Even though scientists question the accuracy of lie
detectors, the CIA, FBI, and other federal agencies use polygraph machines to
screen applicants and to hunt for lawbreakers. There are many researchers and
defense attorneys who say polygraph is prone to a higher number of false
results. Despite this it has emerged as a tool in the CIA’s effort to identify
suspected leakers of government anti-terrorism tactics.
The polygraph machine measures various physiological
changes such as blood pressure, respiratory rate, heart rate, and
electro-dermal activity (sweat). The point is to determine when subjects are
getting anxious. The idea is that deception involves an element of anxiety. The
clincher is that an emotion (anxiety) can be triggered by many factors other
than not telling the truth. As a result the experts feel that the tests can
overlook smooth-talking liars while indicating innocent people who are simply
rattled.
Polygraph tests results are generally inadmissible
in federal courts and most state courts. On the other hand, statements or
admissions made during the course of the test can be used in court. Some people
seem to feel some of the polygraph’s value is in prompting people to tell the
truth.
Questions which focus on whether people have memory
of a certain event give far more reliable results than screening tests which
rely on emotions triggered by a wide range of factors.
Polygraph examinations are designed to observe
significant involuntary responses going on in the person’s body when that
person is subjected to stress, such as the stress associated with deception.
The exams are not capable of detecting if the person is lying.
How do liars beat the test? The exam is started out
with baseline questions which provide the examiner with baseline physiologic
responses. The liars simply increase their physiologic responses with exciting
thoughts, altering one’s breathing pattern, or biting the side of their tongue.
All these measures increase all the physiologic parameters that are being
measured, thus providing these false numbers as their baseline. When later in
the exam they tell a lie, these increased parameters are compared to the false
baseline parameters and are viewed to be normal.
If you use the lie detector in your story, you may
want to keep in mind how it is viewed, how it works, and how it can be beat.
Lie detector results are not considered as valid by some and are not allowed in
most courts. Remember that it cannot detect a lie, only if there is possible
deception. And most of all, that the lie detector can be beat by someone who
knows how.
Faye
M. Tollison
Author
of: To Tell the Truth
Upcoming
books: The Bible Murders
Member
of: Sisters in Crime
Writers on the Move
www.booksinsync.com
