This study provides in brief the method and historical perspective of Narcoanalysis, Polygraph & BEAP tests technique. The main aim of this study is to analyze the evidentry value, legality and Constitutional validity of Narcoanalysis, Polygraph & BEAP tests in India. The study’s emphasis is to search the nature and scope of Narcoanalysis, Polygraph & BEAP tests in the light of the Constitution of India and Cr.P.C. provisions. The paper also describes the judicial trend and analyzes the power of Court to order Narcoanalysis, Polygraph & BEAP tests technique in India. The essential feature of leading case Selvi v. State of Karnataka is presented in the paper with National Human Rights Commission guideline.