Psychological Detection Techniques: in the view of Constitutional Law

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Due to the fact that science has overtaken the evolution of law, or at least the layperson’s understanding of it, there is an inescapable degree of complication in terms of what can be allowed as evidence in court. In India, forensic psychiatric testing is one such scientific advancement that has become an increasingly, and perhaps alarmingly, frequent word. 

Torturing a person to extract information utilising third degree procedures was popular around 2-3 decades ago. When a crime is reported to the police, it is their obligation to investigate the matter, identify the culprit, discover the facts and circumstances, and present the evidence to the court to determine whether the suspect is guilty or not. However, in today’s age, criminals have become more smart and are using cutting-edge technology to do their crimes. They don’t leave much evidence at the crime scene. The police’s employment of the third-degree approach merely serves to fabricate cases and suppress the facts. As a result, imprisonment crimes and death are on the rise. It’s a major setback for the “rule of law.” The “DDT” method is a soft option for avoiding custodial deaths and third-degree approaches (Detection of deception techniques).

Since few years, science and technology progress has accelerated, resulting in advanced tools for police officers to replace third-degree torture and aid in lie detection. It performs the task in a smooth manner. Polygraph tests, brain mapping, and narco analysis are some of the methods used in interrogation. These tests were newly created to extract information.

The investigating officers employ these psychoanalytical methods to discover the facts, observe the suspect’s conduct, and draw conclusions based on their findings. The three most common deception detection tests are polygraph, Narco analysis, and brain mapping. They play a significant role in ethical, scientific, and regulatory requirements. 

The function of forensic science in the investigation of a crime is crucial. The term “forensic” is considered as “crime solving through the use of science and the resolution of issues arising from a crime or litigation.” It is an important aspect of jurisprudence. It’s a tool for enforcing the rule of law. Forensics is the application of science to the conclusion of a crime investigation. However, because the examinees are subjected to pain and suffering throughout these tests, they can appear to be in violation of their fundamental rights. The method through which the data is extracted is also under contention, as they are not in their right mind when participating in these tests. 

This article aims at establishing the objective, need and procedure of three DDT tools namely, Narco analysis, polygraph and brain mapping. Further, it attempts to analyse these tests on the pedestals of fundamental rights thereby, establishing a conclusion. 

Narco analysis: Man induced Hypnosis

The term narco is derived from the Greek term NARKE, which means “anaesthesia”, and is now used to describe a diagnostic psychotherapeutic technique that employs psychotropic capsules to induce a state of suspension or significant reduction of sensibility, a state in which mental detail and robust related effects emerge to be exploited by the therapist. It refers to psychoanalysis that takes place in a state similar to sleep and is finished with the aid of drugs. The medications are referred to as “reality pills” or “truth serum.” Hypnosis and narcosis are combined in narco analysis. In a short period of time, the psychiatrist should obtain additional specifics of menial contents. Lie Detector Testing or Truth System Testing are other names for the Narco assessment test. In this case, the individual enters their subconscious mind with the help of the serum and speaks whatever is found in their mind. This advanced science requires two professions, law and technology, to collaborate in various situations. 

The goal of Narco analysis is to solve a person’s lie while he is employing his imagination, but only within the Narco evaluation. Because the person enters the subconscious stage, it checks and neutralises their creativity. As a result, it is assumed that the person cannot lie, and that whatever he says is genuine and spontaneous.


The narco-analysis test will be performed in the Operation Theater (OT) by a team of doctors, anaesthetists, forensic experts, OT nurses, and OT attendants. The subject, along with the other devices, will be connected to the BIS monitor. Distil water will be used to dilute one gram of sodium Pentothal to 200 mL. With the assistance of an anaesthetist, the dissolved solution is injected intravenously along with 10% dextrose. The insights made during the hypnotic trance are caught on camera. When the medicine PentothalSodium is given intravenously, the person goes through four stages:

  1. Awake stage 
  2. Trance stage 
  3. Sedative stage 
  4. Anaesthesia Stage 

A significantly lower amount of pentothal sodium is injected and kept in a trance for the duration of the inquiry to extract information about the crime under investigation. The trance state makes it easier to deal with negative emotions in a constructive way. It aids in the study and identification of unresolved events-related conflicts. It causes the person to reveal information that is normally hidden from conscious awareness. Once the medicine is no longer administered, this process stops immediately.


The following are some of the reasons why narco analysis tests are criticised:

  1. Narco analysis is not 100 percent accurate, according to Dr. B.M. Mohan, Director of FSL, Bangalore, who claims that narco analysis has a 96-97 percent complete screen rate based on his data. He believed that narco analysis should be discredited.
  2. Former director of the Tamil Nadu Forensic Science Department, Dr. P. Chandra Sekharan, compared the narco analysis test to a third-degree method of investigation and termed it unscientific.
  3. Certain subjects in the Narco analysis produced wholly false statements as a result of deception. If a person has been a drug addict or alcoholic, he or she may have a high tolerance level, as well as a false state of semi-focus and the ability to tell lies.
  4. It’s difficult to provide a certain drug dosage for a certain person because it will differ from person to person depending on the problem’s intellectual attitude and physical shape. It is stated that administering the wrong dose to the individual could result in his death.

Polygraph: Lie detection technique

The Polygraph test, often known as an instrumental assessment, examines a variety of psychological approaches and modifications in these techniques. Examiners deduce a mental state, specifically, whether or not someone is telling the truth or is lying, from the chart of such measures in response to the query on a Polygraph check, which is frequently supported by observations made during the Polygraph check. The intellectual excitation is the result of these mental phenomena. Psychologically, the character’s attempt to disguise his or her excitement is referred to as the “protection mechanism,” which stimulates the adrenal glands, which then emit the adrenaline hormone.

The term “polygraph” refers to a process that records certain physiological processes. The term polygraph refers to a test that measures body activity and graphically records variations in bodily activity. The Autonomic Nervous System (ANS) fluctuation is measured by a polygraph test. The polygraph is based on the idea that emotional factors cause changes in bodily activity. These adjustments are unintentional and automatic.Polygraphs are used to detect lying in response to a query that results in physiological changes that differ from those shown in a normal response. Changes in the respiratory system, cardiovascular system, and electro dermal system are all measured by a polygraph. The truthfulness or lying of the responses is determined by examining the graphical changes in the responses. 



Polygraph is viewed as a series of mental examinations. Blood pressure, pulse rate, respiration rate, muscular action, and skin conductivity are all measured in this study. The following tactics will be evaluated by a competent and qualified inspector:

1. as a declaration of the examiner’s emotional state;

2. The examination’s medical suitability

3. Conduct specialist assessments to become aware of overly sensitive behaviour.

4. To check exam modification query responsiveness, a query should be requested.

5. To conduct a thorough examination of case files and

6. Conduct a pre-interview and a detailed preview of questions.

As previously stated in the polygraph, three aspects of human physiology are examined:

1. Tracing with a pneumograph

2. Tracing of electrodermal pastimes

3. tracing of the cardiovascular system

Pneumograph tracing is concerned with respiratory function, while Electrodermal tracing is concerned with skin conductance or skin resistance, and cardiovascular tracing is concerned with blood volume and pulse charge. Perspiration takes a chance when a person tries to hide physiological changes such as increased or decreased blood volume, increased or decreased heart rate, and changes in breathing. If the person is telling the truth, the organs will show physiological changes that are typical of a normal sample. The check’s final result is displayed on a chart known as a polygram. After the response, there is a suppression in breathing and a rise in blood pressure, a decrease in blood strain, conduct breathing, a slowing of pulse charge, and a shift in blood circulation direction.

The examiner carefully studies the sample of arousal responses and infers the individual’s sincerity on that premise. The polygraph does not determine if the person is saying true or untrue facts. This inference or judgement is referred to as a fact diagnostic or a false fact diagnostic.


The polygraph technique of examination is criticized on the following grounds: 

(1) The check no longer determines whether the person is telling the truth or not. Only the approximate physiological changes are displayed in the test, which must be analysed by a professional.

(2) No technology is concerned with the inquiry, and it completely relies on deception and the tester’s information.

(3) An individual who can manage his feelings to a great level can still tell a lie; nevertheless, if an individual has control over himself through yoga practise or any other means, this check is certain to fail.

(4) Many innocent and straightforward persons appear to be tense when confronted with police interrogation circumstances. This anxiety may arise for a variety of reasons, including being tense as a result of the crime, or the fear that his or her previous behaviour may be revealed to the authorities, which isn’t always related to the current offence. 

Brain Mapping

It’s a brain mapping test that reveals ‘guilty knowledge.’ The brain-mapping test is used to evaluate the suspect’s behaviour and to back up the police officers’ observation and the suspect’s statements. During the tests, forensic professionals use cutting-edge technology to see if a suspect’s brain recognises items from the crime scene that an innocent suspect would not be aware of. 

In a nutshell, specialists claim that the brain fingerprinting test, also known as the brain-mapping test, compares information stored in the brain to information from the crime scene. According to studies, an innocent suspect’s brain would not have stored or recorded certain facts that a perpetrator’s brain would have saved or recorded.


  1. This information is acquired by measuring the bio electrical activity of the brain. While processing the information connected to the crime, the activity of the brain is measured using multi-channel electrodes implanted over the individual’s head. P300 wave test is another name for this procedure.
  2. The activity of neurons is activated when a subject is exposed to a stimuli connected to the crime under investigation, resulting in positive reactions if the individual has truly participated in the crime.
  3. The test detects a P300 wave, which is an Event Related Brain Potential (ERP) released by the brain following the processing of a stimulus. ERP is a metric that measures cognitive mental activity. The examiner can determine if the subject recognises the stimulus in which he or she actively participated or witnessed by measuring cognitive mental activity.

Determining the probes’ subject familiarity aids in the detection of deception, sincere involvement, or the gathering of useful information. The test was also supported on the grounds that it was completely noninvasive. The purpose of the examination is to determine whether or not the accused has knowledge of the offence.


The Brain mapping forensic science technique has been criticized on the following grounds: 

  1. Some experts have disputed statements made in scientific publications and the public press based on brain imaging, such as the finding of “the portion of the brain responsible” for emotions, musical ability, or a specific memory.
  2. Many mapping approaches have a low resolution, despite the fact that a single voxel can contain hundreds of thousands of neurons. Because many functions involve several areas of the brain, this type of claim is likely to be both unverifiable with the technology employed and based on an inaccurate assumption about how brain functions are split in general.

Evidentiary Value of Forensic Psychoanalytic techniques

The Indian Law of Evidence does not take a position on the admissibility of information obtained by a psycho-analysis test. However, there are some sections that define the stance of this law in terms of technology. 

The definition of ‘evidence’ under section 3 of the Indian Evidence Act, 1872 is as under:

“Evidence” means and includes

(1) All statements which the Court permits or requires to be made before it by witnesses, in relation to matters of act under inquiry; such statements are called oral evidence;

(2) All statements including electronic records produced for the inspection of the Court; Such statements are called documentary evidence.

The question is therefore whether or whether the results of the narco-analysis test, polygraphy and the brain mapping can and should be regarded as evidence. In the event of even the slightest indication of coercion, intimidation, or any other type of influence, such statements would be excluded from being accepted as evidence and rendered useless, according to a combined reading of Sections 24 to 27 of the Indian Evidence Act.

Induced, threatened, or promised confessions are inadmissible under Section 24 of the Indian Evidence Act. When an accused is subjected to a narco-analysis test, he loses control of his mind and is forced to answer questions against his will. Such confessions are impliedly inadmissible in a court of law. The confessions made in presence of the agency conducting the procedure and the police are also hit by Section 25 of the Act.

In the case of Selvi and Ors. v. State of Karnataka and Anr., honourable Supreme Court held that As a result of psychoanalytical testing, an individual, whether an accused or a witness, cannot be forced to endure any of the aforementioned techniques in order to expose him to any penalties or other consequences. There can be no reasonable technical reason for invading a person’s mental privacy. Because of their limitations, the results inferred from the use of these methodologies are also in conflict with the principle of “right to a fair trial.”

Interestingly, it should be noted that the Court did leave some scope for voluntary administration of the impugned techniques with regards to criminal investigation with proper safeguards in place. Even in such instances, the test results by themselves cannot be admitted as standalone evidence, reason being lack of control of the subject over his responses during the test. However, any information or material that is subsequently discovered with the help of voluntary administered test results can be admitted, in accordance with Section 27 of the Evidence Act, 1872.

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The techniques of pshyco-analysis have proved to be valuable and profoundly effective in sensational cases like the Aarushi Talwar murder case, the Nithari killings case, the Telgi scam, and the Mumbai Bomb Blasts case. 

Constitutional Validity of Psychoanalytic techniques

In the case of Rojo George v. Deputy Superintendent of Police, the Kerala High Court allowed the Narco-analysis test, stating that criminals’ strategies for committing crimes are exceedingly complex and modern in today’s world. It’s possible that traditional inquiry won’t yield any results.As a result, scientific tests such as polygraphs, brain mapping, and narco-analysis are now being used in the case investigation. When such a test is carried out under the rigorous supervision of an expert, it is impossible to claim that any fundamental rights granted to Indian citizens have been violated.

In the case of Santokben Sharma bhai Jadeja v. State of Gujarat, the court ruled that “Narco analysis tests are conducted under the supervision of doctors and adequate care is taken and agreement is obtained, with the observation of the accused’s physical and mental state.” It was decided that the protection afforded under Article 20(3) could not be claimed to have been infringed simply because a  Pshyco-analytic Test was performed. Furthermore, the bar under Article 20(3) applies if the prosecuting agency uses the statement made as part of the test as evidence at any point and if it incriminates and implicates the person who made it. It also found that conducting/performing the aforementioned tests is a component of the inquiry and is required for the investigation, and that the accused’s consent is not required. 

The Maharashtra High Court in the case of Ramachandra  Reddy  v. State  of  Maharashtra, held as follows: 

“It must also be viewed in the context of other equally significant Constitutional provisions. Clause (1) of Article 51(A), which was introduced to the Constitution by subsequent amendment, states that it shall be the duty of the State, and that the responsibility cannot be adequately performed by the State if large protection is unduly spelled out from other provisions like Article 20(3)”. The state’s sole prerogative is to prevent crime, and it is also the state’s responsibility to punish the crime if it is proven. Restraints on these obligations can only be imposed in severe instances where the safeguarding of fundamental rights outweighs the fundamental duty imposed on the state.

In the case of State of Andhra Pradesh v. Inapuri Padma, the court upheld the constitutionality of brain mapping and polygraph tests, reasoning that unless the criminals are apprehended using scientific methods, there is a risk that they will believe there is no agency that can bring them to justice and hold them accountable for their crimes. By using Brain Mapping, Narco Analysis, and Polygraph Tests, it is impossible to know what statement the person undergoing the test will make, whether incriminatory or not. As a result, the protection provided under Article 20(3) against coerced testimony does not apply to these tests.

In Shailender Sharma v. State, the Delhi High Court upheld the validity of the psychoanalytic techniques, stating that, in light of the rising number of crimes against society, it is necessary to consider the needs of society as a whole and the need for a thorough investigation while ensuring that constitutional rights are not violated. The court stated that because the Narcoanalysis Test is a step-in-the-right-direction of an investigation, it has no constitutional flaws. When an investigating agency is short on critical leads, Narco Analysis can help. This is especially true in instances involving terrorism and its connected cases, murder plot, and other serious felonies.

As already mentioned, in Selvi and Ors. v. State of Karnataka and Anr., a bench of Justices of India KG Balakrsihanan, R.V. Raveendran, and J.M. Panchal holds that no individual should be forcibly subjected to these techniques, whether in the context of a criminal investigation or otherwise, but the bench does leave room for voluntary administration of these techniques. 

Although  the  High  Court’s  mostly  decided  in  favor  of the constitutionality  of involuntary  administration  of  the  tests,  they  had  not  analyzed  the  limitations  of  the  tests. This  was  dealt with in  detail  by  the  Supreme  Court  of  India  in this case. 

Furthermore, the court addressed two important concerns in considering the legitimacy of involuntary administration of the tests and the admissibility of the information obtained:

firstly  whether  the  tests  amounted  to  violation  of  right  against  self-incrimination  and  secondly,  whether  it  amounted  to  violation  of  the  fundamental  right  to freedom   of  life   and   liberty   under   Article   21   of   the   Indian   Constitution, certain misconceptions  were created  following the  judgment  in the  Apex  court. The court held that Indian constitution protects the individual’s right against self incrimination and article 20(3) gives the right to the accused to not be a compelled witness against himself. The main idea behind article 20(3) is to protect accused against self incrimination and to save the accused from becoming an evidence against himself. 

Because the subject is not obliged to make a vocal answer, the information obtained during a polygraph test; Brain Mapping Test cannot be equated with testimonial compulsion and thus falls beyond the scope of Article 20(3). The bar of article 20(3) does not apply to a verbal revelation produced during Narco-analysis since the inculpatory or exculpatory character of the revelation is unknown at the time of the test. In the Selvi case, the Supreme Court underlined and defined the prohibition under Article 20(3), concluding that scientific methods fill in gaps and enhance a weak inquiry chain. A situation in which a testimonial response is used to compare with facts already known to the investigator is essentially different from a situation in which a testimonial response is used to compare with facts already known to the investigator.


Polygraph tests, brain mapping, and Narco analysis have all been subjected to several criticisms, and it is still unclear to what degree they are valid. Modern-day criminals utilise technology to further their criminal operations, hence it is necessary for prosecutors, police, and courts to seek assistance from the scientific and technological community in delivering criminal justice. 

The legal procedures, evidence norms, and institutional infrastructure that were in place many years ago are now insufficient to meet the needs of the scientific age.The absence of a national policy is the most significant flaw in the administration of criminal justice.

It is the court’s responsibility to ensure that those who are guilty are punished and those who are innocent are free. There is no breach of individual rights because both are public tasks, and these tests aid in the identification of victims in many key circumstances and can be used to combat custodial fatalities. These tests must be utilised to find the accused and interview the suspects in high-profile cases. These approaches have the potential to become an alternative to third-degree physical torture in police custody of investigation, assisting in the prosecution of modern-day criminals. 

The central government should also implement a national policy to ensure that individual rights are not violated, as stated in the supreme court’s decision in the case of D.K Basu v. state of West Bengal, that there is an urgent need to develop scientific technical methods for interrogating accused in custodial deaths and torture is nothing more than a blow to the rule of law.