The CBI has sought to know the locations of CCTV cameras in various wards of RG Kar Medical College and Hospital after it emerged that Sanjoy Roy, the main accused in the rape and murder, visited the Emergency Building multiple times on August 7 and 8.

A 31-year-old postgraduate trainee doctor was found dead inside the seminar room on the third floor of the Emergency Building on the morning of August 9. Later, it emerged that she had been raped and murdered.

The seminar room is part of the chest medicine department.

The central investigating agency, which is probing the rape and murder, has found that Roy used to frequent the Emergency Building and had access to all floors.

On the night of August 8, he allegedly went to a spot behind the building around 11pm for a drink. Around 2.45am on August 9, he went to a spot near the trauma care unit of the hospital, CBI sources said.

"Roy was allegedly involved in a scuffle with a doctor some three months before and had screamed at a lady doctor recently. He later apologised," a CBI officer said. "It appears Roy moved in and out of the wards freely." Kolkata Police arrested Roy on August 10 and handed him to the CBI after Calcutta High Court took the probe away from the city cops and assigned it to the central agency.

CBI sources said that while the sleuths were looking for footage of CCTV cameras in the wards of the chest medicine and other departments on the days before the crime, the hospital authorities told them that the cameras did not cover every corner of all wards.

The issue of CCTV footage came up during the last hearing at the Supreme Court on September 9 when solicitor general Tushar Mehta said four video clips, totalling 27 minutes, had been handed to the CBI.

On Friday, the CBI brought the parents of the junior doctor to RG Kar and took them Sanjay Roy to the chest medicine department on the third floor of the Emergency Building.

They were asked to identify the spots where they were made to wait for hours before being allowed to step into the seminar room and see their daughter s body on August 9.

The CBI team also wanted to know what they saw while waiting to enter the seminar room. The officers identified the spot where the parents were made to stand outside the seminar room just before they were allowed to enter.

Around 7.30pm, the parents were driven back home.

Earlier in the day, a team of CBI officers reached the Platinum Jubilee Building of RG Kar and met senior officials of the administration. Agency sources said they were trying to find out about those who were present in the seminar hall on the morning of August 9, how many of those present were connected to RG Kar and the number of police personnel who were there.

Narco test Since a polygraph test on accused Roy turned out to be inconclusive, according to CBI sources, the agency on Friday produced him in the Sealdah court for permission to conduct a narco test on him.

Roy refused to undertake the test and the court turned down the appeal.

Senior officers said in a narco test, the accused is injected with drugs such as sodium pentothal to induce a hypnotic state. The idea is that the accused will speak the truth in such a state.

In a polygraph test, physiological responses like blood pressure and pulse are checked while the accused answers questions.