Presuming that police in a state has already registered a case, investigation of such police case can be taken over by CBI mainly in one of the following three ways:
(1) State Government gives its consent for its transfer to CBI. This can happen, generally, when the State Government itself makes a request to the Centre in this regard (generally, when the case is complicated or sensitive or has wider ramifications beyond the state) and the Centre accordingly agrees and issues a notification for such transfer. Or, it may so happen that the Centre requests the State Government to give consent for the transfer of the case to the CBI (generally, when the case has wider inter-state or international ramifications), whereupon the State gives its consent and then the Centre issues a notification for transfer of the case to CBI. But, in both these situations, consent of the State Government is of essence.
(2) Supreme Court directs transfer of the case to the CBI.
(3) The concerned High Court, having jurisdiction, directs transfer of the case to the CBI.
In the second and third scenario, consent of the State Government is not necessary.
