In a major blow to investigating agencies, the Supreme Court on Wednesday held unconstitutional and violation of the ‘right to privacy' the use of narco analysis, brain-mapping and polygraph tests on accused, suspects and witnesses without their consent.

A three-Judge Bench of Chief Justice K.G. Balakrishnan and Justices R.V. Raveendran and J.M. Panchal, in a 251-page judgment, said: “We hold that no individual should be forcibly subjected to any of the techniques in question, whether in the context of investigation in criminal cases or otherwise. Doing so would amount to an unwarranted intrusion into personal liberty.”

The judges said: “The compulsory administration of the impugned techniques violates the right against self-incrimination. The test results cannot be admitted in evidence if they have been obtained through the use of compulsion. Article 20 (3) of the Constitution [No person accused of any offence shall be compelled to be a witness against himself] protects an individual's choice between speaking and remaining silent, irrespective of whether the subsequent testimony proves to be inculpatory or exculpatory.”

The Bench said: “Article 20 (3) aims to prevent the forcible conveyance of personal knowledge that is relevant to the facts in issue. The results obtained from each of the impugned tests bear a testimonial character and they cannot be categorised as material evidence.”

Narco analysis technique involves the intravenous administration of sodium pentothal, a drug which lowers inhibitions on part of the subject and induces the person to talk freely. The other two techniques measure changes in aspects such as respiration, blood pressure, blood flow, pulse and galvanic skin resistance. The truthfulness or falsity on part of the subject is assessed by relying on the records of the physiological responses.

Legality examined

The Bench, in a batch of appeals and petitions, examined the legality in the administration of these scientific techniques.

Writing the judgment, the CJI said: “It is our considered opinion that subjecting a person to the impugned techniques in an involuntary manner violates the prescribed boundaries of privacy.” Forcible interference with a person's mental processes is not provided for under any statute and it most certainly comes into conflict with the right against self-incrimination.

The results obtained through the involuntary administration of either of these tests come within the scope of ‘testimonial compulsion,' thereby attracting the protective shield of Article 20 (3).

The Bench held that if these techniques were used compulsorily if would violate Article 20 (3).

The Bench made it clear that even when the subject had given consent to undergo any of these tests, the test results by themselves could not be admitted as evidence because “the subject does not exercise conscious control over the responses during the administration of the test. However, any information or material that is subsequently discovered with the help of voluntary administered test results can be admitted, in accordance with Section 27 of the Evidence Act.”

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