A polygraph test, or the lie-detector test, is based on the assumption that when a person speaks lies, the physiological responses triggered in his body are different from what they would be otherwise. Cesare Lombroso, an Italian criminologist, first conducted such a test using a machine to measure changes in the blood pressure of criminal suspects during interrogation.
Methodology The accused is interrogated using instruments like cardio-cuffs or sensitive electrodes attached to his body, and variables, such as blood pressure, pulse, respiration, change in sweat gland activity, blood flow, etc., are measured. A numerical value is assigned to each response to conclude whether the person is telling the truth, is deceiving, or is uncertain.
Narcoanalysis involves injecting the accused with a drug, namely, sodium pentothal, which neutralises imagination and induces a hypnotic or sedated state such that he/she would divulge true information. The drug is said to have been used during World War II for intelligence operations.
Though a ‘softer alternative’ to torture or ‘third degree’, it helps extract the truth from suspects, it has no 100 per cent success rate.
Legal implications in India
A Supreme Court Bench had ruled in 2010 that no lie-detector tests should be administered ‘except on the basis of the consent of the accused’ after taking into consideration international norms on human rights, the right to a fair trial, and the right against self-incrimination under Article 20(3) of the Constitution. The volunteers must have access to a lawyer and have the physical, emotional, and legal implications of the test explained to them. The subject’s consent should be recorded before a judicial magistrate. The court also said that the ‘Guidelines for the Administration of Polygraph Test on an Accused’ published by the National Human Rights Commission in 2000, must be strictly followed and that the results of the tests cannot be considered to be ‘confessions’, because of the drug-induced state the subjects are in.
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