In these studies, when evidence that the defendant
failed a polygraph test is introduced into the trial, it
consistently has failed to affect verdicts or measures
related to verdicts (e.g., confidence ratings, strength
of evidence ratings). In comparison, in studies in
which other forms of equally suspect evidence are
also introduced—such as eyewitness testimony,
participants have tended to rely heavily on this infor-
mation when rendering judgments. Moreover, partici-
pants fail to draw a distinction among the different
types of polygraph test evidence. For example,
research has consistently shown that the Guilty
Knowledge Test (GKT) is much less likely to result in
false positives (i.e., truthful suspects misclassified as
deceptive) than is the CQT. Yet when studies have var-
ied the type of polygraph test admitted in instances
where the defendant failed the test, again no differ-
ences were found. That is, participants are no more
trusting of the GKT than they are of the CQT. When
researchers have varied whether the polygraph test
results indicated that the defendant had passed the test
or failed the test, there were again no differences in
verdicts when compared with a control group that did
not receive polygraph test results in the trial. Finally,
because it is possible that participants are less apt to
rely on polygraph evidence when other, more reliable
forms of evidence are present than when it is the sole
evidence against the defendant, researchers have var-
ied the presence of failed polygraph evidence both
with and without other corroborating evidence. Again,
no differences were found for guilty judgments, as
participants were no more likely to rely on polygraph
evidence when it was the chief evidence against a
defendant than when it was one of many pieces of evi-
dence against the defendant.However, whereas jurors are rather reluctant to use
polygraph evidence in their decisions, the general
public appears to be less skeptical of the test than are
experts. That is, surveys of experts in areas such as
psychophysiology suggest that compared with the
general public, they are more uniformly condemning
of the value of polygraph tests. The general public
tends to be more varied in its beliefs. Moreover, the
general public is less inclined to perceive subtle dif-
ferences in the techniques (e.g., CQT vs. GKT) but
rather holds a generally skeptical attitude toward all
polygraph tests. What is clear, then, is that despite the
opinions of many within the legal community who
fear that polygraph evidence may be overly probative
in the minds of jurors, the research thus far is consis-
tent in demonstrating that neither are polygraph test
results highly valued by jurors nor do jurors place
unwarranted trust in the test when rendering judg-
ments concerning the defendant.Bryan MyersSee alsoDetection of Deception: Use of Evidence in;
Detection of Deception in Adults; Polygraph and
Polygraph TechniquesFurther Readings
Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993).
Frye v. United States, 293 F. 1013 (D.C. Cir. 1923).
Lykken, D. T. (1998). A tremor in the blood: Uses and abuses
of the lie detector(2nd ed.). New York: Plenum Press.
Myers, B., Latter, R., & Abdollahi-Arena, M. K. (2006). The
court of public opinion: Lay perceptions of polygraph
tests. Law and Human Behavior, 30(4), 509–523.
United States v. Alexander, 526 F.2d 161, 164 (8th Cir. 1975).Public Opinion About the Polygraph——— 665P-Cutler (Encyc)-45463.qxd 11/18/2007 12:43 PM Page 665