Lie Detector

Only available on StudyMode
  • Topic: Polygraph, Aldrich Ames, Lie detection
  • Pages : 10 (3738 words )
  • Download(s) : 60
  • Published : November 4, 2012
Open Document
Text Preview
Introduction (Polygraph)
People have always wanted to distinguish truthfulness from lying in suspects of crime. In the past, there were many techniques to find out the truth from someone. However, the techniques were based on an assumption that some physiological effect would cause recognizable symptoms that could indicate truth or lie. An example dated early in 1700s. British novelist Daniel Defoe wrote an essay in which he said that taking a pulse of a suspect was effective to distinguish truth from lies. In 1878, a researcher of Italian physiologist, Angelo Mosso, used an instrument called a plethysmograph in his research on emotion and fear in subjects during questioning. He noticed that blood circulation and breathing patterns changed under certain stimuli. In 1895, Cesare Lombroso, an Italian physician, psychiatrist and pioneer criminologist, modified an instrument called a hydrosphygmograph and used this device to measure physiological changes in a crime suspect in a police interrogation. Lombroso was the first person to use the instrument to determine truthfulness from deception. In 1906, Sir James Mackenzie, M.D., improved his clinical polygraph of 1892. Dr. Mackenzie’s improved polygraph resembled that of the modern polygraph. It was in 1921 when John A. Larson, a Canadian psychologist employed by the Berkeley Police Department in California, developed what many people considered the first polygraph. His polygraph was the first one that could continuously and simultaneously measured changes in pulse rate, blood pressure, and respiratory rate during an interrogation. Larson’s polygraph was extensively used in criminal interrogation. Nowadays, polygraphs are widely used in many areas so people will need standards for polygraph. As a result, the American Polygraph Association and the American Society for Testing and Materials have established the standards for polygraph test. With the standards, people can rely on them. Mechanism

Working Principle of Polygraph
Polygraph works using a standard on the interaction between our mind and body, which will result an interaction to the environment, for example nervous, happy, and sweating, etc. In this polygraph testing we are expecting that the suspect will feel either nervous, shock, or no reaction, etc. In consideration of the movement from the autonomic nervous system and sympathetic members of the autonomic system, the suspect will have mental and physical defense which will tell us how stress he is under the interrogation. There will be a graph that will show suspect nervous system that the examiner needs to pay attention to it, because from the graph the result will be interpreted. There are 3 systems from human body that will be analyzed. This is because if only 1 sensor, it will be quite hard to determine either the suspect is lying or telling the truth. Hence, there are 3 sensors that the examiner can combine it and analyze the result. The sensors are: 1. Pneumograph (pneumatic tubes which is assisted by chains, fastened around the chest and abdomen of the person): It will measure the suspect respiration. If the suspect’s suddenly becomes unnatural, it will be shown very clear in the graph display. 2. Galvanometer ( 2 electrodes are affixed to 2 fingers on the same hand, and a current is running through it) : It measures how many moistures in your finger ( how much you sweat) 3. Cardiograph (a blood pressure cuff that is fastened in your arm). It measures your cardio and blood pressure The examiner will analyze the result using data from these 3 sensors. If there are many unnatural fluctuations (sudden change), the examiner may conclude that the suspect is lying. When the fluctuation is normal (without sudden change) the examiner may conclude that the suspect is telling the truth There are 3 important kinds of question, which are relevant question, irrelevant question, and control question. There will be 9 – 10 questions are prepared, with 10...
tracking img