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The article is written by Nikhil Thakur from Manav Rachna University. In this article, the author has briefly explained the constitutional validity of the deception detection test (DDTs).


The deception detection tests (DDT) such as polygraph, narco-analysis and brain-mapping have imperative clinical, logical, moral and legitimate suggestions. The DDTs are valuable to know the concealed data related to wrongdoing. This data, which is known as it were to self, is in some cases pivotal for criminal examination. 

The DDTs have been utilized broadly by examining organizations or forensic experts. Besides this, DDTs are moreover utilized to pick up a lead within the case, or in cases when the potential witness is incapable to gather data, it is additionally utilized in some cases on the suspect, the utilization of DDTs on suspects can have different impacts. In a point of interest judgment, the Apex Court of India has clearly expressed that DDTs cannot be managed without assent.

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Classification of DDTs

Predominantly, there are three categories within the Deception Detection Test, that are:

  1. Narco-analysis test,
  2. Polygraph test, and 
  3. Brain mapping test.

Narco-analysis test

The term narco-analysis was coined by Horseley. Narco-analysis is inferred from the Greek word narkç (meaning “anaesthesia” or “torpor”) and is utilized to portray a demonstrative and psychotherapeutic procedure that uses psychotropic drugs, especially barbiturates, to initiate a daze in which mental components with strongly related influences come to the surface, where they can be misused by the specialist. 

Narco examination includes the infusion of a sedate, sodium pentothal, which actuates a trancelike or calmed state in which the subject’s creative ability is neutralized, and they are anticipated to unveil genuine data. 

The medicate (sodium pentothal) alluded to as a “truth serum”, is utilized in bigger dosages as anaesthesia amid surgery, and is said to have been utilized during World War II for insights operations. Basically, within the sleep-inducing arrangement, the subject gets to be less hindered and is more likely to uncover data, which would usually not be uncovered within the cognizant state. The experts while examining the suspect may uncover all his/her fantasies, individual wishes, impulses, instinctual drive, figments, daydreams, clashes, misinterpretations, etc.

The loophole of this method is that some people can bloodstream hold their capacity to misdirect indeed within the trancelike state, whereas others can end up amazingly suggestible to addressing.

Narco-analysis “without consent” raises certain issues such as:

  1. A physical ambush on the body by giving infusions additional excruciating boosts such as slapping, squeezing, pushing, hitting, shaking the body and so forth to wake an individual from a hypnotic state to reply to the questions.
  2. Mental attack through the effect of the infusion of narco drugs.
  3. Off-base dosage can send the subject into a coma or indeed result in passing off or death.
  4. Further, this method is highly criticized by therapeutic society and consider it as not adequate in the treatment of psychiatric issues.

During the Telgi scam, the use of narcoanalysis came under the scanner, and then it was used in the Aarushi murder investigation.

Polygraph test

Typically, also called a lie detector test, but this term could be a misnomer. The hypothesis behind polygraph tests is that a blameworthy subject is more likely to be concerned with lying around the pertinent truths than the wrongdoing, which in turn produces a hyper-arousal state which is picked up by an individual trained in perusing polygraph results. The polygraph test is conducted in three phases- a pretest interview, chart recording and diagnosis.

It may be a strategy that measures and records a few physiological pointers such as blood weight, beat, breath, and skin conductivity whereas an individual is inquired and required to answer an arrangement of questions;

  1. This test is based on the suspicion that physiological reactions are activated when an individual is lying.
  2. Numerical esteem is relegated to each reaction to conclude whether the individual is telling the truth, is beguiling, or is uncertain. 

A test comparable to a polygraph was first executed in the 19th century by an Italian criminologist Cesare Lombroso, who utilized a machine to determine changes within the blood pressure of criminal suspects amid cross-examination. Comparable gadgets along these lines were made by the American clinician William Marston in 1914, and by the California police officer John Larson in 1921.

In the polygraph technique, instruments like cardio-cuffs or delicate cathodes are connected to an individual, and factors such as blood weight, beat, breath, alteration in sweat gland movement, bloodstream, etc., are measured as questions are put to them.

The polygraph test was among the primary logical tests to be utilized by the investigators. It was Keeler who further refined the polygraph machine by including a psycho-galvanometer to record the electrical resistance of the skin.

Reliability of Polygraph

  1. The primary issue connected to the polygraph test is that it cannot differentiate between the changes that have taken place in the body whether it is by way of a lie or something else.
  2. Other factors just like the environment where the test is conducted are how the questions of the exploring officers were and what tone he has used, moreover play a noteworthy part in influencing the reading test.

Polygraphed test results can be beaten by people with the capacity to smother the excitement reaction, such capacity is picked up by those who perform unwinding works out like yoga or meditation.

Brain-mapping test

It measures the changes in the electrical field potentials produced by the sum of the neuronal activity in the brain by means of electrodes placed on the surface of the skin covering the head and face. This means it is based on the finding that the brain produces an interesting brain-wave design when an individual experiences a commonplace stimulus. 

A commonly utilized strategy in India is called the Brain Electrical Activation Profile test, moreover known as the ‘P300 Waves test’.

In brain-mapping, sensors are connected to the suspect’s head and a person is made to sit before a computer screen. The suspect is at that point made to see pictures or listen to sounds. The sensors screen electrical movement within the brain and enlist certain waves which are produced as if on the off-chance that the suspect has any association with the same.

Reliability of brain mapping

  1. In case a person was presented at the crime scene or has ambiguously taken note of the same, sometimes the said person may be brought under suspicion using this technique.
  2. Such a method might not be utilized as a strategy to indict somebody but can be utilized as a strategy to demonstrate one’s guilt.

Constitutional validity

In India, the use of deception detecting tests (DDTs) has been questioned in courts. The main argument against it is the infringement of the fundamental right under Article 20(3) and Article 21 of the Indian Constitution, which provides for a privilege against self-incrimination and the right to health and privacy, respectively.

In a landmark judgment of Selvi & Ors vs State of Karnataka & Anr (2010), a Supreme Court bench comprising the then Chief Justice of India K G Balakrishnan and Judges R V Raveendran and J M Panchal ruled that no lie detector tests ought to be managed “except on the premise of assent of the accused”. Those who volunteer must have to get to an attorney and have the physical, passionate, and legitimate suggestions of the test clarified to them by the police and the legal counsellor.

Earlier in the case of Dinesh Dalmia v. State by Spe, CBI 2006, the Madras High court ruled that in case the accused fails to participate within the examination, at that point scientific methods can be utilized to discover the truth encompassing the wrongdoing. In the instant case, the Hon’ble Madras High Court resorted to an implied perspective of legitimizing the DDTs.

A comparable position was taken by the Court in Sh. Shailendra Sharma Vs State & Another 2008 and it was held that such scientific methods help with the examination and can be of great utility. Concerning constitutional legitimacy, the court is of the conclusion that by utilization of these scientific methods, no constitutional infirmity emerges. Such methods help within the examination, and in case any incriminatory explanation comes to the surface amid the examination, indeed at that point, the indictment cannot depend on that articulation and the same cannot be delivered as proof.

Violation of the individual rights of self-being

In case an individual is not willing to assent, it is being accepted or presumed by the people that he is not participating in the examination and might have committed or is guilty of the offence. But DDT has certain results which are unscrupulous as well as unlawful that are or may be violative of the individual rights of Self being or not to be questioned if he refuses the DDT of a person.

Violation of the right to be silent

Till the time a test is conducted voluntarily upon the suspect, there shall be no violation of the right to remain silent, but in case anyone is pressurised or forced to go through the deception detection test shall amount to a violation of the right to be silent and shall lead to an infringement of Article 20(3) of the Indian Constitution.


It is a well-settled common law tenet that each denounced individual is assumed innocent unless demonstrated guilty and it is for the prosecution to demonstrate or prove the blame of the accused and in the process, the accused cannot be compelled to make a self-incriminating explanation.

In Nandini Sathpathy vs P.L. Dani (1978), the Supreme Court held that no one can forcibly extract statements from the accused, who has the right to remain silent during interrogation or investigation.

In the Selvi vs State of Karnataka & Anr. (2010), the Supreme Court ruled that no lie detector test ought to be managed without the assent of the accused. Moreover, the court further observed the following things: 

  1. Further, those who volunteer must go to the attorney and have the physical, emotional, and lawful suggestions of the test clarified to them by police and the lawyer.
  2. The results of the tests cannot be considered to be “confessions”, but any data or material subsequently found with the assistance of such a voluntarily-taken test can be conceded as a piece of evidence.
  3. The Supreme Court cited Article 20 (3) of the Indian Constitution or right against self-incrimination and held that no person can be compelled to be a witness in his case.

In the D.K. Basu vs. State of West Bengal (1997), the Supreme Court ruled that an involuntary administration of the polygraph and narcosis test shall amount to brutal, inhuman, and degrading treatment within the setting of Article 21 or the right to Life and Liberty.

Violation of the right to health

DDTs have great repercussions on the body of the person being tested. A person is hypnotised to ask questions and that is accompanied by slapping, squeezing, pushing, hitting, shaking the body that has mental as well as physical repercussions. Further, higher dosages are administered during the test that have the capability of causing the person to move into a coma. These issues raise a concern over the right to health which is held as pivotal by few Conventions and judicial decisions.

Article 25 of the Universal Declaration of Human Rights, 1948 states “that everyone has the right to a standard of living adequate for the health, and wellbeing of himself and his family”.

The Supreme Court of India in Urjit Singh v. The State of Punjab (1996) concluded that law is in this manner well settled and that the right to wellbeing is a necessary portion of life ensured under Article 21 of the Indian Constitution.

Violation of the right to privacy

In Selvi and Ors Vs State of Karnataka (2010), the Supreme Court held that the utilization of narco examination, brain-mapping and polygraph tests on accused, suspects and witnesses without their assent, is unlawful and an infringement of the right to privacy.


These strategies cannot be utilized as strong proof or confessions due to their constrained unwavering quality and inefficient logical proofs. In any case, they can be utilized as valuable instruments to unravel complicated cases as investigative instruments. The government shall empower the use of scientific methods but shall come up with strict rules for their utilization in a conventional, and consensual way.

With the up-gradation, innovative changes are inescapable. Science and reason are bound to thrive, but will it develop towards advancement or devastation are still one of the major issues. With these scientific advancements, the impact on other areas is apparent, and in a field like law that touches nearly every circle of a citizen, it cannot stay protected.

The issue is whether we require to think past the Constitution for genuine equity or the Constitution alone is the equity in genuine senses.”


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