Lie testing

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Lie testing

Lie testing, or polygraph testing, is the measurement of the changes in the autonomic nervous system to identify truthful answers.

Why conduct lie tests?

A lie test is an investigative technique to detect the truth of a particular statement. When there is a family or personal matter that cannot be resolved the lie test may give you peace of mind that no other means has been able to.

It can be used in matters such as:

  • Family disputes.
  • Infidelity disputes.
  • Drug use disputes.
  • Accusations of sexual misbehaviour.
  • Accusations of theft.

How accurate is the lie test?

The polygraph technique is very accurate, however, it is not infallible, and in some cases results may be inconclusive.

According to the American Polygraph Association, which has reviewed over 250 studies conducted over the past 25 years on the accuracy of polygraph testing, it is estimated that the accuracy of the results is in the range of 90 - 95%. More recent research has shown that the accuracy of computerized polygraph testing is 98%.

How does the lie test work?

A lie detector test is, in effect, a medical instrument which measures changes in the autonomic nervous system. It uses three instruments to measure changes:

  • Pnuemograph - Two rubber pnuemograph tubes are placed around the upper chest and abdomen; these record breathing and movement.
  • G.S.R - The GSR or galvanic skin response is measured by placing two fingerplates across the ring and index finger of the right hand. These monitor changes in skin resistance during the examination.
  • Cardiosphygmograph - This traces changes in the blood pressure and pulse rate, and is similar to the pressure cuff a doctor uses to take your blood pressure.

When someone is telling a lie there is an autonomic reaction in the body that is measured by the instruments. The analysis of the measurements enables the polygraphist to give a view on the truthfulness of the answers to the questions posed.

Can the polygraph test be beaten?

Provided the examiner conducting the test is trained and qualified it is highly improbable. The lie test is a very effective measure of truthfulness; however, it may not be conclusive in all cases.

I am nervous about taking the test. Will this affect the results?

It is quite normal for an innocent person to feel nervous. The polygraphist will use techniques to eliminate this from the results.

What happens at the Lie Test

The lie test takes about 2 hours to conduct. It is divided into three steps.

Pre-test interview

During the pre test interview the examiner will

  • Explain how the polygraph works.
  • Discuss the specific issue.
  • Develop and review all the questions to be asked on the polygraph test.

This stage is normally the longest to complete and can take anything from 45 to 90 minutes.

Test questions

During this step the subject will be attached to the polygraph. The set of questions, which was developed during the pre-test interview, will be asked several times. During this stage only the examiner and subject will be present.

Results analysis

Once the examiner has collected the measurements he will analyse the results before giving a decision as to the subject's truthfulness or deception.

The results is generally available at the conclusion of the test. A written report is available a few days later if this required.

Where are lie tests taken

Lie tests can be conducted at any quiet location where the test will not be interrupted or affected by external noise. This can be at your home, at an office, or at a hotel room. The polygraphist will travel to a suitable location neat to you. It is not necessary for you to travel to a central office to be tested.

I have questions

Please get in touch with your local office to discuss your situation and to arrange a lie test.

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