What is a detective and why are they called "gumshoes"? A detective is an investigator within a law enforcement agency. "Gumshoe" is an old term used because detective work typically requires a great deal of walking or "footwork", leading to the slang terms "flatfoot" and "gumshoe". The term "gumshoe" refers to an inexpensive shoe with gum rubber soles that were believed to be quieter due to their softness, enabling detectives to operate in stealth.
      Promotion: In most police departments, the person selected for promotion to a detective position must first serve as a uniformed officer for a specified period of time. It can an appointed position and not require passing a written test; however, this may vary from one agency to another. Some police departments require detectives to return to patrol duties for a minimum period of time so the detective isn't in continuous service in the detective position. The reason for this is that some departments believe the most essential police work is done on patrol which helps the detective refresh certain skills they may not have had time to focus on when they're away from patrol. Rotating officers also promotes cross-training in a wider variety of skills, producing both better detectives and uniformed officers.
      The detective branch in most larger police agencies is organized into several squads or units, each of which specializes in investigating a particular type of crime. Such units include homicide, robbery, motor vehicle theft, organized crime, burglary, narcotics, criminal intelligence, sex crimes, crimes against children, surveillance, and arson. These units can be further subdivided in smaller categories as needed.
      Investigations: Detectives have a wide variety of techniques available to conduct investigations. Most cases are solved by the interrogation of suspects and the interviewing of witnesses. Detectives may also rely on informants with whom they've built trust and respect. Informants can sometimes talk to people and get information when the people with the information won't talk to anyone they suspect is a "cop". Evidence collection and preservation help in identifying potential suspects.
      Once a detective has a list of suspects, the next step is to find, collect, and preserve evidence that will stand up in a court. The best way is to obtain a confession from the suspect; usually, this is done by developing rapport and at times by seeking information in exchange for potential perks available through the District Attorney's Office, such as entering a plea bargain for a lesser sentence in exchange for usable information. In the United States, suspects may invoke their Fifth Amendment rights and refuse to answer any questions until they consult with an attorney.
      What other sources can a detective use? Detectives may use public and private records to provide background information on a suspect. They can search through files of fingerprint records. In the United States, the FBI maintains records of people who have committed felonies and some misdemeanors, all persons who have applied for a Federal security clearance, and all persons who have served in the U.S. armed forces. They may also search through records of criminal arrests and convictions, photographs of people who've previously been arrested, and motor vehicle records. With a warrant, detectives can also search through credit card records and bank statements, hotel registration information, credit reports, answering machine messages, and phone conversations. In order to obtain these warrants, the detective must be able to establish probable cause.