From the Examiner: How does polygraph work?
Polygraph, also known as a lie detector examination, is a medico-logical process of collecting data from the human body. Generally, there are three components associated with the protocol: the first is a set of two convoluted tubes placed on the chest and stomach of the examinee. These components monitor respiration behavior. The second component is comprised of either metal plates or sticky pads which are attached to the fingers looking for activation of sweat gland activities. The third component is a blood pressure cuff placed on the arm, usually the left, which is inflated during the examination and held steady while monitoring relative blood volume and relative blood pressure.
A polygraph examiner then looks for any natural changes that occur within the body which effect these three monitored areas of bodily reaction. The autonomic response is the key and occurs when the body attempts to defend itself during cognitive dissonance in the development of lies. This is similar to the feeling you get when you are driving and enter a radar zone where police are monitoring you. Once all test questions are asked and answers are provided, a polygraph examiner will compare the reactions to the various types of questions looking for any consistent significant reactions to the relevant test questions. These reactions are subsequently evaluated and assigned a numerical value, and based on researched cutoff scores, a score of pass or fail is assigned. An effective lie detector test requires the examiner to ask the right questions, collect the right data, and make the right observations in a controlled, distraction-free environment.
Note of Caution
Your test is important! Private examiner prices vary. Often the old adage, "You get what you pay for" applies. Before hiring an examiner, check and verify his or her qualifications.