The CBI on Friday sought permission to conduct a narco test on Sandip Ghosh, the former principal of RG Kar Medical College and Hospital, and a polygraph test on Abhijit Mondal, the suspended officer-in-charge of Tala police station.

In an appeal before the Sealdah court, where the two were produced during the day, the CBI placed separate appeals.

“There is something between the two which is yet to surface. We want to conduct a narco test on Ghosh and a polygraph test on Abhijit to understand the greater conspiracy that was in place,” the CBI lawyer told the court.

Sources in the CBI said the probe team wants to conduct the narco test on Sandip at an institute in Gujarat.

The judge hearing the CBI appeal asked whether the agency found any credible lead to suggest that both Sandip and Abhijit were involved in the rape and murder of the junior doctor at the RG Kar.

The two were arrested on September 14 for their alleged involvement in the rape and murder case.

Sandip was “shown arrest” because he was in CBI custody in a separate case relating to alleged financial irregularities at RG Kar. Abhijit was arrested after almost seven hours of interrogation at the CBI’s CGO Complex office in Salt Lake.

The CBI lawyer told the court that the two accused were known to each other and remained co-conspirators in the rape and murder case. Abhijit’s statements did not match with his colleagues in connection with the probe, the CBI lawyer said.

After hearing both sides, the judge fixed the next hearing for the narco and polygraph appeal on September 23.

Earlier, a CBI appeal to conduct a narco analysis test on Sanjay Roy, prime accused in the rape and murder case, was turned down by the Sealdah court after he refused to agree to undergo the test.

Senior police officers said in narco analysis, the accused is injected with drugs like sodium pentothal to induce a hypnotic state. The idea is that the accused will speak the truth in the sedated state.

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