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.
In a ‘narco’ or narcoanalysis test, a drug called sodium pentothal is injected into the body of the accused, which transports them to a hypnotic or sedated state, in which their imagination is neutralised.
In this hypnotic state, the accused is understood as being incapable of lying, and is expected to divulge information that is true.
Sodium pentothal or sodium thiopental:
Sodium pentothal or sodium thiopental is a fast-acting, short duration anaesthetic, which is used in larger doses to sedate patients during surgery.
It belongs to the barbiturate class of drugs that act on the central nervous system as depressants.
Because the drug is believed to weaken the subject’s resolve to lie, it is sometimes referred to as a “truth serum”, and is said to have been used by intelligence operatives during World War II.
Polygraph test:
A polygraph test is based on the assumption that physiological responses that are triggered when a person is lying are different from what they would be otherwise.
A polygraph test does not involved injecting drugs into the body; rather instruments like cardio-cuffs or sensitive electrodes are attached to the suspect, and variables such as blood pressure, pulse rate, respiration, change in sweat gland activity, blood flow, etc., are measured as questions are put to them.
A numerical value is assigned to each response to conclude whether the person is telling the truth, is deceiving, or is uncertain.
In ‘Selvi & Ors vs State of Karnataka & Anr’ (2010), a Supreme Court Bench comprising then Chief Justice of India K G Balakrishnan and Justices R V Raveendran and J M Panchal ruled that no lie detector tests should be administered “except on the basis of consent of the accused”.
