Detective Chief Inspector. Chief Inspector (Ch Insp) is a rank used in police forces which follow the British model. In countries outside Britain, it is sometimes referred to as Chief Inspector of Police (CIP).
Detective Chief Inspector (DCI) is usually the minimum rank held by a Senior Investigating Officer (SIO), who heads major investigations (into murder, for example), and a pool of these officers usually works out of force headquarters or major police stations. The senior Criminal Investigation Department (CID) officer in each Basic Command Unit (BCU) usually also holds this rank.
The DCI is interrogating a suspect.