In the case of rape and murder of a female doctor at Kolkata's RG Kar Medical College, a polygraph test of a total of seven people including former principal Sandip Ghosh is being conducted on Saturday. Apart from Sandip Ghosh, rape accused Sanjay Roy and four other doctors of the medical college are also being subjected to polygraph test. Also, a civil volunteer of the hospital is also being subjected to polygraph test.Role of former principal of RG Kar Medical College Sandip Ghosh is suspicious in the case of rape and murder of a female doctor. Sandip Ghosh is being continuously questioned by the CBI for more than a week. According to media reports, there is contradiction in the statements of Sandip Ghosh during the interrogation. Also, the Supreme Court had raised serious questions about the role of Sandip Ghosh during its hearing. This is the reason why Sandip Ghosh is on the radar of CBI investigation. CBI had filed an application in the court seeking permission to conduct polygraph test of Sandip Ghosh, accused Sanjay Roy and four other doctors and a civil volunteer, which was approved by the court.