Arizona v. Fulminante

The Federal Bureau of Investigation (FBI) is a unit of the Department of Justice responsible for investigating federal crimes. Its purview consists of all areas of law not otherwise assigned to federal agencies--for example, the Drug Enforcement Agency (DEA). Though it does not prosecute crimes, it provides assistance to federal, state, and local agencies engaged in prosecution.

In 1908, President Theodore Roosevelt called for the development of a special investigative unit within the Justice Department. The following year, Attorney General George W. Wickersham established the Bureau of Investigation, later named the Federal Bureau of Investigation in 1935. During World War I and afterward, the FBI was involved in a wave of investigations regarding subversive activities. The bureau became more prominent during Prohibition, when it faced prominent gangsters, bootleggers, and other criminals. In 1924, J. Edgar Hoover became FBI director, a position he would hold for 48 years. Under his tenure, the bureau concerned itself with civil rights activities and operations of organized crime. In the years since, the FBI has been involved in a number of investigative areas, including background checks, counterintelligence, and white-collar crime.