How it works

The term “polygraph” literally means “many writings”. In 1917, the first polygraph examination was used for counterintelligence work during World War I. The FBI began using polygraph examinations in 1938. Polygraph systems and research have advanced dramatically throughout the last 70 years and in 1986 the introduction of computerized polygraph systems began which has led to today’s advanced digital state-of-the-art systems.

The name refers to the manner in which selected physiological variables are simultaneously recorded. Using specialized components, a typical polygraph collects physiological data from numerous signals generated from the human body. Respiratory activity is recorded by two convoluted rubber tubes called Pneumographs that are placed over the examinee’s chest and abdominal areas. Electrodermal or sweat gland activity is recorded by two small sensors attached to the fingers. Cardiovascular activity is recorded by a blood pressure cuff or similar device.