1 / 5A narco test is very different from a polygraph test, says Dr Rajkumar of the All India Institute of Medical Sciences, New Delhi. In a narco test, an injection is given to the accused. It contains sodium pentothol. Brain imaging after it enters the body via injection.2 / 5Dr Rajkumar says about what is polygraph test, your body movements can check whether a person is telling the truth or lying. This is called a lie detector test. When a person lies, there are changes in blood pressure, respiration and body temperature. 3 / 5The accused is subjected to a polygraph test before the narco test. Changes in the individual's body are first considered. Only if it is successful, further narco test can be done.4 / 5The Supreme Court had decided on these tests in the case of Selvi v. State of Karnataka and ANR. No lie detector test should be conducted without the consent of the accused. Also, test reports cannot be used as confessions. 5 / 5During the hearing of the case of DK Basu v. West Bengal, the Supreme Court had termed these trials as cruel and inhuman. Said this may violate the right to privacy.