The Criminal Investigation Department (CID) is the branch of all Territorial police forces within the British Police and many other Commonwealth police forces, to which plain clothes detectives belong. It is thus distinct from the Uniformed Branch and the Special Branch.
CID officers are required to have had at least two years as a uniformed officer before applying to transfer to the branch and receive further training when they do so. While training they are referred to as a Training Detective Constable (TDC) and after a years training period they become a fully fledged Detective Constable (DC). CID officers are involved in investigation of major crimes such as rape, murder, serious assault, fraud, and any other offences that require complex detection They are responsible for acting upon Criminal investigation received and then building a case, from analysis of the initial incident through to arrest and prosecution of any suspects.
In the United Kingdom, smaller police stations usually have more uniformed officers than CID officers. Usually having five Detective Constables (DC) with a Detective Sergeant (DS) in overall command, but in larger stations usually many DCs DSs and Detective Inspectors will be present with the overall command of the department the responsibility of the Detective Chief Inspector
These ranks are common to most forces.
The Army SIB has regular Sections and one Territorial Army Section made up of civilian CID officers and ex-regulars to assist them in major cases.