India, June 28 -- The Kolkata Police on Saturday arrested the security guard of South Calcutta Law College in connection with the gangrape of a first-year law student on campus, marking the fourth arrest in the case.

The guard, identified as 55-year-old Pinaki Banerjee, was taken into custody after three others - including the prime accused, a Trinamool Congress leader and former student - were arrested.

"The security guard was arrested this morning after we found that his replies were incoherent. His presence at the college has been captured in the CCTV installed in the college," news agency PTI quoted Kolkata Police as saying.

Police said the guard failed in his duties during the alleged gangrape incident that took place on the eveni...