Polygraphs and Voice Stress Analyzers as Interrogation Tools
Prepared for Wisconsin Criminal Justice Study Commission by Dan Blinka
When the Commission addresses the subject of “deception” as a police
interrogation tactic, special consideration should be given to any mention of polygraphs
and voice stress analyzers. There are several related issues.
First, Wisconsin case law clearly and emphatically forbids any mention of
“polygraphs” at trial, criminal or civil. This is a broad exclusionary rule that includes not
just the result of a test, but virtually any mention of even a request to take one – whether
the request originates with the police or the suspect. There is, however, one narrow
exception: “an offer to take a polygraph is relevant to the state of mind of the person
making the offer as ‘long as the person making the offer believes that the test of analysis
is possible, accurate, and admissible.’” Put differently, the suspect (the “offeror”) must
be mistaken, confused, or ignorant about the law, which deems polygraphs neither
accurate nor admissible. See Estate of Neumann v. Neumann, 2001 WI App 61, 242
Wis.2d 205, 626 N.W.2d 821, ¶ ¶ 64-67. Paradoxically, police may foster this very
confusion by using the polygraph as a wedge during interrogation.
This leads to my second point: In light of this broad exclusionary rule should
police request or even suggest that suspects take such a test? The deception is subtle.
Most suspects, particularly those unrepresented by counsel, have no idea that the outcome
of a polygraph or voice stress analyzer, regardless of how carefully done, is not
admissible in court because of the substantial misgivings about the reliability and validity
of such tests. Nor would some form of “warning” suffice, as they’d have to be prolix and
necessarily misleading. Why would a suspect take a voice stress analyzer that would be
inadmissible even if it showed him to be “truthful”? The case law more or less intimates
this same point when it questions why a “competent” defense lawyer would recommend
that his client take a polygraph. See State v. Phaff (below). Note: we are not addressing
a scenario where defense counsel is bargaining for immunity or other concessions and the
polygraph offers represents some sort of bona fides. In these cases, the suspects
statements are likely protected by Wis. Stat. § 904.10, which would forbid their use at
trial.
Third, since present law requires that interrogations be recorded, it follows that
any mention of polygraphs, etc. must be deleted before the recorded statements may be
introduced at trial. Aside from the expense and inconvenience of such edits, a jury will
be left to speculate about what are likely to be obvious “gaps” in the recording. (Video
recordings are likely to feature date/time generators.) And regardless of a judge’s
cautionary instructions (“. . . you are not to speculate about what was deleted . . .”), it is
highly likely that the jury will do just that. Cases in which a suspect initiates the problem
by innocently requesting a polygraph are likely to be few and can be readily handled
under existing law. But if police are permitted to broach the subject as a matter of
interrogation protocol, the cases and issues are likely to be multiplied. Simply put, I
don’t think we should license law enforcement to wreak this kind of havoc with criminal
trials.
Selected Cases.
Estate of Neumann v. Neumann, 2001 WI App 61, 242 Wis.2d 205, 626 N.W.2d 821, ¶
63 (holding that polygraph evidence is inadmissible in civil cases as well as criminal
cases; it also rejects the argument that experts should be permitted to testify that they
relied in part on the results of a polygraph; such testimony, said the court, “would inform
the jury that a polygraph had been taken and allow the jury to infer that those results were
favorable to Neumann. The effect would be the admission of polygraph results, which
we have already concluded are inadmissible”).
State v. Pfaff, 2004 WI App 31, 269 Wis.2d 786, 676 N.W.2d 562, ¶29 (holding that the
trial court properly exercised its discretion in excluding defendant’s offer to take a
polygraph, an offer made at the suggestion of his lawyer: “When the offer to take a
polygraph test originates with the defendant and is accompanied by the defendant's belief
that the test result or analysis is ‘possible, accurate, and admissible,’ it is probative as
‘consciousness of [the defendant's] innocence.’ The converse does not hold when the
offer to take the test is the result of an attorney's suggestion or direction. Any competent
defense attorney practicing in Wisconsin well knows that polygraph test results are
inadmissible in this state, and presumably the attorney would share that knowledge with
the client when suggesting the test.”) (citation omitted).
State v. Greer, 2003 WI App 112, 265 Wis.2d 463, 666 N.W.2d 518, ¶16 (holding that a
“post-polygraph interview” was adequately set apart from the polygraph examination
itself and thus not fatally tainted despite the polygraphist’s declaration that defendant had
failed the test: “As long as there is both a sufficient temporal separation and a sufficient
spatial demarcation between the examination and the post-examination interview, and the
defendant is told that the polygraph test is over, letting the defendant know that he or she
did not pass the examination, or letting the defendant so conclude, does not negate that
the examination and the post-examination interview are . . . ‘totally discrete’ events rather
than ‘one event.’”) (citation omitted).
State v. Frank, 2002 WI App 31, 250 Wis.2d 95, 640 N.W.2d 198, ¶¶23-24 (concluding
that no “polygraph” evidence was presented to the jury where a witness was identified to
jurors as an “expert forensic interviewer” and “never mentioned the word polygraph in
his testimony”).