The polygraph these days is in an evolution of what and how it was at the start of the 20th century. In its most basic form, lie detection test was practiced in China and India where people used the grains of rice as lie detectors. The subjected liars would have to be asked to chew the grains of rice. If the person lied, the chewed uncooked rice would be spat out dry because they considered a liar to be a dry mouth.
This unscientific way of detecting deception through the “spitting method” led to the invention of the polygraph. The polygraph may be more scientific than the spitting method but the determination of the reliability of the test results are of the same degree.
The spitting method has its basis of what constituted a liar. The modern polygraphs, still rely on the notion that the psychological act of telling a fib will carry with it tell-tale psychophysiological signs. These include changes in heart rate and blood pressure, altered breathing patterns and increased sweating. This is based on the assumption that human beings manifest changes in the three body systems being monitored all throughout the duration of the test.
The invention of the polygraph has to a considerable extent taken a big leap from the time lie detection was in its rude form. American John Larson, who worked for the police but also had a biology degree, is considered by many to be the inventor of the modern device. His polygraph, which tested blood pressure, was used at the Berkeley Police Department in California from 1921. The invention of Larson was later improved on by other inventors in the years that followed. Such improvement included testing of respiration and perspiration.
The successful conduct of the polygraph test lends itself to the manner in which examiners administer the test. Examiners nowadays are more competitive and stricter in terms of test administration. It has to be noted that there are rules that have to be observed in the conduct of the test. The pre-test routines have to be carried out properly. And examiners of today are more than ready to assume their responsibility.
Present – Day Polygraphs
Today, polygraphs boast of the infusion of a computerized system to the instrument. Many US police departments have dedicated polygraph units, using them to help narrow the field of suspects and focus on those who have failed the test. US police agencies believe in the important role polygraphs play in conducting successful investigations.
Potential Damage of the 96% Accuracy
Despite the considerable advances in polygraphs, there still remains so much doubt about the accuracy of polygraphs. One famous “failure” associated with polygraph testing was Gary Ridgway, the Green River killer who was responsible for up to 71 deaths in the US. He passed a polygraph after each of his vicious and horrific crimes. This is the potential damage of the 4% discrepancy on the accuracy of polygraphs.