Duhaime's Law Dictionary

Polygraph Definition:

A lie-detector machine.

Related Terms: Penile Plethysmograph

A lie-detector machine which records even the slightest variation in blood pressure, body temperature and respiration as questions are put to, and answers elicited from a subject.

In State of Arizona v. Valdez, Justice Udall of the Supreme Court of Arizona:

"The polygraph or lie-detector is a pneumatically operated device which simultaneously records changes in a subject's blood pressure, pulse, respiration rate and depth, psychogalvanic skin reflex (skin resistance to electrical current) and, in some cases, muscular activity.

polygraph"The basis for the use of the so-called lie-detector is the hypothesis that conscious deception can be deduced from certain involuntary physiological responses in the same manner as physicians diagnose various diseases. The thesis is that lying engenders emotional disturbances which are transmuted into tangible bodily manifestations.

"The machine itself reflects and records only the subject's physiological responses to the questions propounded by the operator. He then interprets the polygraph (meaning, literally, many pictures) and determines whether the subject is lying."

The American Polygraph Association offers this definition:

"The term literally means "many writings," which refers to the manner in which selected physiological activities are simultaneously recorded. Polygraphs records respiration, cardiovascular activity and electro dermal activity of an examinee while an examiner questions the examinee. The instrument itself is a combination of several recording devices routinely used in the medical and scientific community."


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