"CID" is "Crime Investigation Department". It was a popular term in India which kind of loosely translated to "James Bond" and stuff. I do not even know if such a department actually, ever existed in the Police Forces. It was probably a creation of movie scriptwriters. There have been some popular films in the 60's and 70's which were amalgamated take offs on the Bond movies and British pulp fiction like The Saint etc., The detective hero usually belonged to the "C.I.D.". That's probably where the term came from. The detectives - the CID's - always wore Ray Ban kind of dark glasses and a hat. Over the years, the term has slowly almost completely faded from the public vocabulary.