The FBI is the principal investigative arm of the United States Department of Justice. It is primarily charged with gathering and reporting facts, locating witnesses, and compiling evidence in cases involving Federal jurisdiction. It also provides law enforcement leadership and assistance to State and international law enforcement agencies. The Federal Bureau of Investigation was established in 1908 by the Attorney General, who directed that Department of Justice investigations be handled by its own staff. The Bureau is charged with investigating all violations of Federal law except those that have been assigned by legislative enactment or otherwise to another Federal agency. Its jurisdiction includes a wide range of responsibilities in the national security, criminal, and civil fields. Priority has been assigned to areas such as counterterrorism, counterintelligence, cyber-crimes, internationally and nationally organized crime/drug matters, and financial crimes. The FBI also offers cooperative services to local, State, and international law enforcement agencies. These services include fingerprint identification, laboratory examination, police training, the Law Enforcement Online communication and information service for use by the law enforcement community, the National Crime Information Center, and the National Center for the Analysis of Violent Crime.

The Uniform Crime Reporting (UCR) Program was conceived in 1929 by the International Association of Chiefs of Police to meet a need for reliable, uniform crime statistics for the nation. In 1930, the FBI was tasked with collecting, publishing, and archiving those statistics. Today, several annual statistical publications, such as the comprehensive Crime in the United States, are produced from data provided by nearly 17,000 law enforcement agencies across the United States. Other annual publications, such as Hate Crime Statistics and Law Enforcement Officers Killed and Assaulted, address specialized facets of crime.