that no empirical hypothesis is apodictically certain.  But to buttress a holding that no serious Sixth Amendment interest is infringed by the exclusion of a criminal defendant's polygraph evidence, the quoted sentence has to be doing more work than that.   It has to be more, that is, than an abstract expression of radical Cartesian doubt.  An absence of metaphysical certainty can be ascribed to any potential evidence from a criminal defendant.  If that were the operative legal standard, it would vitiate the Sixth Amendment right to present a defense entirely -- a holding to which it must be deemed unlikely that eight Supreme Court Justices would intentionally subscribe.

    And of course, on any natural reading, the "no way to know" statement does seem to voice doubts going beyond generalized epistemic anxiety.  It voices actual concern over the quality of the evidence.  Certainly it is normally a bad portent for admissibility, in the Daubert era, if an expert says there is no way to know in any particular case whether the expert's methods have led to accurate conclusions, and that doubts and uncertainties plague the expert's methods in even the best of circumstances.  When the Court in Scheffer says this of polygraphy, it can fairly be read (and the federal appellate courts have usually read it) as saying: Polygraphy is too dubious a discipline for us to feel that a criminal defendant will be denied the benefit of any truly probative testimony if we exclude it.

    So much may be unobjectionable, but having voiced that highly plausible thought, the Scheffer opinion immediately moves to draw a less plausible conclusion: "Individual jurisdictions therefore may reasonably reach differing conclusions as to whether polygraph evidence should be admitted."  Why is this sentence there?  Not only is it in evident dissonance with the Court's "no way to know" and "plagued with uncertainty" observations; it is also a far broader conclusion than the circumstances of the case required the Court to draw.  To uphold a per se ban on polygraph testimony in military tribunals, after all, the Court did not have to go so far as to conclude that reasonable jurisdictions could differ.  It need only have concluded, for the immediate purposes of the case before it, that a reasonable jurisdiction could exclude polygraphy altogether.


    It is beyond the reach of my powers to offer an interpretation that harmonizes "individual jurisdictions may reasonably reach differing conclusions" with "no way to know."   The suspicion naturally arises, however, that with its "reasonable jurisdictions may differ" language,  the Supreme Court was signaling approval of post-Daubert decisions in the lower courts suggesting that polygraph evidence is now admissible in the sound discretion of a trial court, on a suitable foundation.  This is a dark augury, but it draws support from Justice Thomas's inability to collect a Court majority for one of his secondary arguments -- i.e., that "[a] fundamental premise of our criminal trial system is that 'the jury is the lie detector.'"

    Of course, there may be less sinister explanations for the refusal of a majority to join Justice Thomas on this point.  Perhaps some Justices, for example, were concerned that Justice Thomas's arguments about encroaching on the jury function, and also about generating collateral litigation, might send a premature signal concerning the Court's views on other hot evidentiary topics -- e.g., the admissibility of expert evidence on the reliability of eyewitness testimony.


    Daubert and its progeny now lend surprising credence to evidentiary arguments in support of admitting expert testimony from polygraphers, on an ad hoc, case-by-case basis.  From a constitutional standpoint, meanwhile, criminal defendants currently enjoy neither a reliable right to present their own polygraph testimony nor a reliable right to exclude the prosecution's.  The same is true as a matter of litigants' rights under evidentiary law, at least to the extent that Daubert supplies the touchstone.

    There has not yet been a tidal wave of polygraphy in federal courtrooms, but there are portents.  The Tenth Circuit, for example, has upheld, somewhat timorously, a district court decision approving the reliability of polygraph testimony offered by the prosecution in a criminal proceeding.  The defendant in that case, admittedly, had previously stipulated to the polygraph.  But will proponents of polygraphy not say that whether the defendant stipulated to the polygraph is immaterial to the Tenth Circuit's reliability ruling?

    On a dark night, even more Orwellian scenarios may be imagined.  Suppose, for example, that a local public defender's office decides it should allocate more resources to defendants it thinks innocent than to defendants it thinks guilty.  Obviously, the public defender's evaluation of the defendant's probable guilt or innocence would have to be made prior to any trial, but polygraphy could aid in that.  Imagine, then, a murder defendant who vigorously protests his innocence but fails the public defender's polygraph.  Of course, the polygraph is used only by the public defender's office, and only for administrative purposes, and so it has never withstood Daubert scrutiny, by a trial court or on appeal, nor have the polygraph results ever been evaluated by a finder of fact in an adversary process.  Two critical tests of the polygraph's reliability, that is, have never been conducted.  Imagine, nevertheless, that based in part on the polygraph results, the public defender's office assigns the case to an attorney with no prior experience in capital cases, who does a lackluster job, and that the defendant is convicted and sentenced to death, in a case where the defendant's guilt is sufficiently doubtful that when the conviction is finally overturned, years later, for ineffective assistance, the state declines to reprosecute.  Imagine, finally, that the client, now a free man, seeks a civil judgment that the public defender's office -- which is, after all, an arm of the state -- may not constitutionally proceed in this manner.  Will the courts not conclude that if reasonable jurisdictions may differ on the admissibility of the polygraph at trial, then surely a public defender's office seeking to apportion scarce resources among clients may rely on the polygraph for its own internal administrative purposes?  You will say this is a paranoid fantasy.  See Miranda v. Clark County, 279 F.3d 1102 (9th Cir. 2002), overruled on rehearing en banc, Miranda v. Clark County, 319 F.3d 465 (9th Cir.), cert. denied, 540 U.S. 814 (2003).

Kumho Tire