History of Polygraph

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Polygraph is actually several instruments combined into one, each component was developed independently of the others.

In 1878, science first came to the aid of the truthseeker through the research of Italian physiologist Angelo Mosso. It was then that Mosso used an instrument called a plethysmograph in his research on emotion and fear in subjects undergoing questioning and he studied the effects of these variables on their cardiovascular and respiratory activity. Mosso studied blood circulation and breathing patterns and how these changed under certain stimuli. The use of the plethysmograph revealed periodic undulations or waves in a subject’s blood pressure caused by the respiratory cycle in response to certain stimuli. Angelo Mosso was the first scientist to report on experiments in which he observed that a person’s breathing pattern changed under certain stimuli and that this change, in turn, caused variations in their blood pressure and pulse rate.

The first use of a scientific instrument designed to measure physiological responses for this purpose came in 1895 when Italian physician, psychiatrist and pioneer criminologist Cesare Lombroso modified an existing instrument called a hydrosphygmograph and used this modified device in his experiments to measure the physiological changes that occurred in a crime suspect’s blood pressure and pulse rate during a police interrogation. Lombroso is accorded the distinction of being the first person to have used the instrument successfully as a means for determining truthfulness from deception in crime suspects.


This clinical “Ink Polygraph” was invented in 1892 by Dr. James MacKensie, an English cardiologist. It recorded heartbeat, venous pulse and arterial pulse and used a clock spring mechanism to drive a paper ribbon with time markers at one-fifth a second.

In 1914, Italian psychologist Vittorio Benussi discovered a method for calculating the quotient of the inhalation to exhalation time as a means of verifying the truth and detecting deception in a subject. Using a pneumograph (a device that recorded a subject’s breathing patterns) Benussi conducted experiments regarding the respiratory symptoms of lying. He concluded that lying caused an emotional change within a subject that resulted in detectible respiratory changes that were indicative of deception.
In 1921, John A. Larson, a Canadian psychologist employed by the Berkeley Police Department, in California, developed what many consider to be the original lie detector when he added the item of respiration rate to that of blood pressure. He named his instrument the polygraph, a word derived from the Greek language meaning “many writings” since it could read several physiological responses at the same time and document these responses on a revolving drum of smoked paper. Using his polygraph, John A. Larson was the first person to continually and simultaneously measure changes in a subject’s pulse rate, blood pressure, and respiratory rate during an interrogation. His polygraph was used extensively, and with much success, in criminal investigations.

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In 1938, Leonarde Keeler further refined the polygraph when he added a third physiological measuring component for the detection of deception called the psychogalvanometer, a component that measured changes in a subject’s galvanic skin resistance during questioning, and in doing so, thus signaling the birth of the polygraph as we know it today. In 1939, Leonarde Keeler patented what is now understood as the prototype of the modern polygraph. Today, Leonarde Keeler is known as the father of polygraph.
In 1960, Cleve Backster, building upon John Reid’s Control Question Technique, developed the Backster Zone Comparison Technique (ZCT), a polygraph technique that primarily involved an alteration of the Reid question sequencing.

Backster also introduced a quantification system of chart analysis, thus making it more objective and scientific than before. This system for the numerical evaluation of the physiological data collected from the polygraph charts has been adopted as standard procedure in the polygraph field today.

Withstanding more than a century of research, development and widespread use, the polygraph test remains the most effective means of verifying the truth and detecting deception.