When a person undergoes a Lie Detector Test various parts of the machine are attached to his body by wires. The interrogator asks the person all relevant questions. The physiological changes taking place while questioning are recorded by a pen recorder fitted in the instrument. Finally these observations are analysed. However, the Polygraph is not wholly dependable. It accuracy is estimated to be about 80%. Infact a lot depends on the skill of the examiner in this regard some people who are truly unaware of the fact that they are lying, can not be caught by the Lie Detector. Moreover the hardened criminals can control their emotions and render this machines ineffective. Because of these reasons the results of a Lie Detector Test cannot be accepted as an evidence in the court of Law. However it is being used by the Police departments in almost all the countries.
