New Delhi, November 17: A Delhi Court ordering narco test for Aaftab Amin Poonawala in the bone-chilling Shradha Walkar killing case has put the spotlight on use of the specialised examination as an advanced tool for interrogation.

Here is what a narco test means. Also known as truth serum, it has been used for solving crucial cases in the past. Shraddha Walkar Murder Case: Saket Court Approves Narco Test of Accused Aftab Ameen Poonawalla.

The test involves the intravenous administration of a drug (such as sodium pentothal, scopolamine and sodium amytal) that causes the person undergoing it to enter into various stages of anaesthesia. Shraddha Walker Murder Case: Accused Aftab Amin Poonawala's Police Custody Extended For Five More Days.

In the hypnotic stage, the person becomes less inhibited and is more likely to divulge information, which would usually not be revealed in the conscious state.

The investigating agencies use this test after other evidences do not provide a clear picture of the case. According to norms, the consent of the person is also necessary for being subjected to narco test.

The Supreme Court had ruled that narco analysis, brain mapping and polygraph tests cannot be conducted on any person without his or her consent. The apex court had noted in response to petitions questioning the validity of such tests, are illegal and a violation of personal liberty.

However, statements made during narco analysis test are not admissible in the court, except under certain circumstances when the court thinks that the facts and nature of the case permit it.

The term narco-analysis is derived from the Greek word narko (meaning anaesthesia or Torpor) and is used to describe a diagnostic and psychotherapeutic technique that uses psychotropic drugs, particularly barbiturates.

According to experts, during the narco test, the person's inhibitions are lowered by interfering with his or her nervous system at the molecular level. 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.

The person concerned is then interrogated by the investigating agencies in the presence of doctors. The revelations made during this stage are video recorded. 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.

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.

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.

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