What is a Polygraph?

What is a Polygraph?

A Polygraph instrument, or "lie detector", was designed to detect and record deception.  The theory is that when a person lies, it causes a certain amount of stress which in turn produces measurable involuntary physiological reactions.

When taking a polygraph, the test subject will have a number of different sensors attached to their body.  The polygraph measures changes in breathing, blood pressure, pulse and perspiration.  It then records the data as the subject answers questions posed during the examination.  In the case of the older Analog Polygraph instrument, the results are penned on graph paper. With the new modern Digital Polygraph instruments, the data is recorded and displayed on the computer screen and can be printed later.  During the testing process, the polygraph examiner asks a series of questions that establishes a pattern of how an individual responds when giving true and false answers.

At the federal level alone, the polygraph is used extensively in counter-intelligence, counter-terrorism, and counter-narcotics programs.  Additional federal law enforcement uses include: criminal investigations, intelligence operations, presidential protection and nuclear materials containment.  There are at least 68 countries world-wide where the polygraph is used for similar applications.  In the private sector, polygraph is used extensively by individuals, families, therapists, attorneys, courts and businesses where knowing the truth is of the utmost importance.