Lie Detection Techniques: Polygraphy

Lie Detection Techniques

• Polygraphy: a process of detecting deception using a polygraph machine, which measures changes in blood pressure, pulse, respiration, and skin resistance as indicators of emotional disturbance, particularly lying.
• Polygraph: a sensor-equipped device that tracks and measures physical changes associated with the vegetative nervous system.

Historical Background of Lie Detection Techniques

• Luigi Galvani (1791): introduced the galvanic skin reflex (GSR), which measures the electrical resistance of the body, expressed in ohms.
• Cesare Lombroso (1836-1909): developed the hydro sphygmograph, the first scientific equipment for detecting deception, which measured variations in pulse and blood pressure.
• Francis Galton (1879): created the word association test, a psychological test in which the patient is given a group of words that are sufficiently separated in time for the patient to say their first idea formed from each word.
• Angelo Mosso (1895): researched the impact of fear on the cardiovascular system, serving as the basis for techniques used to detect lies.
• Otto Veraguth (1907): used the technique of word association with a galvanometer, inventing the term "psychogalvanic reflex" (later changed to electrodermal response).
• Vittorio Benussi (1914): introduced the pneumograph to detect deception, a device that depicts inhalation graphically.
• William Moulton Marston (1915): experimented with the sphygmomanometer, conducting research on its ability to detect lies, earning him the title "Father of Modern Polygraphy".
• Harold Burtt (1918): found that changes in systolic blood pressure were more effective than changes in breathing in detecting deception.
• John Larson (1921): developed a device that continuously and simultaneously measures blood pressure, pulse, and respiration.

Historical Methods of Lie Detection

• Wager of Battle: a medieval method where the judgment of God was thought to determine the winner, with the defeated party allowed to live as a recreant.
• Ordeal by Balance: used in ancient India, where the accused was placed on one side of a scale, and if they were found lighter, they were acquitted.
• Ordeal by Rice Chewing: an ancient Indian method where the person on trial eats a specific type of rice, and if saliva is mixed with blood or the corner of their mouth swells, they are declared a liar.
• Boiling Water Ordeal: a medieval method where the accused had to lift a stone out of boiling water; if they succeeded, they were considered innocent.

Observation Methods

• Non-verbal clues:
  • Deep breathing
  • Blushing, paling, or profuse sweating of the forehead
  • Rolling of eyeballs
  • Dilation of the eyes
  • Protusion of eyeballs and elevation of upper eyelids
  • Fidgeting, tapping, or drumming of fingers on the chair or other surfaces
  • Squinting and excessive winking of the eyes
  • Twitching of the lips
  • Unnecessary movements of the hands and feet
  • Failure to look the inquirer
  • Pulsation of the carotid artery in the neck
  • Excessive activity of the Adam's apple
  • Incoherence, trembling, and sweating of the whole body
• Verbal clues:
  • Vague answers
  • Laughing it off
  • Exaggerated honesty
  • Sympathy
  • Answering a question with a question

The Human Body System: Nervous System

• Receives, evaluates, integrates, and stores input from the environment via the brain and nerve tissues.
• Sends messages to various parts and organs for a specific reaction.
• The central nervous system (CNS) consists of the brain and spinal cord.
• The peripheral nervous system includes sensory neurons, motor neurons, somatic nervous system, and autonomic nervous system.