Detective

A detective is an investigators, usually a member of an enforcement agency. They often collect information to unravel crimes by lecture witnesses and informants and also by collecting physical evidence or searching records in databases. This leads them to arrest criminals and enables them to be convicted in court. A detective may go for the police or privately.

The detective branch in most large police agencies is organized into several squads or departments, each of which focuses on investigation into a specific sort of crime or a specific type of operation which can include are homicide and robbery and burglary and auto theft and organized crimes and missing persons also include juvenile crime, fraud, narcotics, vice, criminal intelligence, among others.

In police departments of the US, a daily detective typically holds the rank of "Detective". The rank structure of the officers who supervise them (who may or might not be detectives themselves) varies considerably by department. In Commonwealth police forces, detectives have equivalent ranks to uniformed officers but with the word "Detective" prepended thereto 

Before the 19th century, there were few municipal police departments, though the primary had been created in Paris in 1667. As police activities moved from appointees helped by volunteers to professionals, the thought of dedicated detectives didn't immediately arise. The first PI agency was founded by Eugène François Vidocq in Paris within the early 1820s, who had also headed a police agency additionally to being a criminal himself. Detective activities were pioneered in England by the Street Runners and later the Metropolitan Police Service in London. The first detective unit in the US was formed in 1846 in Boston.