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‘Hathras case- Issues of consent, reliability in narco and polygraph tests’

Published: 12th Oct, 2020


  • A spokesperson for the Uttar Pradesh government recently said that polygraph and narcoanalysis tests would be conductedas part of the investigation into the alleged gangrape and murder of a 19-year old Dalit woman by four men of the Thakur caste in Hathras last month.

 Polygraph and narcoanalysis tests

  • A polygraph testis 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 information that is true.
  • 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.

Supreme Court’s ruling on 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.

Can people other than the accused in a criminal investigation — witnesses, victims, their families — through these tests?

  • The Supreme Court had said in its order that “no individual should be forcibly subjected to any of the techniques in question, whether in the context of investigation in criminal cases or otherwise”, and expanded the same rule to others who can be made to undergo the test only if they consent to it.
  • It had said that forcing an individual to undergo these tests amounts to an “unwarranted intrusion into personal liberty”, but had left scope for “voluntary administration” of these techniques if the individuals gave consent.
  • The court examined the scope of Article 20(3), the right against self-incrimination, which states that no accused can be compelled to be a witness against himself.
  • It said that while this requires a person to be formally named as an accused, other provisions of the Criminal Procedure Code extend this protection to witnesses as well.
  • With reference to victims, especially of sexual offences, the Bench said that irrespective of the need to expedite the probe in such cases, a victim of an offence cannot be forced to undergo these tests as it would be “an unjustified intrusion into mental privacy and could lead to further stigma for the victim”.

Criminal cases in recent years where these tests been used

  • In most cases, investigating agencies seek permission for such tests to be done on accused or suspects, but rarely on victims or witnesses.
  • Legal experts say that investigating agencies can submit to a court that the tests are being sought to help in their probe but consent or refusal to undergo the tests by an individual do not reflect innocence or guilt.
  • Most recently, the CBI has sought to conduct these tests on the driver and helper of the truck that hit the Unnao rape victim in Uttar Pradesh in July last year. It also sought to conduct the tests on one accused in the Punjab National Bank alleged fraud case, but the court rejected the plea after the accused did not give consent.
  • In May 2017, the founder of INX Media, Indrani Mukerjea, who is facing trial for the alleged murder of her daughter Sheena Bora in 2012, had offered to undergo the lie detector test, which was refused by the CBI, stating that they had sufficient evidence against her.
  • The polygraph test was also conducted on Dr Rajesh Talwar and Dr Nupur Talwar, who were accused of killing their daughter Aayushi and help Hemraj in Noida.

Critical analysis of polygraph:

  • The test does not tell as to whether the subject is lying or not. Results only show about the physiological changes which have to be interpreted by the expert.
  • In asking the question no science is involved and it wholly depends upon trickery and on the expertise of the examiner.
  • A person who can control his emotions to a great extent can still tell a lie, e.g., if a person has control on himself by practice of yoga or otherwise, this test is bound to fail.
  • Nervousness may be exhibited by many innocent and truthful persons under the conditions of police interrogations. This nervousness may arise due to various reasons, e.g., fear of being involved in the crime, or the fear that his or her previous conduct may be shown to the police what is not related to the present crime.
  • It may also be due to the fact of not properly understanding the procedure of polygraph, besides there may be fear of wrong interpretation of chart by the examiner and even the interrogator and examiner may be biased.
  • If the examiner holds the subject guilty, he may interpret the chart with that bent of mind and vice versa he may be lenient in interpreting, chart of a person whom he considers innocent.

Critical analysis of brain mapping

  • This test has its own limitations. The test is conducted by a human being and it is possible that they fail to fully and truthfully analyze the brain wave.
  • An innocent person who has not committed the crime but has only witnesses of wound also react to the stimuli. Similarly, a person may be aware of the crime due to details published in media and the brain may store it. In that case also there chance is that the innocent can also be found guilty.
  • Therefore, this tests utility is only to imprint the subject’s brain, which makes it clear that the subject is innocent.
  • This technique is also criticized on the ground that it is violation of brain privacy. By this a person loses his right to keep his thought to himself.
  • This is also not useful in case of a person who loses his memory, e.g., old people easily lose memory.


 As India is confronted with cross-border terrorism and a tough internal security scenario hence use of technologies are vital for the nation to deal with these challenges. However, rapidly and swiftly these scientific tools of investigation can become an alternate of third degree physical torture in police custody. As was rightly held by the Supreme Court in D. K. Basu v. State of West Bengal , that there is need for developing scientific methods of investigation and interrogation of accused as custodial deaths and torture is nothing but a blow at rule of law.

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