Police detective

A detective is an investigator, usually a member of a law enforcement agency. Some are private persons, and may be known as private investigators, as "The Eye That Never Sleeps", the motto of the Pinkerton Detective Agency or shortened to simply "private eyes".

Informally, and primarily in fiction, a detective is any licensed or unlicensed person who solves crimes, including historical crimes, by examining and evaluating clues and personal records in order to uncover the identity and/or whereabouts of the criminal.

In some police departments, a detective position is achieved by passing a written test after a person completes the requirements for being a police officer. In many other police systems, detectives are college graduates who join directly from civilian life without first serving as uniformed officers. Some people argue that detectives do a completely different job and therefore require completely different training, qualifications, qualities and abilities than uniformed officers. The opposing argument is that without previous service as a uniformed patrol officer, a detective cannot have a great enough command of standard police procedures and problems and will find it difficult to work with uniformed colleagues.

The detective branch in most large police agencies is organized into several squads or departments, each of which specializes in investigation into a particular type of crime or a particular type of undercover operation, which may include: homicide; robbery; burglary; auto theft; organized crimes; missing persons; juvenile crime; fraud; narcotics; vice; criminal intelligence; aggravated assault/battery; sexual assault; computer crime; domestic violence; surveillance; and arson, among others.

...
Wikipedia