Polygraph Facts

The Problem

Deception has been a problem facing mankind for thousands of years. Lying is such an issue that God addresses the problem of lying to Moses. When providing the 10 commandments to Moses, in Exodus 20:16 God says "Thou shall not bear false witnesses against thy neighbor".

In 1 Kings 3:16 - 27 King Solomon is confronted with the dilemma of two women both claiming to be the mother of one child. After listening to the women, the king said, "Bring me my sword "Divide the living child in two, and give half to the one, and half to the other." Upon hearing of King Solomon's solution, the first woman said to King Solomon "oh, my lord, give her the living child, and by no means slay it." But the second woman said, "It shall be neither mine nor yours, divide it". The king answered and said, "Give the living child to the first woman and by no means slay it; she is the mother."

As the history of mankind is reviewed, you realize that some people feel compelled to deviate from the truth. Why do people lie? Often people lie because they do not wish to cause disappointment to a child or a loved one. Is it proper to lie in this situation, probably not, but people justifying this type of lying say it is because of love and respect, not wishing to inflict pain.

Many who veil the truth do so for malicious reasons. There are people who tell lies hoping to cause embarrassment or pain for others. Some people lie because of their inadequacies, either real or perceived. There are those who "need" to lie, circumstance has required them to deviate from the truth out of fear, fear of the truth.

Few people possess wisdom to the same degree that King Solomon did. Confronted with this problem since antiquity, man has made several attempts to overcome the problem. Today, young men entering Boy Scouts are taught the Scout Law. The very first point cited in the law is "A Scout is Trustworthy" boys are told how to deal fairly and honestly with people. Young women who become Girl Scouts learn the Girl Scout Law. The first tenet taught is:" I will do my best to be honest and fair," It is unfortunate, but not all people choose to be honest and fair in their dealings with others.

Man has been confronted with determining veracity of individuals in many different instances. Lacking the wisdom of Solomon, man has attempted for years to devise a method that would enable him to make sound decisions when deception may be involved.

Circa 1895 Caesar Lombroso, a physician, psychiatrist, a pioneer criminologist the man recognized by many as the father of criminology. Lombroso began using a hydrosphygmograph to detect deception. Although not the inventor of the hydrosphygmograph, he should be considered the first person for using it to detect lies.

Dr. Hugo Munsterberg, Ph.D., M.D., of Harvard University, discussed in his 1908 book, On the Witness Stand, the physiological tracking of blood pressure, respiration, and galvanic skin reflex. He stated physiology could be utilized to assist in the detection of deception.

A student of Dr. Munsterberg's, William M. Marston was awarded the Medal of Freedom by the government of the United States for his work in detecting German spies during the first World War. Marston used systolic blood pressure symptoms, using a blood pressure cuff, sphymomanometer and discontinuous blood pressure reading.

Dr. John A. Larson developed what many consider to be the first modern day polygraph instrument, circa 1921. Later Leonard Keeler would further refine this instrumentation.

The Solution

Polygraph: A scientific instrument used for the detection of deception. A device capable of producing recordings of physiological phenomena, (breathing, galvanic skin resistance, and cardio tracing) that may be used as the basis for the application of a reliable technique for diagnosing truth or deception.

Polygraphs record Physiological phenomena, respiration, galvanic skin response, and cardiac activities.

Respiration, the word respiration means "one inspiration, plus one expiration". A healthy adult has an average of 12 cycles per minute.

Galvanic Skin Response, "a reaction to certain stimuli as indicated by a change in the electrical resistance of the skin".

The galvanometer is basis for the galvanic skin response tracings recorded by a polygraph. Galvanometers are also used in many diagnostic instruments, such a electrocardiographs.

Cardiac Activity increases and decreases in blood pressure, change of heartbeat, movement of the dicrotic notch.

"Blood pressure (BP) refers to the pressure in arteries exerted by the left ventricle when it undergoes systole and the pressure remaining in the arteries when the ventricle is in diastole".

Factors effecting the heartbeat are emotion, exercise, hormones, temperature, pain, and stress. "The normal number of pulse beats per minute is the average adult varies from 60 to 80, with fluctuation occurring with exercise, injury, illness, and emotional reactions".

Movement of the dicrotic notch is caused by the rushing of blood against closed semi lunar valve of the heart.

The Central Nervous System (CNS) is generally considered to be the brain and spinal cord. The CNS regularly receives input from the peripheral nervous system, which has an afferent division and an efferent division.

"The afferent division includes somatic sensory nerve cells, which carry impulses to the central nervous system from receptors located in the skin, the fascia, and around the joints, and visceral sensory nerve cells, which carry impulses from the viscera of the body to the CNS.

The efferent division a subsystem of the peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system:

  1. The somatic nervous system is also the voluntary nervous system because its motor functions may be consciously controlled. It includes somatic motor nerve cells, which carry impulses from the CNS to the skeletal muscles. The impulses carried by the somatic motor nerves produce contractions of the skeletal muscles. Muscle contractions that are brought about by the somatic nervous system may be reflex responses; they may not be consciously controlled.
  2. The autonomic nervous system - or involuntary nervous system - in contrast to the somatic nervous system, is composed of visceral motor nerve cells, which transmit impulses to smooth muscles, cardiac muscle, and glands. Visceral motor impulses generally cannot be consciously controlled.

The autonomic nervous system may be subdivided functionally into sympathetic and parasympathetic divisions; "...which are actually overlapping divisions".

Generally the parasympathetic nervous system is responsible for regulating the body during periods of low stress, uneventful times, times of calm and relaxation. While the parasympathetic nervous system decreases heart rate and promotes digestive functions, the sympathetic nervous system takes charge during times of high stress. The sympathetic nervous system increases heart, and breathing rates. It helps us respond when we are called upon to perform a physical feat; such as running to get away from something threatening us or standing and confronting a threat to our welfare, or well being. Many times people refer to this reaction as "fight or flight."

"Laboratory test can also be used to identify psychogenic disorders. There is an intimate relationship between emotional and physiological functioning. When a person's hostility level rises, so may the blood pressure, When a person's anxiety level rises, so may the activation level of the sweat glands. Such changes can be monitored by physiological recording devices such as a polygraph," a instrument "equipped with sensors, which, when attached to the body, can pick up subtle physiological changes. These fluctuations, in the form of electrical impulses, are amplified within the polygraph and activate pens that then record the changes on a continuously moving roll of paper"(*). "When sensors are attached to the scalp the result is an EEG, electroencephalogram. When the sensor measures changes in the electrical resistance to the skin, the result is a reading of galvanic skin response (GSR). When the sensor is used to pick up subtle changes in the electrical activity of muscles, the result is an electromyogram (EMG). The polygraph can also measure a number of other physiological responses such as heart rate," "and blood pressure."

Polygraph Today

Since the days of Caesar Lombroso, Dr. Hugo Munsterberg, and Dr. John Larson the detection of deception, polygraphs instrumentation, and polygraph techniques have improved dramatically. Today a polygraph may be either a conventional analog polygraph instrument, or a computer assisted polygraph instrument.

Who uses the polygraph? The Department of Defense and its' many investigative agencies of the, Army, Navy, Marines and Air Force. The National Security Agency, the Central Intelligence Agency, United States Secret Service, Federal Bureau of Investigation, Internal Revenue Service, Drug Enforcement Administration and numerous other intelligence and federal law enforcement agencies.

In Indiana polygraph is used extensively within the law enforcement community. The Indiana State Police, Warsaw Police, Allen County Police Department, Lafayette Police, DeKalb County Sheriff, Indianapolis Police Department, Madison Police, and the Marion County Sheriff, these are but a few of the agencies utilizing this extremely valuable investigative instrument.


Polygraph is extremely accurate, American Polygraph Association states that polygraph is between 85% and 95% accurate. The are studies that have been conducted which suggests accuracy to be greater than 95%

J. Widacki and F. Horvath, published in the Journal of Forensic Sciences Vol. 23, No. 3, pages 596 - 601, July 1978 In this article, the researchers assess the utility/validity of the polygraph technique in comparison to fingerprint identification, handwriting analysis, and eyewitness identification:

Polygraph - 95%
Handwriting - 94%
Eyewitness - 64%
Fingerprints - 100%

Reported In a field study conducted by Honts and Raskin in 1988 reported accuracy was:
Innocent - 100%
Guilty - 92%
Combined Average 96%

Other studies and results:

Truthful and Deceptive Results Compared:






# Tested


# Tested




































  • Weighted Average: 95.8%
  • Range: 82.2 - 100%


  • Weighted Average: 89.3%
  • Range: 75 - 100%

Court Admissibility

Admissibility varies from state to state and jurisdiction to jurisdiction, generally in Indiana polygraph evidence is only admissible under stipulation. A stipulation is a legal document prepared and agreed to by attorney's for both the defense and the prosecution. Admissibility is always however at the discretion of the court. Different rules of evidence apply for the federal and state courts.

Gerard J. Tortora & Nicholas P. Anagnostakos, Principles of Anatomy and Physiology 5th ed., New York, 1987: 570
Mosby's Medical, Nursing & Allied Health Dictionary 5th ed, St. Louis, 1998: 671.
Gerard J. Tortora & Nicholas P. Anagnostakos, Principles of Anatomy and Physiology 5th ed., New York, 1987:497.
Mosby's Medical Nursing & Allied Health Dictionary 5th ed., St. Louis, 1998, 1357.
Alexander P. Spence, Basic Human Anatomy, 3rd ed., Redwood City, 1990: 349 - 351.
Richard R. Bootzin, Joan Ross Acoella, Lauren B. Alloy, Abnormal Psychology, Current Perspectives, 6th ed., New York, 1993: 147.
U.S. Department of Defense Polygraph Institute