In explosive testimony before the special Central Bureau of Investigation court here on Wednesday, Sandeep Tamgadge, chief investigating officer in the 2006 Tulsiram Prajapati fake encounter case, has said that Bharatiya Janata Party president Amit Shah and IPS officers D.G. Vanzara, Dinesh M.N. and Rajkumar Pandiyan were the “principal conspirators” in the controversial killing.