A polygraph test can also be described as a “lie detector test” (although the more accurate term would be the “truth verifier), and is usually used as a mechanism of verifying whether somebody is lying or telling the truth by evaluating the subject’s physical conditions during the process. This method is very reliable, provided it is handled and administered correctly, and is used in many instances.


The First Stage

The polygraph test can be carried out by a private investigator or a qualified professional polygraph examiner. It usually takes two hours or less, the first stage taking the longest – up to an hour and sometimes even longer. The first stage takes that much time, because the examiner always takes his or her time to explain to the subject how the polygraph works and to develop the relevant questions properly. The more the subject knows about the procedure, the less nervous they are and the more accurate the test results are. The explanation involves outlining all of the equipment used and its functions, the physiological responses measured that indicate stress associated with lying, and the way the results are read and evaluated in the final stage of the procedure.


The Second Stage

Is the actual questioning, during which the subject is connected to the machine. The components attached to the subject that connect him or her to the instruments are the two tubes called pnuemograph tubes placed on the subject’s chest, the two finger plates placed on the subject’s hands, and the cardiosphygmograph placed on the subject’s arm. There is no specific dress code required for this procedure, -although short sleeves are preferable – blood pressure is an important physiological response measured during the test by the cardiosphygmograph. Heart rate and breath rate are also measured, with the help of the pnuemograph, not dissimilar to how the doctors do it. Galvanic Skin response, or GSR, is also very important. It changes due to the sweat glands’ activity which occurs when a person is stressing out by lying, and the machine traces these changes with the help of the finger plates to determine if the subject is telling the truth.

The questions that are going to be asked during the examination are all constructed and agreed upon during the first stage of the procedure and the subject’s consent is required prior to asking them. There can only be “Yes” or “No” questions asked during the polygraph test. That way, the results are more reliable and accurate.


The Final Stage

Comes after the subject answers all the questions and involves the private investigator or the professional polygraph examiner analysing the results and making a decision as to whether the subject was lying or telling the truth during the questioning.