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Sunday, September 6, 2020

A Short History of the Polygraph

      The polygraph was invented in 1921 by Dr. John Larsen, a 27-year-old University of California Berkeley medical student with a Ph.D. in physiology. Dr. Larson worked as a part-time police officer at the Berkeley Police Department under Chief August Vollmer. Larson had read a 1908 book called On The Witness Stand by the Harvard psychiatrist, Hugo Munsterberg who had been searching for a method of scientific lie detection since the turn of the century.

     In his chapter "The Traces of the Emotion," Dr. Munsterberg wrote that three physiological events take place whenever a person lies. First, the liar's blood pressure and heart beat increase; second, there are respiratory alterations; and third, telling a lie changes the person's galvanic skin response, or GSR. To measure GSR, Dr. Munsterberg used a galvanometer that picked-up variations in the body's resistance to electricity. (Munsterberg found that when the brain is excited emotionally, the individual's sweat glands alter the body's resistance to electricity.)

     In 1921, Chief Vollmer asked his "college cop" to fashion a lie detection instrument detectives could use to detect deception in the people they interrogate. After working several weeks on the project, Dr. Larson informed Vollmer that he had rigged an apparatus that could detect truth and deception, an instrument he called the polygraph.

     The cumbersome tangle of rubber hoses, wires, and glass tubing was five feet long, two and a half feet high, and weighed thirty pounds. The device could be taken apart and moved from one place to another, but it took an hour to set up.

     Larson's instrument advanced Munsterberg's technique in four ways. The polygraph recorded the physiological responses on a continuous graph while the subject was being questioned. This was an improvement over the technique of asking a question, then taking the examinee's blood pressure. The second advantage involved the ability to adjust the instrument in order to control such variables as high blood pressure or extreme nervousness. Larson's invention also produced a tangible and permanent record of test results that could be later analyzed by other experts. And finally the polygraph detected and recorded the subject's breathing patterns in addition to blood pressure and pulse rate.

     In the spring of 1921, John Larson tested the polygraph on Chief Vollmer and members of the Berkeley Police Department. The results of these experiments convinced Vollmer that Larson had invented a device that would revolutionize the art and science of criminal investigation. Larson, as the department's polygraph examiner, began using the instrument to solve a series of petty theft cases at the University of California.

     Today, for a polygraph result to be accurate, the instrument (vastly more sophisticated than Larson's invention), has to be in good working order. Moreover, the examiner must be properly trained and experienced in question formation and line chart interpretation. (Police polygraph examiners have to fight against their own bias.) Subjects have to be willing participants in the process, not under the influence of drugs or alcohol, be obese, retarded, or mentally ill. People who are very old or under fourteen do not make reliable polygraph subjects.
     In 1988 the U.S. Congress passed a law making it illegal for private employers to use the polygraph as a pre-employment screening device. Police departments and federal law enforcement agencies, however, can use the polygraph for this purpose. No court in the country will allow the admission of polygraph results as evidence of defendants' guilt. On the other hand, defense attorneys can use polygraph findings as evidence of innocence.  

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