Polygraph and Narco Analysis tests: What are they and do they really bust lies?

New Delhi, Nov 23: Aftab Amin Poonawala, the accused in the murder of Shraddha Walkar, underwent a polygraph test on Tuesday and the investigating team will conduct a narco analysis test on him soon.

The cops are hoping to find clues to recover key evidence, including the murder weapon, that could firm up their case against Aftab, who has reportedly confessed to have dismembered her body and dumped it piece by piece for 18 days after strangling her to death on May 18.

A questionnaire has been prepared for the polygraph test so that the sequence of events in the gruesome killing can be ascertained, sources told PTI on Monday.

So, what are polygraph test and narco analysis tests?

Polygraph test, popularly known as lie-detector test, is commonly used by investigating officers to determine whether an individual is telling truth or deceiving them. It is based on the scientific assumption that lying causes stress. Some studies have claimed that when we hide something, the part of the brain that regulates emotion, called the amygdala, lights up.

The person, who undergoes the test, is asked several questions while equipment is attached to his body to monitor the movements of blood pressure, electrodes which are placed on the fingers or palm, and two tubes which are wrapped around the chest and stomach.

"When we lie (i.e., deliberately utter a falsehood with the intention to deceive), our brain arousal level is increased because of a catecholaminic response that is triggered by the Autonomic Nervous System. This system is also responsible for other body changes that can be detected easily by lie detector tests, including voice modulation, which can be detected via "voice stress analyzers"; pupil mydriasis; increase in respiratory and cardiac frequency; and skin conductance changes (electrodermal response)," a study conducted by the National Library of Science said.

It usually measures like blood pressure, changes in the individual breathing or sweating on the palms.

Can an individual cheat?

The polygraph test basically measures physiological responses and the person, out of fear, may say the things that he does not want to say. It means an honest man might be nervous while responding to questions and might give inaccurate responses. "These physiological indexes reflect an emotional perturbation rather than the cognitive act of lying. Therefore, these indexes cannot be used reliably to identify deception if an innocent suspect experiences these physiological changes due to fear," the study points out.

Also, with a little bit of training, experts say you can cheat. "There's no question that you can beat a polygraph test but you really need the training to do it," BBC quoted Don Grubin, who has trained polygraph examiners in the UK, as saying.

One can fool a lie detector by deliberately distorting physiological readings when telling the truth like biting tongue or imagining an embarrassing incident. "Similar problems afflict brain scan lie detectors, which follow the same principle of needing a reliable baseline against which to compare signs of lying," as per a report in Science Focus.

Another study has also pointed out that if you are a habitual liar, your brain is desensitized to lies. So, the authenticity of the tests has always been questioned.

Let us not forget, there are plenty of resources available on internet to pass a lie detector.

What is Narco Analysis?

The test is conducted by injecting sodium pentothal, also called 'truth serum' into a person, thus reducing an individual's self-consciousness. In such a sleep-like state, efforts are made to obtain probative truth about the crime. The dose of the injected substance is decided as per the person's sex, age, health, and physical condition, according to PTI report.

The accused is then interrogated by the investigating agencies in the presence of doctors. The revelations made during this stage are video recorded. Based on his statements, the report prepared by the expert is used in the process of collecting evidence. The procedure is conducted at a government hospital, after a court order permitting the same.

According to Forensic Science Laboratory officials, during the test, first the investigator submits the case with the laboratory and briefs them.

"Then, our psychologist has a session with investigating officer (IO). The experts interact with the suspect where he is apprised about the test as his consent is mandatory. Only when the psychologists are satisfied that the suspect has understood, he is medically examined and the process begins," an official said, adding the photography team is also sent from the laboratory.

Are Lie Detector and Narco Analysis Test Admissible in Court?

The Supreme Court had earlier said that narco-analysis or polygraph tests on an accused are illegal. However, the court permitted use of such truth-finding techniques in criminal cases on consent.

"We hold that no individual should be forcibly subjected to any of the techniques in question, whether in the context of investigation in criminal cases or otherwise. Doing so would amount to an unwarranted intrusion into personal liberty," The Times of India had quoted a bench comprising chief justice K G Balakrishnan, Justice R V Raveendran and Justice J M Panchal as saying in the case of Selvi vs State of Karnataka.

According to Article 20(3) of the Indian Constitution, no person who is accused of a crime can be compelled to be a witness against himself.

The narco analysis test was most notably used in the 2002 Gujarat riots case, Abdul Karim Telgi fake stamp paper scam, the Nithari killings case in 2007 and the 26/11 Mumbai terror attack case on captured terrorist Ajmal Kasab.

While 26/11 convict Ajmal Kasab and Abu Salem's tests were successful, the results of some high-profile cases like Aarushi Talwar murder case and Abdul Karim Telgi fake stamp paper scam did not establish genuine conclusions.

The courts do not accept statements made under a polygraph or narco test. In fact, whatever the accused says is not admissible in courts unless the statement is made before a magistrate in person.

The court clearly states that the accused must have access to a lawyer and he should be explained about the physical, emotional, and legal implications of the test by police and the lawyer. Yet the results of the tests cannot be considered confessions.

In common man's terms, if the confession during the polygraph test helps in finding a new piece of evidence to the prosecuting agency, then the same can be used against the accused as per Section 27 of the Indian Evidence Act. Suppose, the accused in a murder reveals that he kept the weapon used to kill beneath the mattress of his bedroom and the cops be able to recover it based on this information, then it will be useful for prosecution during the trial before the court.