The Polygraph Examination

How It Works

When a person lies, they are afraid of being caught. They will feel the same way as when they are afraid of any other threat (Heart rate increases, perspiration increases, subtle changes in breathing occur).

When a person tells the truth and does not lie, they are not afraid. Since they are not afraid, there will be no reaction (Their body will be at Homeostasis or a Steady Rate of Balance). Keep in mind that each polygraph test is not just one test but is actually a series short tests (or charts) that make up the complete test (usually 3 to 5 charts). The truthful person will get increasingly better with time but the deceptive person will get worse as the test goes on.

That is why the polygraph instrument is so effective. It provides the examiner with the physiological data needed to tell if the person undergoing the exam is being truthful or deceptive.

We use equipment manufactured by Stoelting. Since 1930, Stoelting has been at the forefront of design and manufacture of reliable polygraph instrumentation. Our third generation Computerized Polygraph System (CPS) represents the very latest in state-of-the-art digital technology and innovation.

The examination is completely painless and does not use injections, shock, or drugs. During a test…

  • The tubes around the chest and abdomen expand and contract with each inhale and exhale
  • The blood pressure cuff reads changes in blood pressure and blood volume in the skin’s tissue
  • The electrodes send readings of electrical current variations to a galvanograph unit. These readings are sent and processed by the equipment used during the examination, to which the examiner will operate and monitor.

A polygraph is an instrument that records what takes place inside of your body when you are asked a question. The polygraph instrument is essentially a pneumatically operated mechanical recorder of changes in blood pressure, pulse, and respiration, supplemented with a unit for recording the GSR.

  • Tubes are fastened around your chest and abdomen
  • A blood pressure cuff is attached to your arm
  • Electrodes are attached to your fingers or to the palms and dorsal surface of the hands.

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