Polygraph Test: How It Is Done and Its Reliability

Lie detection has been a tough job for crime detection agencies because of higher chances of deception involved by the guilty. Also there are skeptic theories surrounding it that it is not an exact science. It is also called Polygraph test which is largely used in the USA and is very popular all over the world. It has ousted all the controversies and has been successful in detecting crimes, frauds, thefts and resolving personal relationship issues.

How does it work?

It might feel strange if an electronic machine, which works with the help of human brain, can really make out lie told by examinee. It is indeed humorous to many. However, some experts opine that Lie detector test gets grip of the psychological changes that the body goes through while lying. You seem to sweat a lot, your heartbeat starts racing and blood pressure tends to climb up showing inadvertent signs of anxiety. Adding to this there are levels of testing in this like Stimulation test and high level tension tests which pull out any hidden answers if the examinee behaves to be over smart. The physiological indices are the benchmarks for measurement of accuracy here and any sign of sidetracking the facts can be easily detected. 

Components of Polygraph:

In this test there are three main devices which are influential in grasping the physiological changes in the body while during the test. They are:

Cardio spygmograph: This device comes with a blood pressure belt worn around the examinee's hand. When the test is happening, the blood pressure keeps rising. There is a typical sound that the examiner can hear when the blood flows in the examinee's veins. The resultant sound is amplified and the obtained magnitude is measured as blood pressure while the highs and lows of the sound is used to measure heart rate. 

Pneumograph: The respiratory levels of the examinee are measured with the help of this device. Some individuals tend to have shortness of breath when in anxiety which is all recorded with the means of two air filled tubes one placed around the examinee's chest and another around the abdomen. The breathing patterns during inhalation are recorded by Polygraph which shows fluctuations in the air pressure. 

Galvanograph: Sweating is a common symptom of panic. Galvanograph aims at measuring Perspiration which is exerted during questioning with the help of electrical sensors affixed to finger tips the skin of which is considered to be having maximum sweat glands. The more the amount of sweat the less electrical current will be measured. But this method is not considered so productive when compared to the other two.

Where is it used? It is tremendously successful in the fields of crime investigation, robberies and even in personal relationships in the USA and in many other countries.

Criticisms apart, Lie detection test, when undertaken by an experienced professional and modern equipment used, can provide 75% to 95% accuracy. The examiner should be strong enough to analyze the truthfulness of the examinee.
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