Law enforcement in the United States operates primarily through governmental police agencies. There are 17,985 police agencies in the United States which include municipal police departments, county sheriff's offices, state police and highway patrols, and federal law enforcement agencies. The law enforcement purposes of these agencies are the investigation of suspected criminal activity, referral of the results of investigations to state or federal prosecutors, and the temporary detention of suspected criminals pending judicial action. Law enforcement agencies are also commonly charged with the responsibilities of deterring criminal activity and preventing the successful commission of crimes in progress. Other duties may include the service and enforcement of warrants, writs, and other orders of the courts.
In the United States, police are considered an emergency service involved in providing first response to emergencies and other threats to public safety; the protection of certain public facilities and infrastructure, such as private property; the maintenance of public order; the protection of public officials; and the operation of some detention facilities (usually at the local level).
, more than 600,000 sworn law enforcement officers are serving in the United States. About 137,000 of those officers work for federal law enforcement agencies.
Types of law enforcement agencies Policing in the United States is conducted by "around 18,000 federal, state and local law enforcement agencies, all with their own rules". Every state has its own nomenclature for agencies, and their powers, responsibilities and funding vary from state to state. 2008 census data from the Department of Justice's Bureau of Justice Statistics (BJS) revealed that this constitutes:
73 federal agencies 50 primary state law enforcement agencies 1,733 special jurisdiction agencies 3,063 sheriff's offices 12,501 city, county, tribal, and regional police departments
Federal
At the federal level, there exists both federal agents, which possess full federal authority as given to them under United States Code (U.S.C.), and federal law enforcement agencies, who are authorized to enforce various laws at the federal level. Both police and law enforcement agencies operate at the highest level and are endowed with police roles; each may maintain a small component of the other (for example, the FBI Police). The agencies have jurisdiction in all states, U.S. territories, and U.S. possessions for enforcement of federal law. Most federal agencies are limited by the U.S. Code to investigating only matters that are explicitly within the power of the federal government. However, federal investigative powers have become very broad in practice, especially since the passage of the Patriot Act. There are also federal law enforcement agencies, such as the National Park Service Law Enforcement Rangers, that are granted state arrest authority off primary federal jurisdiction.
The Department of Justice (DOJ) is responsible for most law enforcement duties at the federal level. It includes the Federal Bureau of Investigation (FBI), the Drug Enforcement Administration (DEA), the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF), the United States Marshals Service, and the Federal Bureau of Prisons (BOP).
The Department of Homeland Security (DHS) is another branch with numerous federal law enforcement agencies reporting to it. The United States Border Patrol (USBP), U.S. Immigration and Customs Enforcement (ICE), United States Secret Service (USSS), United States Coast Guard (USCG), and the Transportation Security Administration (TSA) are some of the agencies that report to the DHS. The Army National Guard and Air National Guard in particular is also a Military Police Corps (United States Army), Master-at-arms (United States Navy), United States Air Force Security Forces, and United States Marine Corps Military Police of the United States Armed Forces and is assigned to the United States Department of Defense in the event of war.
At a crime or disaster scene affecting large numbers of people, multiple jurisdictions, or broad geographic areas, many police agencies may be involved by mutual aid agreements. For example, the United States Federal Protective Service responded to the Hurricane Katrina natural disaster. The command in such situations remains a complex and flexible issue.
In accordance with the federal structure of the United States government, the national (federal) government is not authorized to execute general police powers by the Constitution of the United States. The power to have a police force is given to each of the United States' 50 federated states. The Constitution gives the federal government the power to deal with foreign affairs and interstate affairs (affairs between the states). For police, this means that if a non-federal crime is committed in a U.S. state and the fugitive does not flee the state, the federal government has no jurisdiction. However, once the fugitive crosses a state line, he violates the federal law of interstate flight and is subject to federal jurisdiction, at which time federal law enforcement agencies may become involved.
Security-oriented agencies Certain federal law enforcement agencies operate primarily as security forces for their parent agency's properties and buildings by providing access control, emergency response, site security, and protection for sensitive facilities. These law enforcement officers have a more limited scope of responsibility and generally have a jurisdiction limited to federal property and its surrounding area.
Examples United States Federal Protective Service United States Secret Service Uniformed Division United States Capitol Police Supreme Court of the United States Police Department FBI Police United States Treasury Police United States Mint Police Federal Reserve Police Central Intelligence Agency Security Protective Officers National Security Agency Police NASA Office of Protective Services (NASA OPS)
Gendarmerie
The American equivalent of Gendarmerie (a military force tasked with law enforcement) is the United States Coast Guard. The Coast Guard is maritime law enforcement agency part of the United States Armed Forces and is exempt from the Posse Comitatus Act (a U.S. law banning the Armed Forces from engaging in law enforcement operations). Additionally when National Guard forces are under state control they are exempt from the Posse Comitatus Act.
State
Most states operate statewide law enforcement agencies that provide law enforcement duties, including investigations and state patrols. They may be called state police or highway patrol (state troopers), and are normally part of the state Department of public safety. In addition, the Attorney General's office of each state has its own state bureau of investigation, such as in California with the California Department of Justice. The Texas Ranger Division fulfills this role in Texas, although they were founded in the period before Texas became a state.
Various departments of state governments may have their own enforcement divisions, such as capitol police, campus police, water police, environmental (fish and game/wildlife) conservation officers, or game wardens (with full police powers and statewide jurisdiction). For example, in Colorado, the Department of Revenue has its own investigative branch.
County Also known as parishes and boroughs, county law enforcement is provided by sheriffs' departments or offices, constables and county police.
County police
County police tend to exist only in metropolitan counties and have countywide jurisdiction. For places that have both county police and county sheriff, responsibilities are given to each: the county police are in charge of typical police duties such as patrol and investigations, whereas the sheriffs' department in this situation takes care of serving papers and providing security to the courts. County police tend to fall into three broad categories, full service, limited service, and restrictive service. Full service provides full police services to the entire county. Limited service provides to the unincorporated and special districts. Restricted service provide security to the county-owned parts of the county.
Sheriffs' offices
Sheriffs are law enforcement officers who have many different responsibilities and functions from state to state. Sheriffs are elected officials who are appointed or hired in. Sheriffs are responsible for all three parts of the criminal justice system. They uphold the county jail, ensure safety within the courts, and may have jurisdiction to enforce laws in the entire county. They have more responsibilities such as transporting prisoners, running crime labs, and collecting taxes.
In Texas, the sheriff's office is normally the agency responsible for handling mental health calls. If the situation is dangerous, a sheriff's deputy has the power to take a person to a hospital on a mental health commitment immediately. However, if the situation is not actively dangerous, a warrant must be sought. With the rise in mental health units across the state, the Texas CIT Association was formed.
Commonwealth of Virginia
The Commonwealth of Virginia does not have overlapping county and city jurisdictions, whereas in most other states, municipalities generally fall within (and share jurisdiction and many other governmental responsibilities with) one (or more) county(ies). In Virginia, governmental power flows down from the state (or in Virginia's case, commonwealth) directly to either a county or an independent city. Thus, policing in Virginia is more streamlined: the county sheriff's office/department or county police department does not overlap with an independent city police department. Unincorporated townships remain part of their parent county, but incorporated townships may have town police departments to augment their county law enforcement. Town police departments are often small and may deploy a combination of paid and unpaid, full and part-time law enforcement officers, including auxiliary officers who typically serve as part-time, unpaid volunteers. If present, independent city sheriff's offices usually follow the restrictive model shown above for sheriff's departments, with limited law enforcement authority including warrant service, jail bailiff, etc. Mutual assistance compacts may exist where neighboring law enforcement agencies will assist each other, however, in addition to state (commonwealth) law enforcement resources. Like most states, Virginia also has campus police officers. Under Virginia State Code 23.1-809 and 23.1-810, public and private colleges and universities can maintain their own armed police force and employ sworn campus police officers. These sworn officers have the same authority as local police and are required to complete police academy training mandated by the Virginia Department of Criminal Justice Services. Virginia campus police officers have jurisdiction on and immediately around the campus, but police departments may petition to the local circuit court for concurrent jurisdiction with the local police.
Municipal
Municipal police range from one-officer agencies (sometimes still called "town marshals") to the 40,000 person-strong New York City Police Department, which has its own counterterrorism division. Most city agencies take the form (Municipality Name) Police Department. Most municipalities have their own police departments.