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Author: M. Rajendra Rushi, V year of B.A.,LL.B. from Ramaiah College of Law

Very often in Indian movies, it is depicted especially during the interrogation or police investigation of heinous crimes or crimes against the state, the suspect can be seen put toa lie detection test. But what exactly is this procedure?Why do we need this lie detection test? Is it legal in India?

The term crime has its origin inthe Latin “crimen” which means ‘charge’, ‘fault’ or ‘cry of distress’. The main aim of the criminal justice system is to identify the crime and criminal, to judge them and punish the offender or wrongdoer and bring justice to the victim.The criminal justice system aims to make sure to punish the offenders for the crimes committed and brings reformation in them. It should see that those offenders do not commit any crimes in the future and should provide justice to the victim against whom the injustice has taken place. The criminal justice system can be considered an interdisciplinary subject comprising the judiciary (making of laws), and executive (enforcing laws)& policing. Narrow down the problem arising out of the crime and the changes in technology, innovation, and introduction of advanced technology in the criminal justice system have an impact on the outcome of the rulings and landmark judgments. There are various techniques like Narcoanalysis, Polygraphy, Brain Mapping,etc., collectively known as Deception Detection Tests (DDT).

The former solicitor general of India KN Bhat opines that ”in criminal cases when police resort to lie detector test it should be concluded that the investigation has reached a dead end and other methods of discovering evidence or eliciting information, including procuring a confession, have failed.”

There have been many questions raised and had been debated on the usage of lie detectors in the field of criminal investigation, many jurists and human rights activists argue that it is a gross violation of a person’s fundamental rights and human rights.

Lie detectors are instruments that study the physical changes in the body of the person who is being questioned by the respective officials or the examinerand determine whether he’s giving a true answer or not by measuring their pulse rate, heartbeat and breathing rate, etc. The examiner studies the body language of the suspect when he answers and concludes whether the person is lying or not, it is considered to determine the authenticity of the person’s statement.

Every individual who is directed to undergo a lie detection test has a choice either to give consent or not. In case when the suspect, witness,or any relevant person to the investigation does not give voluntary consent for the test, then the investigating authorities have no right to conduct the test.If the test is done by Inducement, coercion, or fraud then it is void ab initio. This test comes under the proviso of ‘torture’ under Article 1 of the United Nations Convention against Torture if there is a lack of consent.

The maxim “Nemo tenetur seipsum provider” signifies that no one is bound to accusehimself, as the Indian Judiciary believes in the principle of ‘presumption of innocence’. Article 20(3)[i] of the Indian Constitution and Section 161(2) of the Code of criminal procedure, 1973also provide rights to the suspect from self-incrimination. Article 20(3) withstands the principle i.e.,‘innocent until proven guilty’ and no suspect can be forced to be a witness against himself in his case, as it is a violation of fundamental rights. In the majority of cases, the burden of proof shall lie on the prosecution. In the case of M.P. Sharma v Satish Chandra[i], the Hon’ble Court affirmed that the right under Article 20(3) not only confines courtroom proceedings but also protects the right against self-incrimination of the witness, suspects, and the accused.

Many legal, medical, and psychological experts criticized the reliability of this test as it showed a significant effect on the subject’s body, there are cases where the suspect diedfrom over dosage of drugs during the narcoanalysis. As we know, these tests are not physical, unlike DNA or fingerprint tests.

Some instances resulted in physical threatsorintimidationof suspects or witnesses because of which they were forcibly given consent to these tests, which are not legally admissible or do not prove the intent behind the test. It also gives rise to various doubts about the credibility and validity of the test. The test also raises the question of the right to privacy and dignity and its balance with self-incrimination which is a pivotal right enshrined in the Constitution of India under Article 21.

Selvi V. State of Karnataka[ii]

A 256-page judgment delivered by a 3 Judge bench consisting of the then Chief Justice of India K.G. Balakrishnan along with Justice R.V Raveendran and Justice J.M Panchal had witnessed many writ petitions regarding the legality of lie detectors. Amongst them, the court considered one Special Leave Petition. Here the suspects, witnesses, and accused were subjected to a Narcoanalysis test, Brain Electrical Activation Profile (BEAP), Functional Magnetic Resonance Imaging (FMRI), and Polygraph test without their consent of them during the investigation. The issues that came before the Supreme Court were that:

  • Firstly, the constitutional validity and legality of the tests were questioned.

  • Secondly, the issue raised was whether the tests violated the right against self-incrimination provided under the provisions of Article 20(3) of the Indian constitution and Section 161(2) of CrPC.

  • Thirdly whether the tests conducted without the consent of the subjects violate the provision of Article 21 or not?

In this case, the court forbade the investigating agencies from practicing the above-mentioned tests withoutthe consent of the individuals as it violates the Right to Life and Personal Liberty guaranteed under Article 21 of the Indian Constitution. It also did not mandate the tests. The courts reiterated the fact that the tests can be conducted with prior consent and voluntarily by following the safeguards. The court further clarified that even after the consent of the accused, witness, or suspect and when they undergo these tests, if they are unable to exercise conscious control of their response then those tests cannot be relied on or considered as valid shreds of evidence.

The use of Narcoanalysis, Brain Mapping, and Polygraph tests are three common types of Lie Detection Tests and if the consent of the accused, suspect, or witness is not obtained then it is said to be unconstitutional and is violative of the ‘Right to Privacy’.It has been argued that the results gathered from scientific techniques such as narcoanalysis, polygraph examination, and Brain Electrical Activation Profile (BEAP) test comes into conflict with the ‘Right to a Fair Trial’. However, any information obtained or subsequently discovered during the voluntary test process can be admitted and can be considered as evidence under Section 27 of the Indian Evidence Act.

Safeguard measures are to be followed while conducting the Narcoanalysis and Brain Electrical Activation Profile Test (BEAPT),as per the guidelines directed bythe National Human Rights Commission (NHRC) which published ‘Guidelines for the Administration of Polygraph Test or Lie Detector Test on an Accused in the year 2000.

  • Consent and the Option of availing of the test should be given to the accused, witness, or suspect.

  • A Police or an advocate has to explain all the mental, emotional, and legal implications of the test. The subject should be duly represented by an advocate in the matter.

  • The consent should be recorded before the judicial magistrate along with the medical and factual narration.

Evidentiary value of such tests

The Indian judiciary had given both prospects of acceptance and non-admissibility of such tests through various judgments. But at the same time, it is valid only when there is voluntary consent of the subject and when there isa sign of coercion, threat, intimidation, or any kind of external influence then such tests would be meaningless under Section 24 of the Indian Evidence Act, as they are not conscious when they are under narcotic drug tests. This test cannot be regarded as an expert opinion.Section 45 of the Evidence Act, of 1872 deals with expert opinion, “when the court has to form an opinion upon a point of foreign law or of science or art, or as to identify of handwriting [or finger impressions], the opinions upon that point of persons specifically skilled in such foreign law, science or art are relevant facts”.


However,whether to follow the concept of a lie detector test or not is still ambiguous, the Constitutional validity and the authenticity of the lie detector are still in question. At the same time, we have various Supreme Court and High Courtjudgments where the courtsleft the test to the discretion of investigating authorities. When there arises a situation where there is a violation of any fundamental right during the test, then the process is said to be void. As we can notice that in many instances these lie detectors have been manipulated, by controlling their feelings and emotions because in the end the lie detector determines and detects the physiological change in the body and accordingly gives out the results.

Lie detector tests are also considered violative of the right to life and personal liberty, a Fundamental Right under Article 21, enshrined in Indian Constitution. This concept is regarded as cruel, inhuman, or degrading treatment in the context of Article 21.This is an opposing concept of the right against self-incrimination which is provided under Article 20(3) and Section 161(2) of CrPC. As the principle is based on human skin resistance, the person who is subjected to the test, if that person is lying confidently then it is a Hercules task for the lie detector to catch a lie because in that case the person therewon’t be any change in his body like sweating or feeling nervous, etc.Thus, there are various cons in considering or validating the usage of lie detectors in the field of a criminal investigation.

[i] (1954) SCR 1077 [ii] AIR 2010 SC 1974


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