Distrustful,
Thanks for posting this. The article is by the publisher of
The Blues Police Newspaper, Sgt. Buddy Williams of the Houston Police Department, who describes himself as a former polygraph examiner.
I'd like to comment on just a few of the statements Williams makes in his article.
Quote:But don't be too quick to judge a subject's ability to manipulate his or her bodily functions thereby neutralizing the polygraph's effectiveness. Try raising your blood pressure, evening out your breathing patterns and stop perspiring simultaneously for ten minutes...while answering questions...without a good examiner knowing you are doing it. I've seen many people try it, and it's impossible.
Nonsense. There is no scientific evidence that polygraph examiners -- however "good" -- are able to detect sophisticated countermeasures attempts at better than chance levels of accuracy. In addition, attempting to stop or reduce perspiration is not a productive countermeasure. But increasing one's rate of perspiration by biting one's tongue or thinking exciting thoughts while answering the so-called "control" questions
is an effective countermeasure. See Chapter 4 of
The Lie Behind the Lie Detector for further details about polygraph countermeasures.
Quote:But, you say, since simply taking a polygraph test is enough to give anyone the heebie jeebies, wouldn't an innocent person's nervousness make them look like they were lying? Truth is...if the examiner is not on his toes...maybe. But if the examiner knows his or her stuff, nervousness would not be interpreted as deception.
Mr. Williams' claim that nervousness won't be interpreted as deception if the examiner "knows his or her stuff" is untrue. As David Lykken has noted, the polygraph pens don't do a special dance when a person lies. Any innocent subject who is more nervous about the relevant questions than about the so-called "control" questions is likely to become a false positive. See Chapter 3 of
The Lie Behind the Lie Detector for further details.
Quote:You can beat a polygraph test by taking a sedative before the test, or by putting a tack in you shoe and stepping on it when you answer a question.
False: A good examiner can easily detect that the subject has been medicated or is artificially stimulated. Furthermore, the examiner can safely assume only a deceptive subject would not tell the examiner about the drug or tack effects prior to the test.
While taking a seditive is not an effective countermeasure for the "control" question "test," the tack-in-the-shoe trick may well work, if pain is applied only when answering the "control" questions and if the polygraph chair is not equipped with a strain gauge. Physiological reactions induced by self-stimulation have not been shown by peer-reviewed scientific research to be distinguishable from those resulting from fear of being caught in a lie.
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