Movies which are often followed by silent and pensive strolls on the way back home, are often thought-provoking. You must have had this experience after watching Talwar which really psyched up each one of us with the fix of Talwar parents. Those who had seen this movie, might recall the narco test which had almost got the CBI to wring confession of the crime by the suspected persons. But the results post the narco test were not considered as valid evidence in the court of law. The story here is not about murder case or about narco test. This small tale is reminiscent of an instrument called polygraph which is able to disgorge truth from the lairs and could be of crucial use in investigations but lacks evidentiary value.
Commonly known as lie detector, a polygraph is a combination of polygram connected to a screen which records changes in four important vectors viz. Respiration rate, pulse rate, blood pressure and skin resistance. These physiological changes are found in the person who tries to distort truth or is lying. The polygraph which is a coordination of science and psychology, was invented by John Larson at Berkeley, California in 1921. He improvised on the lie detector test developed by William Moulton Marston, which could point out the lie by the deviations in blood pressure.
It was found that when a person is lying, his or her blood pressure races up. The physiological changes occurring in the person can to an extent evince the possibility nabbing the culprit. Usually the person who speaks lie, has the fear of being grabbed which creates mental excitation, as a result of which the adrenalin gland is stimulated. This triggered gland secretes adrenaline hormone which fuses with blood stream and raise the pulse rate, the respiration rate and blood pressure of the person getting examined. The skin resistance or Galvanic Skin Response (GSR) is also indicative of a person’s veracity. The person who lies usually sweats more than usual, which leaves the negatively charged chloride ions on the surface of the skin.
This lowers the resistance of the body and when a tiny electric current is sent into the body, the galvanometer records the current on the monitoring screen. Lie detectors or polygraphs have proved to be of much importance where the investigations are complicated and there is a need to fast track the case. Polygraph based evidence are not admissible in many courts of law. On one hand there is a need to expedite the investigations and on the other hand the info based on such test is deemed all out of whack. The problem remains unresolved.
However there are bodies London Polygraph which claim to provide accurate, scientific and state-of-art lie detector services. http://londonpolygraph.co.uk/ can be used to view the services provided by them. The scientific techniques and deft examiners provided by them make the entire procedure and results indubitable. They record different kinds of psychological changes in the most structured manner and help in determination of truth.