The United States maintains a complex network of law enforcement agencies at the local, state and federal levels. These agencies have varying degrees of specialty and work closely with one another and the courts. Functions performed by the levels of police agencies in the United States run a gamut, from preventing the importation of illegal drugs to ensuring the safety of students at universities. The role of a police agency depends upon its location and jurisdiction. many as 23,000 local and state police agencies exist in the United States as of 2011, depending upon the method of counting them. Types of police agencies under state jurisdiction include local township or city police forces, state police, countrywide sheriff’s offices, state highway patrols and constables. The structure and levels of state police agencies differs in each state. Hawaii, for instance, maintains no state police force per Se, but rather a Department of Public Safety. In most states, sheriffs serve as elected officials and act as political liaisons between state governments and police agencies. Various agencies perform specialized police functions at state level. Fish and game wardens, for instance, enforce hunting, fishing, boating laws. According to O’Connor, 35 U.S. states invest independent agencies such as the Department of Criminal Investigations, Department of Motor Vehicles and Alcohol Beverage Control with special, limited powers of law enforcement and investigation. These agencies enforce laws within their jurisdiction, often with the cooperation of other police agencies. Other special divisions of police agencies include K-9 units, which work with police dogs, HAZMAT units, which handle hazardous materials and SWAT, or special tactical units.