Legal Validity of Lie-Detector Tests

Syllabus: GS2/ Governance

Context

The Central Bureau of Investigation (CBI) conducted a second round of polygraph tests on seven people, in connection with the rape and murder of a doctor at the R.G. Kar Medical College in Kolkata.

Deception detection tests (DDTs) are scientific procedures employed to detect probable deception during interrogation.
These tests include narco-analysis, polygraph tests, and brain mapping.

A polygraph test operates on the presumption that specific physiological responses are triggered when a person is lying.
The test is administered by attaching instruments like cardio-cuffs or sensitive electrodes to the suspect to measure variables such as blood pressure, galvanic skin response (a proxy for sweat), breathing and pulse rate.
As questions are posed, each physiological response is assigned a numerical value to determine whether the individual is telling the truth or being deceptive.

It involves the injection of a drug called sodium pentothal into the accused, inducing a hypnotic or sedated state.
The assumption is that a subject in such a state is less inhibited and is more likely to divulge information.
- Because the drug is thought to weaken the subject’s resolve to lie, it is often referred to as a “truth serum.”

It measures a subject’s neural activity, specifically brainwaves, using electrodes attached to the face and neck.
It operates on the principle that the brain generates distinctive brain waves when exposed to familiar stimuli, such as an image or a sound.

Prior to 2010, Indian courts were strongly in favor of these tests. They pitched these “scientific methods of investigation” as a safer alternative to the custodial violence often used to extract information.
The Supreme Court in 2010 in the case of Selvi v. State of Karnataka ruled that no lie detector tests should be administered “except on the basis of consent of the accused” in accordance with the fundamental right against self-incrimination as enshrined under Article 20(3) of the Constitution.
Further it was elucidated that a person’s right to make a statement or remain silent is integral to their right to privacy.
- Thus compelling an individual to make a statement would also constitute a violation of Article 21 of the Constitution.
The Court also noted that little empirical evidence is present to bolster the argument that these tests provide reliable leads for investigators.
It cautioned that the results of these tests cannot be regarded as confessions.
- However, if any information or material is subsequently discovered “with the help of voluntarily administered test results,” such evidence can be admitted in court.
Additionally, it required that the subject’s consent be formally recorded before a judicial magistrate and that the guidelines set out by the National Human Rights Commission in 2000 for administering these tests be strictly adhered to.

In a 2010 paper published in the Indian Journal of Medical Research, it was observed that lie-detection techniques have faced a number of criticisms, and their effectiveness in revealing “concealed knowledge in applied real-world settings” remains uncertain.
It argued the reliability of polygraph tests, pointing out that the test’s underlying principle is flawed—parameters such as heart rate and blood pressure have not been proven to be uniquely indicative of lying.
Similarly, a 2019 study conducted in the United States flagged high false positive rates and noted that individuals can train themselves to beat a polygraph.
Despite the Supreme Court’s cautionary stance, the administration of these tests continues to be prevalent in India.

Source: TH

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