Police dogs are in widespread use across the United States. K-9 units are operated on the federal, state, county, and local level and are utilized for a wide variety of duties, similar to those of other nations. Their duties generally include drug, bomb, and weapon detection and cadaver searches. The most common police dogs used for everyday duties are German Shepherds, though other breeds may be used to perform specific tasks.
On the federal level, police dogs are rarely seen by the general public, though they may be viewed in some airports assisting Transportation Security Administration officials search for explosives and weapons or by Customs and Border Protection searching for concealed narcotics and people. Some dogs may also be used by tactical components of such agencies as the Bureau of Alcohol, Tobacco, Firearms, and Explosives, the Federal Bureau of Investigation, and the United States Marshals Service.
Most police agencies in the United States – whether state, county, or local – use K-9s as a means of law enforcement. Often, even the smallest of departments operates a K-9 team of at least one dog, while the officers of more metropolitan cities can be more used to working with dozens. In the former case, police dogs usually serve all purposes deemed necessary, most commonly suspect apprehension and narcotics detection, and teams are often on call; in the latter case, however, individual dogs usually serve individual purposes in which each particular animal is specialized, and teams usually serve scheduled shifts. In both cases, police dogs are almost always cared for by their specific handlers. K-9s are not often seen by the public, though specialized police vehicles used for carrying dogs may be seen from time to time.
Police dogs also play a major role in American penal systems. Many jails and prisons will use special dog teams as a means of intervening in large-scale fights or riots by inmates. Also, many penal systems will employ dogs – usually bloodhounds – in searching for escaped prisoners.