Delhi Fridge murder: Aaftab Poonawala to undergo polygraph test- how does it work 

A court on Tuesday gave Delhi Police permission to conduct a polygraph test on Aaftab Amin Poonawala. who allegedly killed and dismembered the body of his live-in partner Shraddha Walkar, police sources said on Tuesday.

Delhi Police had moved it application in court on Monday.

"Yes. We have received permission from the Delhi Court to conduct a polygraph test on Poonawala," a police official told PTI.

A polygraph test is a non-invasive technique in which no medicine is used. The subject is attached to a machine and questions are asked to him/her about the matter related to any case or incident. The variation in the graph when the subject answers the questions are mapped to draw a conclusion.

According to the American Psychological Association (APA), polygraph tests measure a person's "heart rate/blood pressure, respiration, and skin conductivity". The purpose of the test is usually to prove whether or not a person committed a crime.