Three people accused in the NEET UG 2026 paper leak case volunteered to undergo polygraph and brain mapping tests “to establish their innocence and their non involvement” and to assist the CBI in “tracing the real culprits”.But on Monday (August 10), Special Judge (Fast Track Court) Ajay Gupta of the Rouse Avenue Court in New Delhi rejected the plea.He noted that the application at the present stage “is nothing but sheer abuse of the process of law and seems to have been filed with a view to delay the proceedings of the present case.” The CBI had also submitted before the court that their plea for undergoing the tests was not maintainable, as the chargesheet had already been filed.The order noted that since the CBI had already concluded their investigation against the accused persons, no assistance was required from them at this stage.What does the law say about lie detection tests?In the case of Selvi v State of Karnataka in 2010, the Supreme Court held that narco analysis, polygraph examination and Brain Electrical Activation Profile (BEAP) tests cannot be administered without the subject’s consent. Doing so would violate the right against self-incrimination under Article 20(3) and personal liberty under Article 21.The court there had held that these techniques seek to extract information from a person and therefore intrude upon mental privacy in a way that ordinary questioning does not. “The compulsory administration of any of these techniques is an unjustified intrusion into the mental privacy of an individual. It would also amount to ‘cruel, inhuman or degrading treatment’ with regard to the language of evolving international human rights norms,” the judgment noted.It noted that the subject undergoing the test does not consciously choose the answers that emerge, as the tests are designed to bypass the subject’s control over their own responses, which distinguishes them from a conventional interrogation or a voluntary statement.Story continues below this adIt said, “The drug-induced revelations or the substantive inferences drawn from the measurement of the subject’s physiological responses can be described as an intrusion into the subject’s mental privacy. It is also quite conceivable that a person could make an incriminating statement on being threatened with the prospective administration of any of these techniques.”Are such tests completely barred?According to Selvi, the SC permitted voluntary administration of these tests as long as the safeguards underlined in the National Human Rights Commission’s 2000 guidelines were followed.The SC held that consent for such a test must be recorded before a judicial magistrate and that the person undergoing the tests must have access to legal advice on the medical, emotional and legal consequences of undergoing such a procedure.It said, “Even when the subject has given consent to undergo any of these tests, the test results by themselves cannot be admitted as evidence because the subject does not exercise conscious control over the responses…”Story continues below this adHowever, even when these conditions are met, the SC drew distinctions between administering the test and relying on its results. As the subject is unconscious while the responses are given, the test results themselves cannot be treated as substantive evidence of guilt.It is imperative to note that Section 23 of the Bharatiya Sakshya Adhiniyam (BSA) states that confessions made to the police officer in custody cannot be used as evidence against the accused — except when such a fact leads to discovery of a physical fact.This can include an object, a location or a document that would fall under the “fact discovered” exception under Section 23 of the BSA. However, even the discovered fact functions as corroboration rather than proof of its own.Can an accused insist on voluntarily taking the tests?The SC in Amlesh Kumar v State of Bihar (2025) set aside a Patna HC order that had allowed narco-analysis on all accused and witnesses in a dowry harassment case and did so at the stage of bail.Story continues below this adThe bench of Justices Sanjay Karol and Prasanna B Varale said that at the stage of bail, the court is only required to look into the nature of the crime, allegations, period of custody and whether the accused would influence the witness, etc. It is not required for the court to enter “into a roving enquiry or accepting the use of involuntary investigative techniques.”The court also said that even when a person voluntarily requests the tests to be conducted, such a test should be examined at an appropriate stage of the trial when the accused is exercising their right to lead defence evidence. Even then, the court was clear that the permission does not follow automatically as “it cannot be said that undergoing a narco-analysis test is part of the indefeasible right to lead evidence, given its suspect nature.”The court thus retains the discretion to weigh free consent, the safeguards laid down, and whether the test is necessary on the facts of the case before permitting a test.