|The Polygraph Test: An Overview
|By Ken Blackstone
John F. Kennedy stated: “The great enemy of the truth is very often not the lie - deliberate, contrived and dishonest, but the myth - persistent, persuasive and unrealistic” (1962 Yale University) and today, the most persistent enemy of those who could benefit from forensic polygraph is a surplus of myth and misconception about the polygraph.
So, what does the polygraph do?
One of the most misleading myths regarding the polygraph procedure is the term lie detector and the subsequent assumption that there is a physiological response that is unique to lying. Sorry – there is no Pinocchio response.
Analog or digital, the polygraph instrument does not detect lies; it records respiration, electrodermal activity, and cardiovascular activity and that recording translates into a monitor of the autonomic nervous system (ANS).
How good is a polygraph test?
Polygraph test is a catch-all term that describes a spectrum of applications and techniques. The most accurate of these is the single-issue detection of deception test using a specific technique called the Utah Technique. The Utah has an overall accuracy of 93.9%.
Can someone beat a polygraph?
No. The Utah, and any other technique is simply a measure of a natural and involuntary response, what is called sympathetic arousal, for it is “arousal of the sympathetic branch of the autonomic nervous system.” Everyone has an autonomic nervous system with a sympathetic branch.
Can countermeasures “beat” the polygraph examiner?
Yes. Countermeasures are a serious problem when an examiner has little experience and/or supervision, but countermeasures do not reverse the physiological results. In such a situation, which amounts to the polygraph examiner being dominated by the examinee, there is a mixture of poor interviewing by the examiner and mental countermeasures by the respondent.
Can specific countermeasures “beat” the polygraph by reversing responses?
No. In a series of studies experimental psychologist Charles Honts found that “without special training in countermeasures (subjects) are unable to beat the polygraph test, even if they have been provided extensive information and suggestions on how they might succeed (Honts, 1987). Countermeasures exist, but they usually identifiable and they cannot reverse “deceptive responses”. This makes mental countermeasures, which are not visible in tracings, the only possibility.
Moreover, neither physical nor mental countermeasures have any effect on electrodermal activity (EDA). This can be explained by the fact that the lungs and heart are controlled both by the parasympathetic and sympathetic branches, but the skin is limited to sympathetic control. For example; positive EDA and no significant activity in the other channels is often a sign of deliberate countermeasures.
Didn’t Aldridge Ames “beat” the polygraph?
No. Aldridge Ames, the CIA employee who was caught selling top secret information, now brags from his prison cell that he beat the polygraph and the CIA itself agrees that Ames successfully beat the polygraph (Barland, 2011) (Hanford) (Senate Select Committee on Intelligence). It appears to me that he beat the CIA protocol in the first instance and the examiner erred in the second, but he did not beat the polygraph.
On the first of two polygraphs following the onset of his espionage, Ames was deceptive (DI) but managed to avoid consequences by feeding spurious but plausible explanations to the examiner (I call this throwing a bone). Years later he took a second CIA test and cleared it (NDI). It was after his apprehension that the FBI reviewed the charts and said they were actually DI. (In all fairness, this was with the aid of hindsight.) The CIA has since changed from its “clinical scoring” protocol.
What about psychopaths –aren’t they wired differently than normal people?
In the 2004 movie “Collateral”, the hit man Vincent arrives in Los Angeles, hires a cab, and goes on a killing spree. During the first stop, the hit man shoots a man who falls from a high building onto the cab. The innocent cab driver Max jumps out of the cab and screams at Vincent about killing the man, to which he calmly replies:
Myth: Vincent and everyone else with such a personality will somehow be immune to a polygraph examination.
Fact(s): The polygraph instrument is a monitor of the autonomic nervous system (ANS) and the ANS is not controlled by the value system. While it is true that Vincent and other sociopaths or psychopaths are pathological liars without shame or guilt for their crimes or empathy for their victims, it is not remorse that the polygraph measures.
Yes, the first court ruling, what we call the Frye rule, was in 1923 and the device used was not a polygraph. It was an experiment and compared to the polygraph today, it was primitive. Today, there are standards, supporting research in the relative sciences of physiology and psychology and there have been great improvements in the instrument that is used.
Should polygraph results be used more frequently?
Yes. The rules of evidence in any jurisdiction depict what hoops the examiner and examination must jump through to be admitted as evidence. Polygraph examinations meet that criterion, but, because of tradition, the polygraph has been ignored.
Are there legal obstacles? What are they?
In 19 states the polygraph is only admissible in the guilt phase of a trial only after stipulation between prosecution and defense. Different jurisdictions apply these rules differently. New Mexico is the only state that has ‘open admission’ but they have strict rules of evidence so that only correctly administered by credentialed examiners examinations can be admitted. The Federal and Military Courts have similar rules.
Should they be revisited?
Yes, testing should be admitted in all jurisdictions just as it is now acceptable in NM and in Federal and Military Courts. Why? The prejudice against the polygraph is unfair to innocent persons who are charged with crimes because they are deprived of the only test shown to address the veracity of a statement. People are convicted every day based on statements, statements of alleged victims and alleged witnesses. The prosecution, because it is supposed to be interested in convicting guilty persons, should also welcome the polygraph.
The fact that the polygraph is used in all states during the management of convicted sex offenders and the fact that the outcome of those tests impacts the decisions of treatment providers and supervising officers both are reason to put the polygraph under the scrutiny of a court.
How can the courts establish rules of evidence and then ignore evidence that matches those rules?
About the Author
Editor's note: Corrections.com author, Ken Blackstone is an expert regarding polygraph examinations. He is the author of the book "Polygraph, Sex Offenders, and the Court". Since 1979 he has been involved in more than 23,000 polygraph examinations as an examiner, consultant, and expert witness. He has conducted more than 15,000 examinations and consulted on a thousand more, including several high profile cases (including the Jon Benet Ramsey case and the Troy Davis case). He has written numerous peer-reviewed articles on polygraph and forensic interviewing. The majority of his career has focused on sexual offense cases and the examination of convicted and/or committed sexual offenders. He lives in Stone Mountain, Georgia.
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