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Q: is there any proven form of lie detection? ( Answered,   5 Comments )
Subject: is there any proven form of lie detection?
Category: Reference, Education and News
Asked by: madmary1000-ga
List Price: $10.00
Posted: 31 Jul 2002 01:17 PDT
Expires: 30 Aug 2002 01:17 PDT
Question ID: 47293
is there any proven form of lie detection?
Subject: Re: is there any proven form of lie detection?
Answered By: huntsman-ga on 31 Jul 2002 05:13 PDT
If there was a foolproof lie detector, other than Mothers, perhaps we
wouldn't need juries or judges.

Basically, lie detection techniques rely on the assumption that we get
nervous when we lie, and this shows up in physical and physiological
signs such as: fidgeting; averted eyes; dry mouth; sweaty palms; rapid
breathing; a red face; speaking difficulties, and other symptoms.
However, these signs are not always signs of deception: they can
easily be caused by tension or stress, particularly when we feel like
we're in deep trouble.
For centuries, experienced individuals -- priests, investigators,
police, and even criminals (jailed in the company of convicted liars)
-- have consciously or subconsciously used these signs to recognize
lying. But their effectiveness can be pretty subjective, and their
skills can take a lifetime to learn.

In an attempt to get consistent, repeatable results in a shorter time,
several "lie detection" machines and techniques have been developed,
mainly within the last 100 years or so.

The oldest, best known and most reliable of these is the polygraph.
Set up and operated by a skilled examiner, a polygraph uses several
physiological symptoms to infer if any deception has occurred:

   - Breathing rate: detected by tubes around the chest 
   - Perspiration: detected by metal electrodes on the fingers
   - Blood pressure, pulse rate: detected by a pressure cuff on the

Electrical wires from these sensors are attached to a console with
pens that writes their signals onto a roll of moving paper, much like
a seismograph. A picture and detailed explanation of polygraph
operation can be seen here:

   Scientific Lie Detection  

Computerized polygraphs are also available that work with PCs. Here is
a large image of one system and its various components:

   Axciton Systems Inc
   Axciton Unit

Although helpful during investigations, polygraph examinations are not
foolproof and depend heavily on the training, interviewing skills, and
diagnostic abilities of the examiner. It's not just the machine that
does the work: an effective polygraph exam also depends on the nature
of the questions asked and an expert analysis of the results.

Wily subjects can adversely affect polygraph accuracy by consciously
adjusting their normal "control" levels of breathing, perspiration,
and blood pressure/pulse rate during the setup phase. If their normal
levels are abnormally elevated, then the examiner may not be able to
detect truly abnormal symptoms when a lie is being told during the
normal questioning phase. Uncooperative, antagonistic subjects can
also affect the results.

Polygraph evidence can be admitted in court in some states, but
primarily if the defense and the prosecution have specifically agreed
to it before the trial begins. Because of various legal complications,
many states don't allow polygraph tests to be admitted, and criminal
suspects are not required to take a lie detector test before trial.

Another type of lie detector is the "Psychological Stress Evaluator"
(PSE), which relies on an audio technique called "Voice Stress
Analysis" (VSA). This system allegedly detects and analyzes small
voice tremors and changes in pitch, but it has not been conclusively
proven that these are a sign of deception. One vote against this
technique is that while American military services use traditional
polygraphs in their investigations, they do not use PSE/VSA systems. 
Like the physiological symptoms detected by the polygraph, voice
tremors may also be caused by stress or can be affected by deliberate
actions of the subject.

"Narco-analysis" is the injection of "truth serums", such as sodium
pentothal or scopolamine. The purpose of these drugs is not
necessarily to detect lies, but to relax the subject enough so they
have fewer inhibitions about hiding the truth. However, the
effectiveness of these drugs has not been scientifically proven and is
inadmissible in court.

One recent development in lie detection is based upon the premise that
different areas of the brain are active while a lie is being told.
Another technique, developed by the Mayo Clinic, uses a heat-sensing
camera to measure heat patterns caused by increased blood flow to the
face when someone is lying.

Unfortunately, none of these methods are yet 100% accurate in all
cases, and so there remains a reasonable doubt about their use in
court proceedings.

Thank you,

References - 

   American Polygraph Association


   The Crime Library
   The Polygraph

   Federation of American Scientists
   Scientific Validity of Polygraph Testing

   FindLaw's Writ
   On Lie Detection

   MegaLinks in Criminal Justice
   Scientific Lie Detection

   Mayo Clinic
   New Technology Detects Lying

   Popular Science
   Liar, Liar Pants on Fire,12543,330055,00.html

   Scientific Lie Detection 

Search Terms & Google Results - 

   lie detection

   voice stress analysis   

Request for Answer Clarification by madmary1000-ga on 31 Jul 2002 06:35 PDT
ok, so is there any proven form of lie detection, proven as in scientifically proven

Clarification of Answer by huntsman-ga on 31 Jul 2002 07:49 PDT


As several of the Web links point out, there are no forms of lie
detection that are 100% accurate with all subjects. Although the
polygraph is considered by many as the oldest and most reliable
"technical" method, its methods still do not catch every lie, or
expose every liar.

For example, note the study at:

   Federation of American Scientists
   Scientific Validity of Polygraph Testing

In the Conclusion of Chapter 3
(, the
author states:

"Central to legal, legislative, and scientific assessment of polygraph
tests are their validity. Yet, despite many decades of judicial,
legislative, and scientific discussion, no consensus has emerged about
the accuracy of polygraph tests."

In other words, sometimes the magic works, and sometimes it doesn't.

Subject: Re: is there any proven form of lie detection?
From: wengland-ga on 31 Jul 2002 06:56 PDT
Not with 100% certainty, no, there is not.  The polygraph is as close
as you can get to 'proven'.
Subject: Re: is there any proven form of lie detection?
From: expertlaw-ga on 31 Jul 2002 07:58 PDT
It is important to recall that a "lie detector" - even a perfect one -
can only detect intentional deceit. It won't do a thing to detect
deviation from the truth, where the person being tested believes the
statement to be true. So the concept of a "lie detector" - a machine
that could in theory tell you when somebody is being intentionally
deceitful - should not be confused with a "truth detector".
Subject: Re: is there any proven form of lie detection?
From: cephalic-ga on 01 Aug 2002 12:10 PDT
Nothing can be "proven scientifically".  Although the theory of
gravity seems a very good and well supported explanation of why your
pen drops to the floor when you let go of it, the theory of gravity
remains unproven.  That is, there exists a universe of possible
explanations for why your pen drops to the floor - many of which
cannot be tested.  For example, if I were to suggest that an invisible
person (that cannot be detected with any of your senses, nor using any
device that exists or that could ever be built) is responsible for
taking your pen and placing it on the floor, you could not disprove my
claim.  Oh, by the way, this person is everywhere at all times and is
infinitely large which explains how gravity works on planets.... you
get the idea.

Subject: Re: is there any proven form of lie detection?
From: fstokens-ga on 09 Aug 2002 15:56 PDT
Since most (all?) "lie detectors" work by measuring
stress/nervousness, there are a couple fundamental problems that I
haven't seen mentioned.

1) People who are particularly ethical or imaginative may become
distressed at the *idea* of committing a crime, even if they are
innocent.  A lie detector may falsely accuse these people.

2) A true sociopath, someone who does not know or care the difference
between right and wrong, will feel no distress at lying, and may be
cleared by a lie detector.
Subject: Re: is there any proven form of lie detection?
From: huntsman-ga on 19 Aug 2002 11:58 PDT
Here's a recent article that comes to the same "inconclusions":

   Washington Post - TechNews.Com
   Lie-Detecting Devices: Truth or Consequences?
   Sunday, August 18, 2002


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