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Deception Detection Techniques In Contemporary Criminal Justice System

Early enough, English jurist William Blackstone had said that it is better that ten guilty person escape than one innocent suffer. This statement holds significance even in modern justice system as wrongful conviction does not just involve individual who has been wrongly punished instead it has dreadful ramifications upon his or her entire family, therefore, the fair and accurate investigation of offence which can lead to nothing but truth is indispensible.

However, eliciting truth from criminals or witnesses or victims has always been a daunting task, in ancient societies, many torturous activities like ordeal by water, fire, poison, rice, red hot iron boiling oil etc. were used to identify liars with a view that divine intervention would protect the truth speaker. In our modern criminal justice system too, investigating authorities frequently employ various scientific lie detector techniques or deception detection tests (DDT) such as Polygraph, Narco-Anaysis, and Brain Mapping etc. to find out the truth. These devices involve various scientific processes such as observing behavior, analyzing speech, measuring peripheral physiological responses or recording brain activity.

In this article, at first, we will try to understand these three forms of lie detectors in a detailed way and also check their constitutional and legal implications along with discussing out their effectiveness.

Forms of Lie Detectors:
Generally we tend to associate Polygraph with lie detection, however, Polygraph, Nacroanalysis and Brain mapping are the three methods of lie detection used by investigating authorities, each of these involves different strategy & mechanism. Let us understand all of them one by one.
  • Narco Analysis: This test involves the intravenous administration of a drug that causes the subject to enter into various stages of anesthesia. In the hypnotic stage, the subject becomes less conscious and is more likely to divulge information, which would usually not be revealed in the conscious state. However, this technique is not free of flaw as some persons are able to retain their ability to deceive even in the hypnotic state, while others can become extremely suggestive to questioning. Besides, The drugs used, do not guarantee that the subject will speak only the truth as statements made in a hypnotic state are not made voluntarily and are not made in a clear state of mind.
  • Polygraph: It is a device that measures and records physiological changes in body such as blood pressure, pulse rate, respiration and skin conductivity of as few instruments are stick for recording these rates while the subject or she answers the questions asked by authorities. Use of the polygraph is supported by this presumption that deceptive answers will produce physiological responses different from those associated with non-deceptive answers but in reality, no certain physiological reactions related to lying exist, making it difficult to identify specific factors that can distinguish those who are lying from those who are telling the truth. Moreover, many times, measured changes in physiological responses are not because of lying and deception but only the result of anxiety, fear, nervousness, confusion etc. Thus, Polygraph is considered an invalid means of assessing truthfulness and usually not accepted by courts.
  • Brain Mapping: This test, also known as "P 300 waves test" is basically employed to discover that whether a person is friendly with information or not, it is based on presumption that brain would generate different brainwaves in response to a known stimuli such as image, video or sound. This technique determines neurological activities by capturing brainwaves through electrodes placed on the face and neck.

Constitutional Status of Lie Detector in India
Our Constitution does not contain any specific provision regarding use of such mechanism to extract truth instead Article 20 (3) clearly provides immunity to an accused against self-incrimination by declaring that no person accused of an offence shall be compelled to be a witness against himself. This Article is based is based on the legal maxim "nemo teneteur prodre accussare seipsum", which means "No man is obliged to be a witness against himself" thus, use of Lie Detector Test during investigation is, evidently, violates the principle given under Article 20(3).

Legal Status of Lie Detectors in India
  • Code of Criminal Procedure, 1973:
    No provision related to use of lie detectors in any criminal case, have been mentioned in our criminal code too. However, Section 53(1) of CrPC does talk about medical examination by medical practitioner at request of police officer with a view to gather evidence but it does not, specifically, provides for use of such lie detecting technique in order to gather evidence. Moreover, section 161(2) says that no one is bound to answer question having tendency to expose him to criminal charge.
  • Indian Evidence Act, 1872:
    Statements obtained from lie detectors does not come under purview of definition of evidence as provided under section 3(1) of this Act so the results of polygraph examinations are not accepted as sole evidence in court though any information discovered with the help of such a consented test taken by the accused can be admitted as corroborative evidence but IEA does not directly provides provision with regard to it.

Legal Requirements to fulfill before using lie detection techniques:
National Human Right Commission has issued guidelines which have to be kept in mind before using these tests and techniques to administer the test in finer way, some of them are given below:
  • Lie Detector Test should be administered with consent of subject
  • Consent given by subject must be recorded before judicial magistrate
  • Subject must be aware that words spoken by him during test are just statement to police not confession
  • While Polygraphy results are being presented before magistrate, police will have to show to court that accused has agreed for test
  • While considering Polygraphy test, the judge will have to consider the facts such as duration of detention and manner of interrogation.

Supreme Court on Lie Detection Techniques
In case of Selvi V. State of Karnataka[2], Honorable Supreme Court clearly held that the interrogation involving above mentioned techniques can be administered only with the consent of the subject before a magistrate and no one can be forced to undergo the test involuntarily as Article 20(3) protects an individual choice between speaking and remaining silent, besides, involuntary interrogation amounts to 3rd degree methods and the court cannot permit such tests.

Furthermore, court also declared that result obtained from each of the impugned test bear a 'testimonial' character so they cannot be categorized as proper evidence, however material and other evidence derived from Polygraph interrogation can be used as evidence under section 27 of India evidence Act.

Indeed, it is true that law is a living process that gets advanced with time in terms of scientific, societal and other kinds of advancements, however, it is equally true that a country having largest democracy in world cannot compromise with fundamental rights of its citizens given by the constitution, therefore, these deception detection tests (DDTs) , that can be used as a fairly effective tools for the exposure of deception in a subject but, in no way, it should encroach upon one's right to privacy, right against self incrimination or right to life and liberty.

Besides, it is also fact that DDTs are not error free piece of evidences as many times it is not possible to discern the differences between manipulative and genuine responses accurately. Thus, in my view, acceptance of evidences gathered solely through DDTs cannot be said to be reliable and while considering this kind of evidence for any reference, the quality of evidence, its proper processing and presentation should be ensured.

Furthermore, to streamline the use and application of lie detection techniques, the parliament should enact a new legislation based on the guidelines provided by NHRC and guidelines provided in the case of Selvi vs state of Karnataka so that no innocent suffers and no culprit can escape punishment due to faulty investigation and miscarriage of justice.

  1. Polygraph. (n.d.). In Wikepedia.
  2. Sabherwal, Jasleen. Analysis of use of lie detectors in criminal justice.( January 10, 2023). Juris Centre.
  1. AIR 2010 SC 1974, (2010) 7 SCC
Written By: Mridulika Pandey, 4th Year Student Of BALLB at University Of Allahabad

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