Why Are Lie-Detector Tests Still Being Used In Criminal Investigations?

By Kedar Nagarajan | 11 July 2017

In a piece published in the Deccan Chronicle in February 2016, KN Bhat, the former additional solicitor general of India, writes: “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.”

The debate over the use of the lie-detector test has been ongoing in India for a long time. Like Bhat, several legal and scientific experts have long argued against its accuracy and high rates of error. Further, rights-based activists and organisations have previously opposed the test on humanitarian grounds, stating that it violates the fundamental rights of the person being subjected to it.

In India, the issue came before the Supreme Court in the case of Selvi vs State of Karnataka. In 2010, the court delivered a detailed judgment, in which it tested lie-detection techniques on two primary grounds. The first was whether the use of the tests could violate Article 20 (3) of the constitution, which states that no person accused of an offence shall be compelled to be a witness against herself. The second was whether the administering of such tests without the explicit consent of the person accused constituted a direct violation of Article 21—the right to life and personal liberty. The court ultimately forbade investigative agencies from making the test compulsory. “The use of narco-analysis, brain-mapping and polygraph tests”—the three commonly used types of lie-detection tests—“on accused, suspects and witnesses without their consent is unconstitutional and a violation of the ‘right to privacy,’” the court noted. It also noted that little empirical evidence is present to bolster the argument that the tests provide reliable leads for investigators.

Yet, investigating agencies and prosecutors in criminal cases continue to request lie-detector tests. Several prominent investigations in recent years have included such a focus: the senior Congress leader Jagdish Tytler, who has been named in several cases related to the 1984 anti-Sikh riots, is currently appearing as a witness in a case pertaining to the deaths of three Sikh men in the Pulbangash gurdwara in north Delhi during the riots. The Central Bureau of Investigation requested that Tytler undergo a lie-detector test “for the purpose of further investigation.” Tytler refused to do so, and the CBI’s plea to conduct a test on him is being heard in a Delhi court. In the case of Najeeb Ahmed—a student at the Jawaharlal Nehru University in Delhi who went missing in October 2016—the Delhi Police asked nine suspects to take a lie-detector test. The crime branch of the police stated in a notice to the students on 23 January 2017 that the test was required in order to obtain information about Najeeb’s whereabouts. Other cases that have employed lie-detection techniques include the case of the murder of Aarushi Talwar, and the cases against Peter and Indrani Mukerjea.

The reason for this undue focus is unclear. According to Keshav Kumar, a former CBI officer and current additional director general of the Gujarat Police, the test is essential because “the traditional system of investigation has failed.” “Sometimes cases take so long that the person in question of the crime—or even a witness—either forgets certain details of a case or is influenced during the proceedings to have a selective memory,” Kumar said. A lie-detector test “is only an aid,” he continued, and added that it serves to reassure an investigative officer about the course of her investigation.

Kumar’s assertion appears to rest heavily on the assumption that the results of the lie-detector tests are reliable. However, there is little scientific evidence to support this.

Lie-detector tests employed in criminal investigations are usually one of three different tests. The first is a polygraph test—it is often incorrectly assumed that lie-detection refers only to this method—during which the physiological responses of a person, such as her heart rate, blood pressure, and respiratory rate, are measured. The assumption underlying this test is that a guilty person would intend to lie about the facts of the case, and that this would induce a state of hyper-arousal—irregular or heightened physiological responses. The second is the narco-analysis test, in which a medical professional intravenously administers a drug, such as sodium pentothal or sodium amytal—often termed “truth serums”— that causes the subject to enter into a semi-conscious state. Here, the assumption is that a subject in such a state is less inhibited and is more likely to divulge information. The third is the brain-mapping test, which measures a subject’s neural activity—her brainwaves—via electrodes placed on the surface of her face and neck. This test is based on the idea that a person’s brain would produce a unique brainwave when it encounters a familiar stimulus, such as an image or a sound.

According to GV Rao, a DNA-testing expert based in Hyderabad, since the lie-detector tests may involve questioning a person who is in a semi-conscious state, it could be equated to interrogating “a drunk person.” Rao regularly assists legal teams with DNA-based testing for their cases. “Unlike DNA and other forensic practices used in criminal cases, the lie-detector lacks any global consensus on its validity,” Rao added. He said that across the world, several legal systems such as that of the United Kingdom, do not accept results of a lie-detector test as evidence.

In a 2010 paper published in the Indian Journal for Medical Research, Suresh Bada Math, a psychiatric expert, writes that lie-detection techniques have “faced a number of criticisms and it is still unclear to what degree lie detectors and brain mapping can be used to reveal concealed knowledge in applied real-world settings.” “The reliability of the polygraph test has been repeatedly questioned in empirical studies,” Math notes. He added that the principle for the test itself was questionable—the parameters such as heart-rate and blood pressure, that indicate a state of hyper-arousal, have not been proven to be uniquely indicative of lying. Math states that studies regarding the reliability of the narco-analysis test have been “inconclusive.” The “applicability of this technique in the forensic field is remote at this point of time,” he writes.

According to Rebecca Mammen John, a senior advocate, tests such as the lie-detector test “masquerade” as scientific tests. “It is some mumbo-jumbo that no one understands,” she said.

Even if a lie-detector test assisted an investigation by “throwing up a new lead,” John added, statements made during such a test are not admissible as evidence in court. This is part of the Selvi judgment: the court noted that the results of these tests are inadmissible “because the subject does not exercise conscious control over the responses during the administration of the test.” Simply put, “you can’t say that we got this lead from a lie-detector test, a narco-analysis test or a brain mapping test,” John told me.

The court noted, however, that “any information or material that is subsequently discovered with the help of voluntary administered test results can be admitted.” John said that in her 30 years of experience as a lawyer, she is yet to come across a case where the results of a lie-detector test have solved a crime.

When I asked Kumar about this, he said that if the evidence is not admissible in court, “that is for the court to be cognisant of.” “The Supreme Court judgement states that the test cannot be conducted without the consent of the person, if there is consent then what is the problem?” Kumar said. He added, “The accuracy of DNA analysis has been contested globally as well.”

Both John and K Saleem Ali, a former special director of the Central Bureau of Investigation, said that investigative agencies frequently demand the test because the quality of the work during the initial stages of inquiry in India is “poor.” “All these tests are substitutes for lazy investigation,” John said. “When you are unable to investigate a case in a robust manner, tests like these are called for.”

Ali added that sub-inspectors in India are “not being given proper training.” “I have interacted with police personnel at the sub-inspector level in Bangladesh and Sri Lanka and all of them are frequently sent overseas to receive proper training for the purpose of investigation,” Ali told me. “That is unfortunately not the case here.” If these officers were properly trained, Ali added, “pseudo scientific” methods of criminal investigation would be done away with. The test is “a complete invasion of a person’s privacy,” he added.

John pointed to other issues with the test. What bothered her most about the test, she said, was that ordinary citizens are often not aware that a test such as this cannot be conducted without their consent. She added that the prosecution often uses a person’s unwillingness to undergo a lie-detector test to cast a judgement on their character before the court. “My experience in court has shown me that prosecutors come to court while bail and anticipatory bail applications are being heard and say that this person is not entitled to any benefit of the law because he or she has refused to undergo the lie-detector test,” she said. “The fact that you have used your constitutional right is used against you to suggest mala fide conduct.”

Bhat had echoed this point in his article. Terming the test a “double-edged sword,” he wrote: “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.”

“Nowhere in the world are tests like the narco-analysis test used, and yet in India it ruled the field for a pretty long time before Selvi came into operation,” John said. She cited the Kobad Ghandy case—in 2009, Ghandy had been arrested and charged under the Unlawful Activities (Prevention) Act and under offences in the Indian Penal Code, allegedly for being a member of the banned organisation the Communist Party of India (Maoist). John had represented Ghandy. She told me that, while hearing the case, a trial court ordered a lie-detector test. “When I challenged it, I was ruled against. It was only when I challenged the ruling at the high court that the test was declared unconstitutional,” John said.

According to Rao, one reason for the continued use of the test is that directives in the Selvi judgment have not been properly implemented. “The Supreme Court made the observations in that judgement and left it at that, but there was no direction from the government to all the state home secretaries or ministries that henceforth do not adopt this technology,” he said, adding that only lawyers aware of the judgement were able to contest the test. “Police works only on directions, so unless the home secretary, DGP or SSP [the director general or senior superintendent of police, respectively] or somebody sends them a letter, they will be following the same practice.”

John said that she was “shocked” that courts continued to allow the use of the test. “I am on the side of Najeeb in that my sympathies are with him and his family,” she said. Yet, she continued, she was opposed to the suggestion that the nine students accused of being involved in his disappearance undergo a lie-detector test. “That is completely unconstitutional,” she said.

Kedar Nagarajan is a web reporter at The Caravan.


2 thoughts on “Why Are Lie-Detector Tests Still Being Used In Criminal Investigations?”

The “methods of investigation” adopted by the police (in most situations) involves rounding up listed rowdy-sheeters, informers and interrogating them until some version (fact is not the important thing here — an admission is) of what happened emerges. Lie detector tests fall into the same category.

Hi there, I read through a few of your articles here. I
did have a question though that I hope you could answer.

I was wondering, How do police officers understand/learn about laws in order to make arrests?
What training do police receive on laws/ legal issues? And how do they stay up-to-date
on new laws? I would really appreciate any help you could give me!

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