lie detectorSince the dawn of civilization, mankind has sought ways to distinguish the truth from the lies in those individuals suspected of wrongdoing. Various inventive techniques have been tried over the centuries, many of these being ridiculous and cruel. Despite their primitiveness, each technique was based on the assumption that some form of physiological reaction occurred within a person when confronted with certain stimuli regarding a specific event. This physiological reaction would, in turn, be manifested in certain recognizable symptoms that were indicative of either honesty or deception.

In 1878, science first came to the aid of the truth seeker through the research of Italian physiologist Angelo Mosso. It was then that Mosso used an instrument called a plethysmograph in his research on emotions and fears in subjects undergoing questioning. He studied the effects of these variables on their cardiovascular and respiratory activity. Mosso studied blood circulation and breathing patterns, particularly how these changed under certain stimuli.

Until the end of the 19th century, no measuring device for the detection of deception had ever been used. 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's early device for measuring pulse rate and blood pressure is similar to the cardiosphygmograph component of the contemporary polygraph. Although he did not invent the hydrosphygmograph, Cesare Lombroso was accorded the distinction of being the first person to have successfully used the instrument as a means for distinguishing truthfulness from deception in crime suspects. On several occasions, he used the hydrosphygmograph in actual cases to assist police investigations.

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 signs 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 1915, Dr. William Marston, an American attorney and psychologist, is credited with inventing an early form of the lie detector when he developed the discontinuous systolic blood pressure test. This would later become one component of the modern polygraph. Dr. Marston's technique used a standard blood pressure cuff and a stethoscope to take intermittent systolic blood pressure readings of a suspect during questioning for the purpose of detecting deception.

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polygraph instrumentIn 1921, John A. Larson, a Canadian psychologist employed by the Berkeley Police Department, in California, developed what many consider to be the original modern polygraph instrument 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.

In 1925, Leonarde Keeler, who had gained firsthand experience in polygraph interrogations while working with John A. Larson at the Berkeley Police Department, worked to create a less cumbersome polygraph instrument that used inked pens to record the relative changes in a subject's blood pressure, pulse rate and respiratory patterns.

In 1938, Leonarde Keeler further refined the instrument when he added a third physiological measuring component for the detection of deception — the psycho galvanometer: a component that measured, during questioning, changes in a subject's skin electrical resistance. In doing so, it signalled the birth of the polygraph as we know it today.

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polygraph techniqueBetween 1945 and 1947, John E. Reid, a lawyer from Chicago, Illinois, developed the Control Question Technique (CQT), a polygraph technique that included control questions (comparison) which were designed to be emotionally arousing for non-deceptive subjects and less emotionally arousing for deceptive subjects than the relevant questions previously used. The Reid Control Question Technique was a major breakthrough in polygraph methodology. Additionally, John E. Reid was the first examiner to use movement sensors to detect in any movement during an examination.

In 1948, Leonarde Keeler founded the world's first polygraph school — the Keeler Polygraph Institute — in Chicago, Illinois.

In 1958, Cleve Backster, an ex-polygraph examiner with the CIA, introduced a quantification system of chart analysis, thus making it more objective and reliable. 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.

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polygraph examinationDuring the 1980s, research was conducted on computerized polygraph at the University of Utah by Drs. John C. Kircher and David C. Raskin developed the Computer Assisted Polygraph System (CAPS), which incorporated the first algorithm to be used for evaluating physiological data collected for diagnostic purposes. In 1992, the polygraph made its official entrance into the computer age.

In 2003, the U.S. Department of Energy commissioned a review committee of The National Academy of Sciences to study the scientific evidence on the polygraph. In this endeavour, the committee sifted through existing evidence in the polygraph research literature and did not conduct any new laboratory or field research on polygraph testing for, as they clearly reported, real-world conditions are difficult — if not impossible — to replicate in a mock-crime setting or a laboratory environment for the purpose of assessing polygraph effectiveness.

The review committee of The National Academy of Sciences concluded that, although there may be alternative techniques, none can outperform the polygraph nor do any of these yet show promise of supplanting the polygraph in the near future.

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

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Polygraphist expert, Sergeant Michel Côté has spent over twenty years in the fields of policing, investigations, intelligence and military operations