History: United States Of America, 1900-1930

Crime and law enforcement
Law enforcement in the United States is primarily the responsibility of local police and sheriff's departments, with state police providing broader services. Federal agencies such as the Federal Bureau of Investigation (FBI) and the U.S. Marshals Service have specialized duties. At the federal level and in almost every state, jurisprudence operates on a common law system. State courts conduct most criminal trials; federal courts handle certain designated crimes as well as certain appeals from the state systems.
Among developed nations, the United States has above-average levels of violent crime and particularly high levels of gun violence and homicide. In 2007, there were 5.6 murders per 100,000 persons, three times the rate in neighboring Canada. The U.S. homicide rate, which decreased by 42% between 1991 and 1999, has been roughly steady since. Gun ownership rights are the subject of contentious political debate.