Dog bite laws vary from state to state. The law of most states follows a "strict liability" theory. Under these statutes, the dog owner is responsible for any damage caused by an attack from their dog. In other states, in order for the owner of a dog to be liable to a person injured, the plaintiff must prove that the dog was vicious or had a natural inclination or tendency to be dangerous and that the owner had knowledge of such a tendency. Viciousness may typically be established by testimony regarding past attacks, past complaints, and methods of confinement. The following is an example of a state statute defining a vicious animal. State laws vary, so local laws should be consulted for requirements in your area:
“Vicious animal” means any animal, except for a dangerous animal per se, as previously listed, that has bitten or clawed a person or persons while running at large and the attack was unprovoked, or any animal that has exhibited vicious propensities in present or past conduct, including such that said animal
(a) has bitten or clawed a person or persons on two separate occasions within a twelve-month period; or (b) did bite or claw once causing injuries above the shoulders of a person; or (c) could not be controlled or restrained by the owner at the time of the attack to prevent the occurrence; or (d) has attacked any domestic animal or fowl on three separate occasions within a twelve-month period, or any animal which has been found to possess such propensities by the Council, after hearing."
More than 4.5 million people, including 2,000 mail carriers, are bitten by dogs each year, according to the Postal Service. It the official policy of the U.S. Postal Service to try to prevent dogs from biting their employees. However, the dog's owner is held responsible if a dog bites or injures a postal carrier. Mail carriers are issued pepper spray to use if threatened by a dog. If they use the spray, they have to inform the dog's owner. The owner can hold the carrier responsible if the dog is harmed by the spray.