Dog Bite law is a unique combination of city and county ordinances, state statutory law, state case law (i.e., legal principles that result from specific lawsuits within the state), and common law (i.e., legal principles resulting from specific lawsuits from throughout the United States, usually as reported in authoritative legal works such as the Restatement of Law).

Broadly speaking, all states hold a person responsible for (a) their own negligence, intentional conduct, and reckless or outrageous behavior, (b) keeping a dog that previously bit a person or exhibited a tendency to someday bite a person (called "common law strict liability"), and (c) violating a public health and safety law such as a leash law or a prohibition against dogs running at large. In all state law strict liability states (i.e., those that have strict liability statutes applicable to canine inflicted injuries), the dog owner will be held liable upon the additional ground that he was the owner of the dog that inflicted the bite, without regard to whether he was negligent or anything else. Some strict liability statutes include whoever had custody of the dog as well as its owner, non-bite injuries as well as bites, and provide for additional compensation if the dog previously bit a person. Many dog bite statutes combine concepts of negligence, common law strict liability, and violations of local law. Thirty states have dog bite statutes.

The usual defenses in dog bite claims are that the victim provoked the dog, was a trespasser, was negligent, consciously assumed the risk of being bitten, or was a canine professional who was deemed to assume the risk. When the victim is a child, another defense is that his parent negligently failed to supervise him, and therefore was a cause of the accident. These defenses might be based on state statutes or judicial decisions. The defenses are different from state to state, and any particular defense might not apply in a specific case.

When the state does not have a strict liability statute.

If a state does not have a strict liability statute, that state is a "one-bite state." In "one-bite states," legal responsibility is determined by the following principles:

The first issue is whether the dog previously bit anyone. If so, then the dog owner / custodian is strictly responsible.
If the answer is no, the second issue is whether the dog previously did something that should have put the owner / custodian on notice that the dog was inclined to bite somebody in the future.
If that answer is no, we consider whether the person having custody of the dog at the time of the incident had violated any law pertaining to public health or safety, which was intended to protect people like the victim. An example would be a leash law, but there could be regulations such as those that restrict dogs from being in day care centers are beauty parlors. The violation of such a law would be considered "negligence per se." In some states, like Georgia, the violation is not negligence per se but rather an alternate way of proving liability under the dog bite statute.
If we cannot find negligence per se, we consider whether the accident was caused by negligence. For example, a dog that is habitually mistreated, or sick, or suffering from a painful disease is more likely to bite a person, even if the dog has never done so before. Negligence is usually a ground for liability in a "one-bite" state.
If the dog owner or custodian is not responsible, then we consider whether anyone else might be liable as a result of their negligence or knowledge of the dangeous propensity of the dog to bite people.

When the dog owner does not have insurance.

If the dog owner is unable to compensate the victim because of lack of insurance or resources, attorneys consider whether anyone else might be responsible because of their own negligence. An example would be a landlord who knows that a dangerous dog is living with a renter, but fails to do anything to control the dog or its owner.