Principles of natural justice and fair play are constitutional guarantees. It can't be disturbed. What needs to be understood is that narcoanlysis will result in eliciting truth is a personal opinion. There is no exactness. Only inferences can be drawn. Therefore it is too feeble to be considered aganist anyone with evendentiary value.
Narco analysis is only help in investigation but cannot be used as evidence. whatever said by the accused during the test only helps the investigation officer to investigate the case but can bot be used as evidence against the accused. becuase no one can be permitted to violate the provision of the constitution.
Mr. Krishnan the Narco analysis test is the scientific mode of investigation and the Delhi High Court in number of judgements has referred the matter to the same. Section 53 of the Code of Criminal Procedure provides the examination of the accused by the medical practitioner at the request of the police officer. The scope of the section is enlarged by the Hon'ble High Court of Delhi and held that the Narco test is not a test of giving evidence against himself rather it is the scientific way to assist the investigating agency in decriminalization of the society.