Categories: JOURNAL


VOLUME:- 2  ISSUE NO:- 2 , AUGUST 1, 2023


SCIENCE v LAW: Analyzing the compatibility of Deception Detection Tests with Indian court proceedings


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Unveiling Truth: The Intersection of Science and Law

The pursuit of justice depends on the ability to unveil the truth, especially in legal proceedings where the conformity of statements and testimony is of the utmost importance.  The intersection between science and law has emerged as a potential tool to detect deception. The techniques like narco-analysis, brain mapping and polygraph test aims to uncover the hidden information and distinguish the truth from deception. However, it carries with it an intricate web of legal considerations, scientific reliability, and ethical implications.

The admissibility of these techniques in the courtrooms remains a contentious topic of debate, as it directly impacts the administration of justice and fairness of legal proceedings. Consequently, it becomes imperative to evaluate the compatibility of these Deception Detection Tests (DDTs) with the principles and standards of Indian law.

Unraveling the web of lies: Understanding DDTs

Brain mapping, commonly called Brain Electrical Activation Profile (BEAP) test or P300 Waves test, measures the fluctuations in the electrical field potentials of the brain that are caused by the activity of the neural networks. The underlying hypothesis is that whenever a person is exposed to a stimulus that they have experienced before, their brain generates a unique pattern. It is not expected that the person undergoing this test will provide any kind of verbal answer. This test is quite popular in India and was administered in the cases like Arushi Talwar murder case, Hathras case and Nithari serial killings.

Narco-analysis is also sometimes referred to as the truth serum test. It entails the controlled intravenous administration of hypnotic truth drugs, such as sodium pentothal, scopolamine, and sodium amytal, to a suspect so as to induce a state of semi-consciousness. In this hypnotic state, the subject is more likely to disclose information that he might not reveal in his normal state of consciousness. This test was used in India in the cases like, Abdul Karim Telgi fake stamp paper scam, 2002 Gujarat riots case and Shraddha Walkar murder case.

Polygraph test also called lie detector test, which uses a baseline which is established by asking certain questions whose answers are already known, and any deviation from this baseline is considered as a sign of lie. Theoretically, when a person lies, they experience certain physiological changes and produces a hyper-arousal state which can be measured. The polygraph machine records the parameters like blood pressure, pulse rate, respiration, muscle movements and skin conductance. It was used on Aftab Poonawala in the Shraddha Walkar murder case.

With the help of these scientific methods, it is now possible to determine if a person is deceiving. However, wherever science and law collide, some ethical and legal concerns arise.

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Balancing Justice and Constitutional Rights

Article 20(3) of the Indian Constitution is a fundamental canon of common-law criminal jurisprudence, which states that “No person accused of any offence shall be compelled to be a witness against himself”. Over the years, this Article has been interpreted various times by the Supreme Court. The Apex Court in of M.P. Sharma v Satish Chandra had stated that “the phrase ‘to be a witness’ in this Article meant ‘to furnish evidence’ and this could be done through lips, or by production of a thing or a document, or in any other mode”. This made the stance clear regarding the Narco-analysis test which requires the subject to make oral statements ‘through his lips’. Subsequently, in State of Bombay v Kathi Kalu Oghad, SC opined that “self-incrimination must mean conveying information based upon the personal knowledge of the person giving the information and covers only personal testimony which must depend upon his volition”. In its 2010 judgment of Selvi v State of Karnataka, the question pertaining to the constitutional validity of involuntary or compulsory administration of scientific techniques, i.e. Narco-analysis, polygraph test and BEAP test were made crystal clear. The Court concluded that the results obtained through any of these impugned tests were within the ambit of ‘testimonial compulsion’ and can very well attract Article 20(3) as a hedge against harm, and when read with §161(2) of the CrPC, it has the ability to protect ‘accused persons’, ‘suspects’ and ‘witnesses’ who are examined during an investigation.

Subjecting a person against their will to any of these scientific techniques would constitute an ‘unwarranted intrusion into the personal and mental liberty’ of that individual, and ‘cruel, inhuman or degrading treatment’. Furthermore, relying on these test results runs counter to the ‘right to fair trial’. The executive power cannot hinder the constitutional rights, or any other rights of a person, and in the absence of a law, an infringement on fundamental rights must be deemed unconstitutional.

The Legality & Admissibility of Scientific Techniques

When seen through the lens of Sections 53, 53-A and 54 of the CrPC, these scientific techniques do not collapse to the confines of the provision for medical examination during investigation in criminal cases.

According to the current scenario, the results from any of these tests can’t be admitted as evidence if they are obtained through coercion or compulsion. However, Section 45 and 45A of Indian Evidence Act allows the court to take opinion from an expert in any field concerning the case. Person’s choice between speaking and remaining silent is safeguarded by allowing for the voluntary administration of these techniques. Even if the person concerned has granted his/her consent to undergo any of these scientific tests, the result itself cannot be admissible as evidence since the subject is in the state of semi-consciousness and does not have conscious control over the replies while the test is being administered. Nonetheless, according to Sec.27 of the IEA, any material or information that is discovered subsequently with the aid of voluntarily administered test results may be admitted.

Accuracy and Limitations of DDTs

These tests are not always 100% accurate. There’s always a room for the subject to make false statements. When administering the Narco-analysis it is extremely difficult to prescribe or recommend a specific quantity of the truth serum, as the dosage is highly dependent on the mental and physical conditions of the person concerned. The reading of the polygraph test may not always indicate that the subject lied; the person concerned may have been in a state of dread or panic due to his surroundings or because he was being interrogated. Brain mapping relies solely on the person’s acquaintance with the information related to the crime. It is possible that the subject is acquainted with the information due to his exposure to such images, videos, or audios via social media, the newspaper, or any other source. It is not sufficient to conclude that the subject is associated with the crime.

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The Need for Legislative Clarity and Enforceable Rules

As per the Guidelines for the Administration of Polygraph Test on an Accused, which were published by NHRC in 2000, the “statement made by the person in question shall not be a confessional statement to the Magistrate but will have the status of a statement made to the police”. These guidelines were made after a petition by Shri Indra P Choudhary in 1997. These guidelines should be acclimatized to and equivalent safeguards should be exercised and adopted while administering the Narco-analysis and the BEAP test.

In Rojo George v Deputy Superintendent of Police, the court allowed the narco-analysis test stating that “in the modern era, criminals have adopted highly sophisticated and innovative methods for committing crime.” Therefore, the conventional methods of investigation and interrogation of criminals will not be an effective solution, and new techniques, such as DDTs are required.


DDTs are controversial tools that have been used in criminal investigations for many years. While there is no consensus regarding their reliability, they can have a significant impact on lives of individuals. Therefore, it is essential to have explicit and enforceable rules governing the use of these tests.

Legislation would provide clarity and certainty about the use of deception detection tests in India. It would also help in safeguarding the rights of those who are subjected to these tests. The law should take pragmatic view of the matter at hand by taking into account the current capabilities of technology and life style of community.

Allowing the administration of DDTs on the accused of heinous and grave offences could prove to be an aid in improving the quality of the criminal justice system. However, it is important to ensure that these tests are administered in a fair and ethical manner.

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