On Tuesday, 28 July 2009, the British tabloid
The Sun published an
article by chief reporter John Kay on a 3-year pilot project by the UK Ministry of Justice to subject some 450 sex offenders to post-conviction polygraph screening. Kay sat in for a polygraph screening examination administered in Birmingham by US polygrapher Bill Scheve. Apparently relying on Scheve as his source, Kay reports: "It is virtually impossible to trick a lie-detector because it picks up signals of fear, which emanate from the hypothalamus gland in the neck."
Of course, this is laughably absurd. Or it
would be laughable were the matter at hand not so serious. All that one needs to trick a lie detector is an understanding of the trickery on which the "test" itself depends and to covertly augment one's physiological reactions to the "control" questions, as is explained in detail in Chapters 3 & 4 of AntiPolygraph.org's free book,
The Lie Behind the Lie Detector (1 mb PDF).
Kay lists the questions that are asked on the polygraph screening exams as follows:
Quote:DO you intend to answer each question truthfully?
DO you consider yourself to be a sex offender at risk?
HAVE you lied to any family or friends since your release from prison about anything serious?
SINCE your release have you been alone with anyone you knew was under 18?
SINCE your release have you violated any rules or conditions of your license?
The first question is a prototypical "sacrifice" relevant question and would not be scored.
The second and third questions, while appearing relevant, are actually probable-lie "control" questions. It is secretly assumed that even sex offenders who have not violated the terms of their probation will show a reaction to these questions.
The last two questions listed are the relevant ones -- the
only ones that the probation department is
really concerned about.
All that British sex offenders who have violated the terms of their probation and are subjected to such a screening "test" need to do in order to fool the lie detector is to 1) make no damaging admissions and 2) augment their reactions to the 2nd and 3rd questions listed above. This can be done by covertly biting down on the side of the tongue, thinking exciting thoughts, or doing mental arithmetic.
Far from it being "virtually impossible to trick a lie-detector," as Kay reports, it's quite simple. And it's no doubt going to happen.