Called the ‘Lie Detector Tests’, several instruments are used including cardiographs, sensitive electrodes and injections in the course of these examinations to put a person in a hypnotic state to ‘reduce’ their ability to lie or manipulate.

CBI wants to conduct polygraph and narcoanalysis tests on a former staffer of Punjab National Bank (PNB), who is in custody in the alleged Rs 7,000-crore fraud involving the absconding jewellers Nirav Modi and Mehul Choksi.

On Wednesday, Gokulnath Shetty, the 63-year old retired deputy manager of PNB, refused to give his consent for the test, stating among other reasons, that it could have an adverse effect on his health. He also cited a Supreme Court judgment that makes it mandatory to obtain the consent of the accused for such tests.

What are polygraph, narcoanalysis tests?
A polygraph test is based on the assumption that physiological responses that are triggered when a person is lying are different from what they would be otherwise. Instruments like cardio-cuffs or sensitive electrodes are attached to the person, and variables such as blood pressure, pulse, respiration, change in sweat gland activity, blood flow, etc., are measured as questions are put to them. A numerical value is assigned to each response to conclude whether the person is telling the truth, is deceiving, or is uncertain.

A test such as this is said to have been first done in the 19th century by the Italian criminologist Cesare Lombroso, who used a machine to measure changes in the blood pressure of criminal suspects during interrogation. Similar devices were subsequently created by the American psychologist William Marstron in 1914, and by the California police officer John Larson in 1921.

Narcoanalysis, by contrast, involves the injection of a drug, sodium pentothal, which induces a hypnotic or sedated state in which the subject’s imagination is neutralised, and they are expected to divulge true information. The drug, referred to as “truth serum” in this context, was used in larger doses as anaesthesia during surgery, and is said to have been used during World War II for intelligence operations.

More recently, investigating agencies have sought to employ these tests in investigation, and are sometimes seen as being a “softer alternative” to torture or ‘third degree’ to extract the truth from suspects.

However, neither method has been proven scientifically to have a 100% success rate, and remain contentious in the medical field as well.

Are Indian investigators allowed to put suspects through these tests?
In Selvi & Ors vs State of Karnataka & Anr (2010), a Supreme Court Bench comprising Chief Justice of India K G Balakrishnan and Justices R V Raveendran and J M Panchal ruled that no lie detector tests should be administered “except on the basis of consent of the accused”. Those who volunteer must have access to a lawyer, and have the physical, emotional, and legal implications of the test explained to them by police and the lawyer, the Bench said. It said that the ‘Guidelines for the Administration of Polygraph Test on an Accused’ published by the National Human Rights Commission in 2000, must be strictly followed.

The subject’s consent should be recorded before a judicial magistrate, the court said. The results of the tests cannot be considered to be “confessions”, because those in a drugged-induced state cannot exercise a choice in answering questions that are put to them.

However, any information or material subsequently discovered with the help of such a voluntarily-taken test can be admitted as evidence, the court said. Thus, if an accused reveals the location of a murder weapon in the course of the test, and police later find the weapon at that location, the statement of the accused will not be evidence, but the weapon will be.

The Bench took into consideration international norms on human rights, the right to a fair trial, and the right against self-incrimination under Article 20(3) of the Constitution.

“We must recognise that a forcible intrusion into a person’s mental processes is also an affront to human dignity and liberty, often with grave and long-lasting consequences,” the court said, observing that the state’s plea that the use of such scientific techniques would reduce ‘third degree’ methods “is a circular line of reasoning since one form of improper behaviour is sought to be replaced by another”.

In which recent criminal investigations have these tests been used?

The CBI has sought to give these tests to the driver and helper of the truck that hit the vehicle carrying the Unnao rape victim in Uttar Pradesh in July.

In May 2017, Indrani Mukerjea, who is facing trial for allegedly murdering her daughter Sheena Bora in 2012, had offered to undergo the lie detector test. The CBI refused, saying they already had sufficient evidence against her.

Dr Rajesh Talwar and Dr Nupur Talwar, who were accused of killing their daughter Aarushi and help Hemraj in Noida in 2008, were given polygraph tests. A video of the narco test on their compounder, Krishna, was leaked to the media.

Why has the CBI sought to use these tests in the PNB case?
The CBI has said that it has been unable to ascertain Shetty’s “other motives and details of undue pecuniary advantage obtained by him”. Shetty is alleged to have issued fraudulent Letters of Understanding in favour of Nirav Modi, Mehul Choksi, and their firms in violation of bank rules. Shetty has been in custody since March 2018. CBI has already filed the chargesheet in the case. The court will decide on Shetty’s refusal of consent next week.