A police dog is a dog that is trained specifically to assist police and similar law-enforcement personnel with their work. They are also known in the United States as police K9s.

The term is also sometimes incorrectly used to refer to any German Shepherd Dog because they were often depicted as police dogs in television and movies. This breed is often still used, as are Rottweilers and a few other breeds.

Chasing and holding

Most often, police dog refers to a dog who has been trained to guard their handler and to find, chase, intimidate, and hold suspects who are attempting to elude the police. Modern police dogs are not vicious animals; most are trained to enjoy their work, with chasing and grabbing introduced to them as tricks or games that can be played only when the handler (a police officer) gives the appropriate command. The dog's goal is not to bite; it is to grab and hold on at all costs until the handler gives the release command. This means that the dog grabs hard, and a fleeing suspect can be bitten when attempting to avoid or fight off a dog and the dog is attempting with full speed and energy to grab the suspect. Most handlers, if possible, give the suspect a verbal warning that the dog will be set loose if they do not immediately halt, and this is often sufficient deterrent that the dog is not needed.

Some police K9 units prefer to start with a pursue and bark tactic, where the dog barks to alert the handler to his whereabouts and to intimidate the suspect and keep him from running until the police arrive. In this case, the dog usually grabs and holds only when the suspect does not hold still after the dog's very verbal warning. Others feel that the bark first, bite later strategy is not effective and prefer to always use the chase and hold strategy.

Most of these dogs live in their handlers' homes and interact with their family and friends on a regular basis to ensure that they remain social and pleasant animals. This does not mean that it is acceptable to approach a police dog to pet it or play with it while it is on duty.

A police dog and handler train and work as a team, because they must trust each other and understand each other completely when working in stressful, even dangerous, and often rapidly changing situations. Police K9 teams have been accused of using excessive force in some cases, so it is critical that the human be able to manage a difficult situation wisely, to use his trained dog only as appropriate, and to be able to control the dog completely so that the dog can be called off instantly when the situation warrants.

In recognition of the valuable role these animals play in police duties and the dangers they face, there have been a number of measures to insure their protection. These include outfitting dogs with bulletproof vests to protect them from guns and some areas have passed laws that make attacking a police dog a felony.

Other law-enforcement uses

Law enforcement also uses dogs for tracking suspects or finding missing persons, or for detecting drugs or explosives. Bloodhounds are often used for the former, although most breeds have an outstanding sense of smell and can be trained to follow scent trails or to detect certain kinds of odors.

Some dogs, called cadaver dogs, are trained in detecting the odor of decomposing bodies. Dogs' noses are so sensitive that they are even capable of detecting bodies that are under running water.

For some sniffer dogs in environments where it is perceived that a criminal may attempt to kill the dog to prevent detection, a bodyguard dog is assigned with the sniffer to intimidate and, if necessary, attack anyone who would attack the sniffer.