After interviewing polygraph experts at the CIA (news - web sites), FBI (news - web sites) and
other agencies, the panel of the National Academy of Sciences (news - web sites)
determined that it is possible to fool a lie detector,
especially if the subject is being screened for general
criminal or spy activity and not for some specific act.
The academy committee, appointed at the request of the
Department of Energy (news - web sites), decided that polygraphs cannot be relied
on for mass screening of federal employees because they can
falsely suggest an honest employee is lying and can be fooled
by someone who is trained to do so.
"The US federal government, through a variety of agencies,
carries out thousands of polygraph tests each year on job
applicants and current employees, and there are inevitable
disputes that are sometimes highly publicized when someone
'fails' a polygraph test," the panel, made up of professionals
who have never worked with lie detectors, wrote in its report.
"Over 19 months, the committee held a series of meetings,
visited polygraph facilities at several government agencies,
and examined large numbers of reports and published papers," it
added. "We attempted to listen carefully to people representing
both sides in the debate on polygraph accuracy, and we then
stepped back and reviewed the evidence ourselves."
Sometimes polygraphs can work, they decided--although
something better is clearly needed.
"We conclude that in populations of examinees such as those
represented in the polygraph research literature, untrained in
countermeasures, specific-incident polygraph tests can
discriminate lying from truth telling at rates well above
chance, though well below perfection."
But the lie detector can be fooled by someone who has
training--which, in the case of government agencies, would be
precisely the people they are trying to screen out.
"Certain countermeasures apparently can, under some
laboratory conditions, enable a deceptive individual to appear
nondeceptive and avoid detection by an examiner," the report
reads.
"Overconfidence in polygraph screening can create a false
sense of security among policy makers, employees in sensitive
positions, and the general public that may in turn lead to
inappropriate relaxation of other methods of ensuring
security," it adds.
"Its accuracy in distinguishing actual or potential
security violators from innocent test takers is insufficient to
justify reliance on its use in employee security screening in
federal agencies."
The report noted that sometimes a person appears to be
lying on a polygraph when in fact he or she is
anxious--especially if that person is from a "socially
stigmatized" group.
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