27 July 2009

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Know about Polygraph Test or Lie Detector Test

Reality Views by sm:
Know about Polygraph Test or Lie Detector Test :
From ancient times humans are using different methods to distinguish truth and lie.
Very Famous test is Agni parisha that is fire test, putting hand in the boiling pot of oil etc.
Why people lie there are many reasons but one of the most important factor is the fear of future trouble from police .or law or boss .To avoid future troubles, this fear factor makes the people lie.

The one of the early devices to find the lies was used in the year 1885 invention by Cesare Lombroso which measured changes in blood pressure which was used by the police.
Polygraph test or lie detector machine both are same and one.
It is proven fact that when a person is lying his body goes through many changes.
Using the polygraph instrument or machine it finds the changes which happens to the body person's heart rate, blood pressure, respiratory rate and electro-dermal activity (sweatiness, in this case of the fingers) change in comparison to normal levels. Fluctuations may indicate that person is being deceptive, or he is lying.
A polygraph is an instrument that simultaneously records changes in physiological processes such as heartbeat, blood pressure, and respiration.
Today there are 2 types of machines are available analog and computerized.
The test starts with the simple questions and suddenly the important question is asked it helps the person or doctor or examiner to see the bodily changes.
The theory of the polygraph test is that when people lie they get nervous about lying and fear that someone may find that the person is lying ,result is that the persons heartbeat increases, blood pressure goes up, breathing pattern changes, perspiration increases etc.
Deviation from the baseline for truthfulness is taken as sign of lying.

But as nothing is perfect this test is also not reliable many people say this test gives 90% correct results but there are other people who do not trust this type of test.
In 2007, polygraph testimony was admitted by stipulation in 19 american states.
In most European jurisdictions, polygraphs are not considered reliable evidence and are not generally used by police forces.
In Canada, the polygraph is regularly used as a forensic tool in the investigation of criminal acts and sometimes employed in the screening of employees for government organizations.
The High Court of Australia has not yet considered the admissibility of polygraph evidence.
In India recently courts have started to use and admit the test results of polygraph.