When it comes to authorities trying to determine if a person, a suspect or a subject is being deceptive, they make use of the instrument that is called the polygraph.  It’s most popularly known as the lie detector.  This machine measures and makes a record of the subject’s physiological indices while the subject is being asked as series of questions.  The polygraph machine works in a way that it indicates a person is lying when certain physiological responses are made.

In more detail, the polygraph comes with a number of sensors.  These are attached to the subject in various parts of his body in order to measure pulse, blood pressure, respiration and even skin conductivity.  At the beginning of the polygraph test, the examiner will ask the subject a few base questions to determine the subject’s normal rate for those physiological indices.  Then questions about the issue are asked.  In many cases, significant changes like increase heart rate when a specific question is asked indicates that the subject is lying.

For the value it provides in solving and closing cases, many government agencies make use of the polygraph.  Agencies like the CIA, FBI and even police departments like the LAPD use lie detectors in their work.  If they have a case where stories of suspects are doubtful, the suspect is made to go through a polygraph test.  The polygraph results after being interpreted by an examiner can be used in court cases to exonerate or condemn a suspect in a case.