Polygraph test of accused Sanjoy Roy, RG Kar's ex-principal Sandip Ghosh and 5 others begins

Lie detection tests began on Saturday for the main accused and six others involved in the alleged rape and murder of a trainee doctor at the state-run RG Kar Medical College and Hospital. The tests will include Sanjay Roy, the primary suspect, who will undergo a polygraph examination in the prison where he is currently incarcerated.

The remaining six individuals, which include former principal Sandip Ghosh, four doctors on duty the night of the incident, and a civil volunteer, will face their tests at the Central Forensic Science Laboratory (CFSL) office in Kolkata. A specialised team from CFSL in Delhi has travelled to the city to oversee the testing procedures.

What is a polygraph test?

A polygraph test, commonly called a lie detector test, measures an individual's physiological responses while responding to questions. According to the American Psychological Association, this test seeks to determine whether a person committed a crime, although it does not measure honesty directly. Instead, the assessment relies on the analysis performed by the polygraph operator.

The polygraph machine records physiological indicators, including heart rate, blood pressure, respiratory changes, and perspiration levels during questioning. Sensitive instruments such as cardio-cuffs or electrodes are employed to monitor these responses, with a numerical value assigned to analyse whether the individual is truthful, deceptive, or uncertain.

How will the lie-detector test help the CBI?

In Roy's case, the polygraph test results could clarify inconsistencies in his statements and alibis. Investigators may identify indications of deceit by evaluating physiological responses that deviate from baseline levels during questioning.

The case, which has drawn significant public attention and protests, was marked by troubling allegations from the Central Bureau of Investigation (CBI).

In a statement to the Supreme Court on Thursday, the CBI claimed that local police attempted to cover up the incident, leading to alterations of the crime scene before the federal agency could assume control of the investigation.

The body of the trainee doctor, who suffered severe injuries, was discovered in a seminar hall of the hospital on August 9. Following the discovery, Sanjay Roy was arrested the next day. Under increasing pressure, the Calcutta High Court ordered the transfer of the investigation from Kolkata Police to the CBI on August 13, prompting the agency to initiate its inquiry a day later.