Shraddha Walkar murder case: What is the difference between narco and polygraph test?

On November 17, the court approved a narco-analysis test to be conducted on Poonawala to help investigators find the missing weapon and other evidence in the case.

Poonawala today informed the court that he had murdered his girlfriend in the “heat of the moment”. He is accused of allegedly chopping Walkar’s body into multiple pieces and discarding them over the next few months.

Both polygraph and narco routines are Deception Detection Tests (DDTs) carried out in a bid to bring out concealed information.

Also known as the lie detector test, a polygraph test is a non-invasive technique in which no medicine is used. The person on whom the test is conducted is attached to a machine that maps his or her physiological behaviour. The subject is asked questions on matters relating to the case or incident.

According to the American Psychological Association, parameters such as the person’s blood pressure, pulse, respiration, and skin conductivity are measured and recorded. The variation in the graph is noted to draw a conclusion. The test is usually conducted to prove if a person has committed a crime.

The narcoanalysis test is a lengthier process in which the accused is injected with the drug sodium pentothal or sodium thiopental. These are fast-acting, short-duration anaesthetics, which are used in larger doses to sedate patients during surgery. The drugs take the subject to a hypnotic or sedated state. While in this state, they are asked questions as their resolve to lie becomes weak. The police use this method to extract information that the accused may be hiding. The drug used in the narco test is nicknamed ‘truth serum’.

Investigating agencies now resort to polygraph and narco tests as a ‘softer alternative’ to subjecting the suspects to torture or ‘third degree’. However, scientifically all DDTs are not 100 percent accurate. The Supreme Court does not consider them as fool-proof confessions as the suspect is under the influence of a drug and had no choice over the answers they gave out. However, police often use these answers to discover new material or information which can be submitted as evidence.

ALSO READ: Delhi govt think tank office sealed as L-G asks CM to remove Jasmine Shah as DDCD V-C