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      Who should Take polygraph Test

      Generally, any person who desires to verify their truthfulness regarding a specific situation or incident is a good candidate for a polygraph. Any person who intends to lie or withhold any relevant information about the issue under consideration should most certainly not take a polygraph test.

      How accurate is the polygraph?

      • U.S. Government studies have concluded that when a qualified examiner conducts the test properly, the polygraph exam is 95 percent accurate.The latest research by the Department of Defense has shown a professionally administered polygraph examination to be approximately 98% accurate.It is the most accurate means available for determining the truth or deception of a person answering a direct question in a court.

      Does a person’s high blood pressure affect the polygraph test?

      • No. While blood pressure is one of the physiological reactions measured, it does not affect the accuracy of the polygraph test.

      Will drugs or alcohol affect the accuracy of a polygraph test?

      • Contrary to what many think, the use of drugs and/or alcohol will not assist someone to beat a polygraph test. Polygraph examiners utilize certain procedures during a polygraph test ensure that each person taking a test is responding naturally throughout the testing procedure. If you are taking any medication you need to inform the polygraph examiner prior to beginning the test. Physiological affects that drugs have on people are immediately seen in polygraph chart tracings. Irregular physiological recordings must be satisfactorily explained.



How does the polygraph work?

When a person perceives a threat, the body reacts to the threat. This is referred to as the "fight or flight" reaction, as the body readies itself either to fight off the threat or to flee. When a person tells a lie, it is because for some reason, the truth constitutes a threat to that person.


Consequently, certain physiological reactions take place in the person's body which he/she cannot control and which can be measured by the polygraph (See "Human physiology: a basis for the detection of deception" on our web site for more details).


A polygraph instrument collects physiological data from at least three systems of the human body. Pneumograph tubes are placed over the examinee's chest and abdominal area to record breathing patterns and finger plates are attached to the fingers to record sweat gland activity.


A blood pressure cuff will record cardiovascular activity.

The reactions are charted by the polygraph instrument and reflected on charts printed from the recordings.