Analysis of the Use of Lie Detectors in Criminal Justice

The therapeutic, scientific, moral, and legal ramifications of deception detection tests (DDT) like the polygraph, narco-analysis, and brain mapping are significant. The DDTs are helpful for discovering hidden information about crimes. Sometimes, the only person who knows this information is the subject of a criminal investigation. The investigative agencies frequently employ DDTs. However, the information-extracting organisations are aware that it cannot be used as evidence in the courtroom. They have disputed the claim that it is less dangerous than some investigators’ use of “third degree procedures.” Here, it is asserted that employing these allegedly “scientific processes” will immediately assist the investigating agencies in gathering evidence, increasing the rate of prosecution of the guilty and the rate of acquittal of the innocent3. Without any solid supporting data, these methods have recently been marketed as being more precise and superior than all others. DDTs cannot be administered without consent, the Indian Supreme Court has ruled in a landmark decision.


Many complex techniques were employed in ancient societies to identify liars. These techniques primarily used torture to elicit information. Boiling water was employed as a lie detector during the middle ages. The general consensus at the time was that innocent, truthful people would fare better under such circumstances than liars. Cesare Lombroso created a device to gauge blood pressure changes for police cases in 1895. Later, in 1904, a Vittorio Benussi invention was made use of to gauge breathing. Last but not least, William Martson’s study of the blood pressure of German POWs revealed a high correlation between a person’s blood pressure and lying. It is stated that a test of this kind was the first done in the 19th Century by Italian criminologist Cesare Lombroso. Marston has referred to himself as the “father of the polygraph” despite significant contributions from his forebears. He pushed the use of the decide in courts and was a fervent supporter of it. He then wrote a book named “The Lie Detector Test” in 1938 in which he discussed the instrument’s theory and application. Dr. John Augustus Larson created a gadget in 1921 that could measure both galvanic skin reaction and blood pressure. The Berkeley Police Department was the first to employ his technology for law enforcement. Leonarde Keeler worked on the same device for longer. In 1939, he improved the apparatus, made it portable, and included the galvanic skin reaction. The FBI reportedly acquired this upgraded version and used it as the model for the current polygraph. Similar to Leonarde Keeler’s polygraph, numerous more devices were developed. These included the Darrow Behavior Research Photo-polygraph, which was created specifically for behavioural research studies, and the Berkeley Psychograph, invented by CD Lee in 1936 to record blood pressure, pulse, and respiration. John E. Reid created a gadget in 1945 that could track the muscular activity that preceded variations in blood pressure. He asserted that capturing muscular activity in addition to regular blood pressure measurements would increase accuracy. -pulse-respiration.


Over time, the polygraph exam has come to be associated with lie detection, according to many people. This is untrue, though. Polygraph, narcoanalysis, and brain mapping are the three forms of lie detector tests utilised in criminal investigations. To induce a subject to reveal the truth, each of these tests uses a different strategy.


The narcoanalysis test includes giving a subject a substance that causes them to experience various phases of anaesthesia. In the hypnotic stage, the subject is a little less conscious and might divulge things that he wouldn’t normally divulge consciously. This method has been around since World War II [12]. The main flaw with this method is that many people can continue to be deceptive when under hypnosis, which means they can still tell lies while under hypnosis. Contrarily, many people have a tendency to behave in a highly suggestive manner when questioned. The use of drugs on the subject in no way ensures that only the truth will be said, as claims made while under hypnosis are not necessarily true. Without consent, the narcoanalysis test raises two major concerns: [13] 1. The individual is subjected to physical abuse by being given injections, which may have further negative effects. Additionally, there are numerous painful stimuli that are applied, such as body shaking, pushing, punching, pinching, etc. 2. Mental assault happens because the investigators are tapping into the subject’s head and reading his thoughts while he is under hypnosis throughout the exam, which also raises a lot of privacy issues.


A polygraph is a device or process that measures and records several physiological indicators while a person is asked and responds to a series of questions, though it is frequently incorrectly referred to as a lie detector test. These physiological indicators include blood pressure, pulse, respiration, and skin conductivity. Although there are no specific physiological reactions linked to lying, it can be challenging to identify factors that distinguish those who are lying from those who are telling the truth. This is due to the misconception that deceptive answers will result in physiological responses that can be distinguished from those associated with non-deceptive answers, which is the basis for the use of the polygraph. The lie detector, which has been used in police interrogations and investigations since 1924, is still debatable among psychologists and not usually accepted by the courts.

The first attempt to create a device that can spot lies was quite straightforward. The initial device was designed so that it could only identify changes in the subject’s blood pressure. John Reid, a scientist, refined the tool and provided the method for conducting the test successfully. The polygraphy machine improved and evolved over time, becoming more versatile and dependable. Currently, compared to other techniques, it is more practical and reliable in detecting lies.


The brain mapping test captures brainwaves using electrodes placed on the face and neck to determine a person’s neurological activity. The test is based on the hypothesis that the brain would generate distinctively different brainwaves in response to a known stimuli, such as an image or sound. The Brain Electrical Activation Profile Test is the name of the brain mapping technique utilised in India (P300 Waves Test). In this exam, the subject is exposed to several visual or auditory stimuli that are pertinent to the problem being looked into along with other unrelated words and images. The fundamental idea is that, in the event of a guilty suspect, exposure to specific investigative “probes” will result in the production of the P300 wave, which will be detected by the lie detector. For instance, if the test finds that a witness to a murder was aware with the details surrounding the crime, the witness may be charged as an accused.


The psychosomatic interaction is a psychological theory that underlies how the exam functions. The theory focuses on the slight physical alterations that take place in a human body. A few examples of the alterations include variations in body temperature, galvanic skin resistance, muscle pressure, blood pressure or pulse rate, and respiration, such as heavy breathing. When someone lies or makes up a statement, they tend to keep back their emotions out of fear of being discovered, which causes mental instability. All of these responses cause physical and psychological changes in that person.

The polygraphy/lie detector device captures the alterations occurring in the subject’s body when they are being interrogated. It documents changes in things like abdominal respiration, Galvanic skin resistance, blood pressure and pulse rate variations, as well as a few other things. The subject’s muscle activity is also captured by the new polygraphy device model.

The suspect who is being questioned has the lie detector device connected as follows:

• Two pneumograph tubes are fastened around the subject’s chest and belly, respectively, to record any changes in the subject’s breathing patterns while he is being questioned.

• Electrodes are placed to his fingers (index or ring finger), through which a mild electric current is administered in order to detect the galvanic skin reflex. • A normal blood pressure cuff is affixed to his upper arm. The chair the person is seated on is used to gauge their body pressure and movements. The chair is constructed in this manner.

The polygraphy expert—also known as an examiner—asks the questions. A chart is used to track the subject’s bodily changes over the course of the exam. All the information needed for the subject’s interrogation should be provided to the examiner. There are a few factors that must be taken into account for the test to yield better results. It should be a quiet environment in the room where the test is administered. There shouldn’t be many people in the room. In the room, there should only be the subject, the polygraphy professional, and the case manager. Simple and concise questions will be offered during the test, and the respondent will need to react by answering yes or no. The polygraphy professional has a limited number of interrogation techniques for improved test outcomes. It is simpler to conduct a polygraphy questioning session than to analyse the polygraphy chart. The challenging aspect of this work is analysing a polygraphy chart. The final result is provided when the examiner has reviewed the chart. Does the subject speak the truth?


The National Human Rights Commission has published instructions regarding the administration of polygraph tests to suspects in letter number. 117/8/97-8 dated 11/01/2000. The standards that follow were created to ensure that subjects’ human rights would not be violated while being subjected to the polygraphy exam.

• The subject, who is the accused, must provide their consent before the Lie Detector/Polygraphy Test may be conducted. The subject should have the choice of participating in a polygraphy test or not.

• The subject should be aware of the test’s legal ramifications when he consents to having a polygraph or lie detector test performed on him and agrees to the test. He should receive the necessary information regarding the test from the police and his attorney.

When the polygraphy results are presented to the Magistrate during the hearing, the police must demonstrate to the court that the accused has consented for the test. The subject’s consent must be recorded before a judicial magistrate. And the attorney has given these documents to the judge.

• The suspect who has been interrogated should also be aware and understand that the words he used during the polygraph test are only comments he gave to the police, not confessions.

• The judge will take into account information like the length of the accused’s incarceration and the manner in which the questioning was conducted while deciding whether to order a polygraph test.

Following a 1997 petition from Shri Indra P. Choudhry, the national human rights commission created these rules. The police took the petitioner, subjected him to traumatising treatment, and afterwards gave him a polygraph test. He gave consent for the polygraph test to be done on him, and was not fully awake during the interview. The commission developed these guidelines for a better manner to administer this test after taking all of those factors into account. Given that the test concerns psychological behaviour in humans. The findings of the test will be inaccurate and may be unfairly utilised against the accused if the procedure is not followed correctly.


The polygraphy exam is one of the new strategies the police have chosen to speed up the investigation process, as we have already described. The polygraph examination is regarded as a deception detection test. New techniques like narco-analysis and brain-mapping are also included in the DDT. The polygraphy test doesn’t harm the accused and aids in more accurate investigation, making these modern techniques less violent than older ones like third degree questioning. However, these modern approaches of inquiry and questioning, particularly the polygraph exam, mostly focus on getting the accused to divulge information that could be used against him. In other words, the accused is voluntarily disclosing material that could be used against him in a legal proceeding. A person cannot testify against themselves, as stated in Article 21(3) of the Indian Constitution. The polygraphy test findings contradict this law. Thus, in a court of law, this cannot be used as evidence. In order to give the polygraphy exam without breaching Article 21 of the Indian Constitution, which states that every person has the right to personal liberty and privacy, the national human rights commission has established recommendations. Before these regulations, polygraphy tests were not carried out properly, such as when the accused was coerced into taking the test or when the accused was questioned in fear. As a result, the test results may not have been accurate or genuine, and the procedure also infringes on the individual’s right to privacy. However, there have been instances where the test-conducting organizations have adhered to the NHRC’s standards even after they were published. Additionally, according to the scientific community, the polygraphy exam might not be accurate in some circumstances. Because even if the accused or subject being questioned is innocent, his fear of the questioning process and environment, or any other reason, could lead him to panic and create an erroneous reading on the chart. It results in the punishment of an innocent person who did not commit a crime.

Case Analysis

Rojo George v/s Deputy Superintendent of Police
Facts: The suspect argued that the suggested narco-analysis test was particularly troublesome because it was carried out after giving sodium pentathlon, which has a negative effect on the central nervous system and lowers heart rate and blood pressure. One Krishna Pillai admitted to committing the crime in the case. However, the police are not willing to look into whether or not that confession is true. Although the petitioner gave the investigating agency her full cooperation during the polygraph and brain mapping tests, the agency was unable to gather any evidence. The right dosage of a drug to be provided to a subject is further claimed to be extremely difficult to calculate because it depends on the subject’s age, sex, physical constitution, and mental attitude and will power.

Issue: The recording of a person’s statement while they are undergoing a narcotics analysis is said to constitute testimonial coercion and to violate Article 20(3) of the Constitution. The immunity stated in Article 20(3) does not apply to providing blood samples or exhibiting one’s body under compulsion.

Ratio: In the court’s opinion, as narco-analysis is also a scientific test carried out by a team of scientists and won’t amount to a police interrogation in a jail or prison, the same concept should also apply to it. Consequently, when permitting the narco analysis test According to the court, criminals have started using very advanced and contemporary ways to commit crimes today. Therefore, the traditional approach to investigating and interviewing offenders will not be effective for finding a solution, necessitating the use of fresh methods like polygraphs, brain mapping, and narco analysis.

Held: The court in this instance concluded that narco-analysis is a scientific test carried out by subject-matter experts after taking all reasonable safety precautions. However, such a negative reaction could occur when any medicine given by a contemporary medicine doctor is taken. Therefore, using these approaches to conduct research cannot be stopped just because there is a remote chance of an undesirable effect.

KM. Seema Azad v/s State of U.P. 2013

Facts: Vijaysen Yadav, the primary suspect in the murder and disappearance of Faizabad law student Shashi, has undergone polygraph and narco-analysis testing in the case, which is also known as the Shashi murder case. Anand Sen, the current BSP MLA, was found guilty in this case of killing Shashi, a law student from Faridabad.

The purpose of the test: On Friday, Faizabad Chief Judicial Magistrate Shailesh Tiwari gave the police permission to carry out the tests at Bangalore’s Central Forensic Laboratory. Vijay Sen (co-accused) said during his polygraph and drug analysis tests that the then-minister had illicit affairs with Shashi, who finally became pregnant. According to Anand Sen, who documented the information in his analysis, Vijay was requested to kill her when Anand learned about it. In his trance-like performance, Vijay Sen even disclosed that Anand had contacted him after the aforementioned occurrence and said that he had forced the woman into a canal, strangled her with his own hands, and then dumped her body in the canal alone. Phone calls between Anand and Vijay Sen from the scene of Shashi’s murder helped to further substantiate this.

Held: Anand Sen, a minister in Mayawati’s cabinet at the time, was detained by police based on Vijay’s claims obtained through narcoanalysis and a polygraph test. He is still being held in custody, and the Allahabad High Court is considering a bail application.

Selvi Murugeshan v/s State of Maharashtra

Held: Anand Sen, a minister in Mayawati’s cabinet at the time, was detained by police based on Vijay’s claims obtained through narcoanalysis and a polygraph test. He is still being held in custody, and the Allahabad High Court is considering a bail application.

Problem: In this high-profile case, the investigating agency asked the court to order a drug test. In this case, the court had to decide if administering a narco-analysis test to the defendant would violate Article 20(3) of the Indian Constitution.

Ratio: According to the court, it will depend on the type of question that is posed to the accused. Whether the accused individual made a remark or provided any information, it was either exculpatory or incriminating, and only incriminating statements are covered under Article 20(3) of the Constitution. Therefore, it is too soon to speculate about the type of statement or information the accused provided during the narcotics analysis test. According to the law, a police officer may gather evidence. Collecting evidence also includes administering the Narco Analysis test to the accused.

Function: The results of the narco-analysis test revealed that Selvi Murugeshan and her spouse were involved.

Held: The Supreme Court established the rule that no narco-analysis test can be performed on an accused individual without first obtaining that person’s agreement. The Court additionally held that this test should be carried out with an expert present.

Nupur Talwar v/s Cbi & Anr 2012

Facts: On May 16, 2008, the body of 14-year-old Arushi Talwar was discovered in her house. This crime is famously known as the Aarushi Talwar-Hemraj Double Murder Case. Arushi’s parents filed the report at the police station. Aarushi Talwar’s body was discovered in her bedroom. Hemraj, a domestic helper in the Talwars’ home, was singled out for suspicion in the initial information report by Dr. Rajesh Talwar, her father. On May 17, 2008, Hemraj’s body was found on the terrace of the same home, i.e. the home where Aarushi’s murder is also thought to have taken place. But after two days, Hemraj’s body was also discovered on the terrace of Arushi’s home.

First hand Investigations conducted by the police revealed the following points:

The pillow and bed sheet of Aarushi had no signs of Hemraj’s blood on them. There is no proof that Hemraj was murdered in Aarushi’s room.

Dragging marks on stairs only suggest that a murder occurred somewhere, not on the terrace.

Only Aarushi’s blood was discovered on Dr. Rajesh Talwar’s clothing; Hemraj’s blood had vanished.

The CBI seized the clothes Dr. Nupur Talwar was wearing in the photo Aarushi took the night of the incident, but no blood was discovered during the forensic examination.

Weapons of murder were not found right away after the crime. Experts were unable to detect any blood stains or victim DNA on the golf stick, one of the murder weapons, which had a sharp edge, to immediately link it to the crime.

The scotch bottle’s finger prints have no supporting proof (which were found along with blood stains of both the victims on the bottle).

The colony’s guards are on the move at night and do not enter the building at the entrance. As a result, their claims about the movement of people could not be accurate.

Although doctors who conducted the post-mortem have stated that the cut was made by a person with surgical training using a small surgical instrument, a board of experts assembled during an earlier investigation team has given an opinion that the possibility of the neck being cut by khukri cannot be ruled out.

The existence of Hemraj’s mobile in Punjab after his murder cannot be explained by any evidence.

Since the crime was committed in a closed apartment, there are no eye witnesses.

Function of the Tests: The aforementioned information prompted questions about whether Dr. Rajesh and Nupur Talwar were responsible for the murders. Police detained Arushi’s parents and told them to submit to forensic examinations. They underwent a narco-analysis test, a polygraph test, and a brain mapping exam in this instance. The court was told that the results of these tests could not be used as evidence in a legal proceeding.

In the Forensic Science Laboratory in Gandhinagar, Gujarat, between February 15 and February 20, 2010, the CBI administered narco-analysis tests to Nupur and Rajesh Talwar. The inquiries, however, came up empty.

Held: Despite administering a narco-test to the Talwar couple, no tangible evidence could be gathered that would aid in further case investigation. Rajesh Talwar and Nupur Talwar were put to the test to see if they knew anything about the case, however neither of them had any additional information on the teen girl’s murder.

 Smt. Selvi v State of Karnataka

Whether they require a voluntary response or not, the results of polygraph and other lie-detection tests are testimonial because they only provide inductive proof of the defendant’s epistemic state. They merely serve as inductive proof of the defendant’s epistemic condition. They are evidence that tries to tell us either: (1) whether or not we can depend on the claims the defendant has made and for which he has claimed authority, or (2) what claims the defendant would make and invite reliance on if he were to testify truthfully.

Therefore, a polygraph exam cannot be used as evidence. But in accordance with the Indian Evidence Act of 1872’s Sections 45 and 45A. This states that any expert witness needed for the case may submit their opinion to the court. Things where the judge lacks expertise include foreign legislation, science, art, the identity of handwriting, and finger impressions. After then, it will be useful to take the matter along by getting the expert’s opinion. The polygraphy test is not admissible as evidence, but the court may accept it as an expert opinion in accordance with Section 45A of the Evidence Act. Additionally, the polygraph test might aid police officers in advancing their investigation.


The use of forensic science in the administration of criminal justice is urgently needed. In criminal cases, the inclusion of scientific or forensic evidence not only helps to identify the truly guilty, but also guards against incorrect conviction of the innocent. A person is presumed innocent until and unless they are proven guilty under Indian law, and an innocent person cannot be found guilty even if 100 offenders are handed over.

With the aforementioned goal in mind, submitting a person to narcoanalysis without his agreement will unquestionably impair his personal freedoms and is a clear violation of the idea of a right-based society.

Because the majority of judges and attorneys lack technical training, the use of scientific evidence in a forensic environment has proven to be challenging for both. The issue of deciding between conflicting scientific explanations rather than a lack of knowledge of the underlying science is what causes courts the most trouble when dealing with scientific data. Law is a living process that evolves in line with societal, scientific, ethical, and other changes. As long as they do not violate fundamental legal principles and are beneficial to society, legal changes and advancements should be incorporated into the legal system. Because India’s commitment to individual freedoms and a fair criminal justice system are at issue, the Central government must take a firm stance on narcoanalysis.

Author: Jasleen Sabherwal

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