The CBI on Wednesday began the process of conducting a polygraph test on Kolkata Police ASI Anup Dutta to decipher his alleged links with Sanjay Roy, arrested in the rape and murder case of a trainee doctor at RG Kar Medical College and Hospital, officials said.

The Central Bureau of Investigation (CBI) had taken permission from a Kolkata court to conduct the polygraph test on Assistant Sub-Inspector Dutta, who was earlier questioned by the agency in the case.

Dutta will be the eighth person to undergo a polygraph test in this case.

According to the officials, Dutta, posted in the Kolkata Police Welfare Committee, had allegedly extended a number of favours to Roy, a traffic police volunteer.

The CBI is trying to find out if Roy informed Dutta about the crime he allegedly committed and whether he sought any favours for covering up the crime, the officials said.

The information revealed during the polygraph test may not be used as evidence during the trial but the agency may gather corroborative evidence which could be used in court, they said.

A polygraph test can help in assessing inaccuracies in the statements of suspects and witnesses. By monitoring their psychological responses, heart rate, breathing pattern, sweating and blood pressure, investigators can determine if there are discrepancies in their responses.

The trainee doctor was allegedly raped and murdered in the seminar hall of RG Kar Medical College and Hospital when she had gone to rest during her graveyard shift in the early hours of August 9.

Her body with severe injury marks was found inside the hall by a doctor who was on rounds.

Roy was arrested the next day based on CCTV footage in which he was seen entering the seminar hall at 4.03 am on the day of the incident.

He was put through extensive interrogation when "recent injuries" on his left cheek, abrasion on the left hand and the back of his left thigh, among others, showing signs of struggle were recorded by police.

His biological samples like urethral swab and smear, semen, hair, nail clippings and nail scraping were collected during the medico-legal examination.

On August 13, the Calcutta High Court ordered the transfer of the probe from the Kolkata Police to the CBI, which took over the case on August 14.

After taking over the case, the CBI subjected Roy, former principal of the medical college Sandip Ghosh, four doctors who were on duty with the victim, and a civic volunteer to polygraph tests to get further leads about the crime.

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