Opinion Op Ed 17 Feb 2016 The longest survivin ...
The writer is a senior advocate of the Supreme Court and former additional solicitor-general of India. He can be reached at knbhat1@gmail.com

The longest surviving lie

Published Feb 17, 2016, 1:03 am IST
Updated Feb 17, 2016, 1:03 am IST
The lie-detector test is like the ancient practice of ‘trial by ordeal’ used to identify a witch.
A file photo of Indrani Mukerjea and her daughter Sheena Bora (Left) (Photo: PTI)
 A file photo of Indrani Mukerjea and her daughter Sheena Bora (Left) (Photo: PTI)

In criminal cases when police resort to lie-detector tests 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. Take the recent instances of Peter Mukerjea in the Sheena Bora murder case and Salwinder Singh in connection with the Pathankot attack case — they both underwent the test and Mr Singh reportedly “cleared it”. Shashi Tharoor, in connection with the death of his wife Sunanda Pushkar in January last year is facing the threat of the lie-detector test.

In India the most popular form of lie-detector test is “narco analysis”, where the person is injected with a chemical — sodium pentothal — popularly known as the “truth serum”. The subject enters into a hypnotic trance and answers questions without having conscious control over the replies. Another test is the Brain Electrical Activation Profile (BEAP) test, also known as “P-300 wave test”, where electrical waves emitted from the test subject’s brain are recorded through electrodes attached to the scalp.


The subject is then exposed to external stimuli like sound and visuals relevant to the facts being investigated. The theory behind it appears to be that when exposed to material stimuli, the suspect emits P-300 waves on the basis of which the expert draws inferences.

According to Wikipedia, polygraph is a machine that can measure several physiological indices like blood pressure, pulse, respiration and skin conductivity simultaneously — hence named, polygraph — while the subject answers a series of questions.

The belief underlying the use of polygraph is that deceptive or untruthful answers will produce physiological responses that can be differentiated from those associated with non-deceptive or truthful answers. But, ultimately, the polygraph analysis is like any opinion, say that of a handwriting expert. Mr Singh clearing the lie-detector test means nothing because it is an established fact that the body of a habitual liar does not react differently while giving evasive answers or while uttering outright falsehood. At the same time, many innocent individuals passionate to establish their innocence fail the test due to the fear that the findings might possibly go wrong.


For these, and other reasons, the findings of a lie-detector test are not admissible in any legal proceedings in India, which is also the case in major parts of the world. Many from the scientific community assert that the lie-detector test is a big lie; that it is pseudo-science. If that is indeed the case, it is one of the longest surviving fakes, still in circulation world over since the invention of the polygraph in 1921 in California.

All lie-detector tests are invasive. Hence, a person cannot be subjected to a lie-detector without his/her consent, because Article 20(3) of the Constitution of India guarantees that no person accused in a criminal case shall be compelled to be a witness against himself or herself.


This question came up before the Supreme Court of India in Selvi vs State of Karnataka (2010). The court, by a detailed judgment, after examining authorities from the world over held: “The use of narco-analysis, brain-mapping and polygraph tests on accused, suspects and witnesses without their consent is unconstitutional and violation of the ‘right to privacy’.” In criminal cases, the protection of Article 20(3) extends to the investigative stage as well.

The National Human Rights Commission of India had, in 2000, published guidelines for the administration of polygraph tests. The Supreme Court, in Selvi’s case, directed that these guidelines be strictly adhered to. The guidelines are as follows:
No lie detector tests should be administered except on the basis of consent of the accused. An option should be given to the accused whether s/he wishes to avail such test.


If the accused volunteers for a lie detector test, s/he should be given access to a lawyer and the physical, emotional and legal implication of such a test should be explained to him/her by the police and his/her lawyer.

The consent should be recorded before a judicial magistrate.

During the hearing before the magistrate, the person alleged to have agreed should be duly represented by a lawyer.

At the hearing, the person in question should also be told in clear terms that the statement that is made shall not be a “confessional” statement to the magistrate but will have the status of a statement made to the police.


The magistrate shall consider all factors relating to the detention, including the length of detention and the nature of the interrogation.

The actual recording of the lie-detector test shall be done by an independent agency (such as a hospital) and conducted in the presence of a lawyer.

A full medical and factual narration of the manner of the information received must be taken on record.

Surprisingly, in spite of this knowledge, the media in India considers it sensational if someone is about to undergo a lie-detector test.
In the US, there is little scope for the use of third degree methods to extract a confession because of the “Miranda principle”. According to this, an accused about to be interrogated in custody has a right to demand the presence of a lawyer of his/her choice. In addition, there are stringent safeguards against custodial torture. The police there use lie-detector tests extensively as an intimidatory tool to extract confession.


Typically in the US, there are DVDs and literature on “how to fool lie detectors” and some of the authors are facing prosecution for this. In India too, lie-detector tests are part of the tactics used by the police — lay people prefer making confessions to undergoing tests that they fear. Occasionally, the test results may provide the right direction to the investigator.

The lie-detector test is a double-edged sword. If the accused refuses to undergo it, s/he is seen as someone who is trying to hide something. If s/he agrees then there’s the danger of the machine wrongly finding him/her a liar. And the media will condemn the accused. It is like the ancient practice of “trial by ordeal” used to identify a witch. The subject would be thrown into a raging river — if she floated, she undoubtedly was a witch and stoning could follow. If she sank, no scope for further questions.


Resort to lie detector in India is just an excuse for the police to steal a nap while real investigations stall. Should we retain this drama as an investigative tool?