Selvi V/s. State Of Karnataka: A Test Of Constitutional Validity

Author: Nikhilesh Koundinya Symbiosis Law School, Pune


In the landmark judgement of Selvi v State of Karnataka[1] the Supreme court held that tools of interrogation such as Polygraph test, Brain Mapping and Narco analysis are an inadmissible form of evidence because they play with the mind of the person and violate his right to privacy as an individual. It also held that such practices lead to a person self-incriminating himself which was prohibited in the Constitution. It concluded by saying that such tools are invasive theories and are harmful to the person. In this blog, we will be analyzing the court’s judgements basis constitution and evidence law.


In 2004 Selvi and others instituted the first batch of criminal appeals which were followed up by further appeals in the year 2005, 2006, 2007, and 2010. The main contention put forward by them was that the tools of interrogation being used are against the consent of the accused. The opposition contended that such tools were necessary because they led to conclusive evidence of proving the crime. Such theories lead to the person speaking the truth in a semi-conscious state which helped fasten the investigation and leading to more criminals being punished. Before we go into the analysis of the case, we must understand the working of these tools.


In polygraph tests, it is presumed that when the suspect is asked a series of questions and he answers wrongly it will produce a distinctive physiological measurement. The machine measures changes caused to blood pressure, pulse, respiration, etc. There are ways a person’s words can be misrepresented in a polygraph test:

False-positive– the response by a truthful person is said to be false.

False-negative– the response by a deceptive person is said to be true.

Hence, the practice of polygraph test is always held to be controversial. In the case of United States v Scheffer[2] case, the practice of polygraph test has been held to be unreliable. In the case of Phillion v R[3] the Supreme Court of Canada held that the results of a lie-detector test are inadmissible. Following that, in the case of R v Beland[4] they rejected the use of polygraph tests as evidence in court.


When a person lies, he uses his imagination. In this test, the person’s imagination is neutralized by making him semi-conscious. In this case, the person cannot lie and also his answers are spontaneous hence they are believed to be true. In the case of Townsend v Sain[5] the court held that the evidence is inadmissible if it is adduced by police questioning during a period when the person will be overborne by the drug.

The court in State v Pitts[6]  held that narco analysis results were unreliable. Their reliability will be proved by corroborating statements made during the analysis with other pieces of evidence procured.


This test was developed and patented in 1995 by neurologist Dr Lawrence. In this method, the accused is first interviewed and interrogated to find out whether he is concealing any information. Then sensors are attached to the subject’s head and the person is seated before a computer monitor. He is then shown certain images or made to hear certain sounds. The sensors monitor electrical activity in the brain and register P300 waves which are generated only if the subject has a connection with the stimulus which is the picture or the sound. Brain mapping received more support than other tools of interrogation.


Coming to the present case there were few questions deliberated by the courts:

  1. Are the tools being used violative of “due process in law”?

  2. Whether such techniques intrude the privacy of an individual?

  3. Are these techniques constitutionally permissible?

Answering the first question, one of the key features of due process is to understand where certain evidence has been obtained from. Due process ensures that no person is convicted because of coercing or illegally obtained evidence. It also ensures that regulations which are imposed by the police for conducting the investigation must not be arbitrary to the constitution. [7] In the present case, the main contention of the petitioners was that information being obtained is without the consent of the person and that is illegal. Hence, we can conclude that these tools violate the due process of law.

In relation to the second question, we must analyze Article 21 and Article 20(3) of the Constitution of India together to prove that such practices violate the privacy of an individual. As per Article 20(3) of the Constitution “No man can be made a witness against himself in court”. This principle is violated with the use of these tools because a man gives evidence against himself that too in a semi-conscious state. In fact, it is written in the Constitution that a man cannot be forced to answer all questions and his silence should be not be used against him in court. Coming to the aspect of Article 21 Right to Personal Liberty under its ambit also includes the right to a fair trial. In such cases, the evidence is taken out of forcing the individual and hence if it used cannot be termed as a fair trial. Such treatments also indicate inhuman and degrading treatment which goes against the principle of right to dignity. In fact, in the case of Rochin v State of California[8] it was held that drug-induced revelations can be held illegal as they intrude into the mental privacy of an individual.

In respect of the present case, referring to the Universal Declaration of Human Rights, International Covenant on Civil and Political Rights (ICCPR) and Convention Against Torture and other Cruel, Inhuman or Degrading Treatment or Punishment, 1984, it was held by the Supreme Court that any person who is forcibly subjected to the impugned tests in the environs of a forensic laboratory or a hospital would be effective in a custodial environment for the same. Thus, this point answers the third question and hence the courts in the present case held that such tests are inadmissible.


Even after this case the practice of administering such tools is prevalent but is restricted to only those cases where the person agrees to take the test as such tests can conclusively prove the guilt of the person. But such methods are only used to gather concrete evidence. This means that the test alone is not considered evidence but suppose an accused during a test reveals that he has hidden the murder weapon inside the building and the police find it such evidence will be accepted in court by the judge. In fact, in the Aarushi Talwar murder case both the parents and 3 Nepali men took the narco analysis test to prove their innocence voluntarily. The test leads to the many important facts being revealed and this helped the parents being acquitted by the court. Hence, we can say that these tests are helpful but they should be administered when the person voluntarily agrees to them. In one of the cases tried in the United States it was held that there is a difference in volunteering and being asked to volunteer. A person may say “I want to give the test.” This can be construed as voluntary acceptance. But a police officer saying “take the test to prove your innocence” is not voluntary and hence defeats the purpose of the right to privacy and self-incrimination. The courts in India must understand this difference when adjudicating on issues revolving these tools of interrogation.

[1] Selvi v State of Karnataka, (2010 ) 7 SCC 263

[2] United States v Scheffer, No. 96-1133, decided on 31st March, 1998: 44 M.J 442

[3] Phillion v R, 1978 1 SCR 18

[4] R v Beland, (1987) 2 SCR 398

[5] Townsend v Sain, 372 US 293 (1963)

[6] State v Pitts, 116 N.J. 580, 663-65, 562 A. 2d 1320 (1989)

[7] Berman v. Parker, (1954) 348 US 26

[8] Rochin v State of California, 342 US 165 (1952)