Frequently Asked Questions

 

  

Iíve heard that voice stress analysis is also a very good technique for detecting lies. How come you donít make mention of it at all?

There has been extensive research on voice stress analysis, or CVSA. From 1994 to 1996, 4 separate research studies concluded the following accuracy levels, 37%, 39%, 52% and 50%. This was no better than chance. In 2001, the United States Department of Defense conducted its own studies and field applications into voice stress analysis and concluded that it had an accuracy rate of 0%. As a result, no Department of Defense agency or division utilizes voice stress analysis.  In 2006, the University of Florida did a research study of the latest ďlayeredĒ voice stress instrumentation.  Once again, the accuracy proved to be no better than chance.

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Iím told that if Iím nervous, I could fail the test. Is this true?  

This is a long standing belief that holds no truth whatsoever. Everyone who takes a polygraph examination will be nervous, whether they intend lying in the exam or not. The polygraph exam identifies truth and deception, no matter the level of nervousness in the subject.

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Iíve heard that Polygraphs are not accepted in South African courts?
This is not true. Please see the section on this site called ďLegal StandingĒ to fully answer your question.
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Iíve been told by some people that Polygraphs are not accurate and by others that it is very accurate. Who is right?

If conducted by a highly trained and qualified examiner, the polygraph is astonishingly accurate. Please see the section on this site called ďAccuracy of the PolygraphĒ to answer your question in full. It must be stressed though, that the exceptional validity and reliability figures quoted are contingent on the fact that the examiner is a highly trained and qualified professional. A Polygraph instrument operated by an unqualified person gives justification to those people who say they donít work. Itís the same as putting an unqualified person in charge of the controls of an aircraft. If you had never seen one fly, and were watching this person try and fly it, you would be justified in stating that airplanes donít fly.

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How does the polygraph detect lies?

The short answer is that when we lie to something important, changes occur in our bodies that we have no control over. The polygraph records those changes. To briefly describe this in greater detail Ė one of the two nervous systems in our body is called the Autonomic System. We have no conscious control of this system. The Autonomic System in turn, consists of two systems Ė the Sympathetic and the Parasympathetic. When we lie, it creates physiological changes at the Sympathetic level beyond our control. The polygraph records these Sympathetic arousal responses.  

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Some people say that the polygraph can be beaten if you control your emotions. Is this true?
Refer to the answer above. Sympathetic response cannot be controlled.
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Will it work on someone with no conscience Ė a Psychopath for example?

Research has shown that the Polygraph is just as accurate on Psychopaths (and in fact even more so in many cases) as it is on non-psychopaths. This research has been practical field results, not theoretical academic work.

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How does blood pressure medication, and in fact other medication, affect the accuracy of the Polygraph?
It doesnít.
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Surely youíre biased towards whoever is paying for the exam. If itís a company for example, I find it hard to believe that you wonít give them the result theyíre looking for, right?

Actually in the vast majority of cases, all parties are simply looking for one thing Ė the truth. When we conduct examinations, we are partial to neither party and prejudiced to nothing but the truth. We take no sides beforehand.  If one party however is looking for something different to the truth to be reported by us, then Iím afraid theyíve come to the wrong place. If youíre still not convinced, then please note that we belong to both the American Polygraph Association and the Southern African Polygraph Federation and are therefore bound to codes of ethics as well as standards & principals of practice. Lastly, from a commercial perspective, unethical practice is a sure way to ruin ones reputation and consequently ones business. We will not entertain it in the slightest.

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