The lie detection test on Sanjay Roy, the main accused in the alleged rape and murder of an RG Kar Medical College trainee doctor, is underway at Kolkata's Presidency Jail where he is lodged, officials said on Sunday.
Two more individuals will undergo the test at the CBI office in Kolkata during the day, they said.
Four persons including former principal Sandip Ghosh underwent the polygraph test on Saturday, the officials said.
The CBI has sought permission from court to put seven persons including Roy and former principal of the medical college Sandip Ghosh through lie detector test.
The test cannot be used as evidence during the trial but findings give the agency a direction for the further probe.
A team of polygraph specialists flown to Kolkata from the Central Forensic Science Laboratory in Delhi is conducting the tests, they said.
Roy was arrested by the Kolkata Police on August 10, a day after the body of the 31-year-old medic was found in the Seminar hall of the medical college.
CCTV footage and a Bluetooth device found near the medic's body resulted in the arrest of Roy, who was allegedly seen entering the seminar hall of the college where the body was found at around 4 am.
Roy (33) was working with the Kolkata police as a civic volunteer since 2019.
The accused, who is a trained boxer, allegedly got close to a few senior police officers over the years, following which he was moved to the Kolkata Police Welfare Board and posted at the police outpost at the RG Kar Medical College and Hospital.
He has denied the allegations against him.
The CBI earlier told the Supreme Court that the crime scene was altered by the time it took over the probe which suggests there was an attempt by the local police to cover up the rape and killing of the post-graduate medic.
The medic's body with severe injury marks was found inside the seminar hall of the hospital's chest department in the morning of August 9.
The incident has sparked widespread protests.
The Calcutta high court on August 13 ordered the transfer of the probe from the Kolkata Police to the CBI, which started its investigation on August 14.
