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12. The control-question (CQ) technique is the most commonly used one and its procedure as well as scoring system has been described in the materials submitted on behalf of CBI. The test consists of control questions and relevant questions. The control questions are irrelevant to the facts being investigated but they are intended to provoke distinct physiological responses, as well as false denials. These responses are compared with the responses triggered by the relevant questions. Theoretically, a truthful subject will show greater physiological responses to the control questions which he/she has reluctantly answered falsely, than to the relevant questions, which the subject can easily answer truthfully. Conversely, a deceptive subject will show greater physiological responses while giving false answers to relevant questions in comparison to the responses triggered by false answers to control questions. In other words, a guilty subject is more likely to be concerned with lying about the relevant facts as opposed to lying about other facts in general. An innocent subject will have no trouble in truthfully answering the relevant questions but will have trouble in giving false answers to control questions. The scoring of the tests is done by assigning a numerical value, positive or negative, to each response given by the subject. After accounting for all the numbers, the result is compared to a standard numerical value to indicate the overall level of deception. The net conclusion may indicate truth, deception or uncertainty.

20. A Working Party of the British Psychological Society (BPS) also came to a similar conclusion in a study published in 2004. The key finding is reproduced below, [Cited from: A Review of the current scientific status and fields of application of polygraph deception detection - Final Report (6 October, 2004) from The British Psychological Society (BPS) Working Party at p. 10]:

"A polygraph is sometimes called a lie detector, but this term is misleading. A polygraph does not detect lies, but only arousal which is assumed to accompany telling a lie. Polygraph examiners have no other option than to measure deception in such an indirect way, as a pattern of physiological activity directly related to lying does not exist (Saxe, 1991). Three of the four most popular lie detection procedures using the polygraph (Relevant/Irrelevant Test, Control Question Test and Directed Lie Test, ...) are built upon the premise that, while answering so-called `relevant' questions, liars will be more aroused than while answering so-called `control' questions, due to a fear of detection (fear of getting caught lying). This premise is somewhat naive as truth tellers may also be more aroused when answering the relevant questions, particularly: (i) when these relevant questions are emotion evoking questions (e.g. when an innocent man, suspected of murdering his beloved wife, is asked questions about his wife in a polygraph test, the memory of his late wife might re-awaken his strong feelings about her); and (ii) when the innocent examinee experiences fear, which may occur, for example, when the person is afraid that his or her honest answers will not be believed by the polygraph examiner. The other popular test (Guilty Knowledge Test, ...) is built upon the premise that guilty examinees will be more aroused concerning certain information due to different orienting reactions, that is, they will show enhanced orienting responses when recognising crucial details of a crime. This premise has strong support in psychophysiological research (Fiedler, Schmidt & Stahl, 2002)."

84. Not only does an accused person have the right to refuse to answer any question that may lead to incrimination, there is also a rule against adverse inferences being drawn from the fact of his/her silence. At the trial stage, Section 313(3) of the CrPC places a crucial limitation on the power of the court to put questions to the accused so that the latter may explain any circumstances appearing in the evidence against him. It lays down that the accused shall not render himself/herself liable to punishment by refusing to answer such questions, or by giving false answers to them. Further, Proviso (b) to Section 315(1) of CrPC mandates that even though an accused person can be a competent witness for the defence, his/her failure to give evidence shall not be made the subject of any comment by any of the parties or the court or give rise to any presumption against himself or any person charged together with him at the trial. It is evident that Section 161(2), CrPC enables a person to choose silence in response to questioning by a police officer during the stage of investigation, and as per the scheme of Section 313(3) and Proviso (b) to Section 315(1) of the same code, adverse inferences cannot be drawn on account of the accused person's silence during the trial stage. Historical origins of the `right against self-incrimination'

"132. Witness not excused from answering on ground that answer will criminate. - A witness shall not be excused from answering any question as to any matter relevant to the matter in issue in any suit or in any civil or criminal proceeding, upon the ground that the answer to such question will criminate, or may tend directly or indirectly to criminate, such witness, or that it will expose, or tend directly or indirectly to expose, such witness to a penalty or forfeiture of any kind.