Interesting Facts about Polygraphs


  Interesting Facts about Polygraphs

After reading the EOTO post about polygraph tests, I learned some interesting facts. Polygraphs were originally used starting in1892 as medical devices to measure irregular heart rhythms.

In 1895, Lombroso modified the machine so it could measure physiological changes in the pulses of suspects being questioned by the police. 


The basic form of the polygraph came about in 1915 and the modern polygraph in the year 1921. 

It was able to measure several different physiological responses including heart rate, blood pressure and respiration. 


In 1939 Keller patented what we know as the modern polygraph and in 1993 statisticians were able to create a mathematical algorithm to better interpret the results so they could understand what results indicated that a suspect is lying. 


Interestingly, a polygraph does not detect lies, it detects responses linked to stress and anxiety. 

Because many people think that a polygraph can detect dishonesty, some suspects will even admit to the crime before even taking the polygraph! 

 

Additionally, since polygraphs are not really detecting lies, innocent people may be in trouble when they are just nervous or scared because their physiological responses are the same as if they were lying, while deceptive people can also remain calm so there are no physiological changes when they are questioned.


We are led to believe that polygraphs are trusted because of what we see on television, but polygraphs are not admissible in most courts so they cannot be used as definitive proof of a crime.


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