Constitutional Validity of Scientific Interrogation Techniques in India: An Analysis of Narco-Analysis, Polygraph and Brain Mapping Tests

Narco-analysis, often described as a “truth serum” technique, has emerged as a controversial tool in criminal investigations, particularly in India. This study critically examines the scientific validity, legal permissibility, and constitutional implications of narco-analysis within the framework of Indian criminal jurisprudence. While projected as a modern alternative to coercive interrogation methods, narco-analysis raises serious concerns regarding reliability, voluntariness, and the protection of fundamental rights. The research traces the historical evolution and pharmacological basis of narco-analysis, highlighting its inherent limitations, including suggestibility, hallucinations, and the risk of false or distorted responses. It further analyzes the doctrine of self-incrimination under Article 20(3) of the Constitution of India, along with the closely related rights to silence and privacy under Article 21. Judicial interpretations, particularly in Selvi v. State of Karnataka, have been examined to establish that involuntary administration of such techniques constitutes testimonial compulsion and violates personal liberty. The study also evaluates the evidentiary inadmissibility of statements obtained through narco-analysis under the Indian Evidence Act, 1872, while addressing the limited and controversial scope of derivative use under Section 27. A comparative analysis of legal positions in jurisdictions such as the United States and the United Kingdom further reinforces the global reluctance to accept such techniques due to their coercive and unreliable nature. Ultimately, the research concludes that narco-analysis, despite its perceived investigative utility, is incompatible with constitutional safeguards, scientific standards, and principles of fair trial. It advocates for stricter legal regulation, enhanced reliance on conventional forensic methods, and the prioritization of human rights in criminal investigations.