Introduction  After the decision of the Supreme Court of India all the cases of stamp scam are transferred to the CBI is using new scientific techniques like polygraph test or Narco-Analysis test to interrogate the accused person. This article focuses on the constitutional validity of such tests particularly Narco Analysis test Sec. 2(h) of the CR.P.C. Defines ‘Investigation’  ‘Investigation’ includes all the proceedings under this Code for the collection of evidence collected by police officer or by any person (other than Magistrate) who is authorized by a Magistrate in this behalf; It appears from the definition that every thing, which is authorized by the Cr.P.C., is within the meaning of the term ‘investigation’. The question which comes for consideration that whether there are any limitations on the police officer investigating a case? What police can do while i ....