With nearly 90 million pet dogs in the U.S. and about 4.5 million dog bites every year, it's no surprise that lawsuits over the resulting injuries are also common. Depending on the circumstances and where the injury happened, the victim may file a civil suit based on the dog owner's negligence or on a "strict liability" dog-bite law that makes the owner liable regardless of the animal's history or the owner's carelessness. But in some states without dog-bite laws, victims can turn to a common-law principle known as the "one-bite rule," which holds owners responsible for injuries only if they knew or should've known that their dogs were vicious or dangerous.
The term "one-bite rule" can be misleading. It doesn't mean that every dog owner is entitled to one "free" bite. Behavior other than a bite or attack can put an owner on notice that the dog poses a particular kind of risk (more on that below). If the animal goes on to hurt someone in that way, the owner—or the owner's insurance company—will probably have to compensate the victim for medical expenses and other damages.
Even in a state with a strict liability law, the one-bite rule may come into play if the statute doesn't apply under the circumstances—for example, if it covers only bites, and the dog caused an injury by chasing a bicycle.
The fact that a state doesn't have a strict liability statute doesn't necessarily mean that the one-bite rule applies. In Pennsylvania, for instance, courts have held that even when owners knew their dogs were vicious, they weren't liable for injuries caused by the animals unless they were also negligent (Deardorff v. Burger, 606 A.2d 489 (Pa. Super. Ct. 1992)).
If the owner denies responsibility and the dispute ends up in court (most don't), the judge or jury will have to decide whether or not the owner should have known the dog was likely to hurt someone. When making this decision, the court will take into account certain facts about the dog's history. (And in cases that don't go to trial, insurance companies and lawyers consider the same factors before they make settlement offers.) Among these considerations:
Previous bites. It may be obvious that if a dog bites once, the owner will forevermore be on notice that it's likely to happen again. But this guideline isn't as straightforward as it may appear. For example, if a puppy nipped someone, the court may find that its owners weren't necessarily on notice that the dog was dangerous (see Tessiero v. Conrad, 588 N.Y.S.2d 200 (App. Div. 1992)).
Barking at strangers. If a dog barks at strangers but has never been menacing, its owner will probably not be liable when it bites someone. (See, for example, Collier v. Zambito, 807 N.E.2d 254 (N.Y. Ct. App. 2004).)
Threatening people. A dog that often growls and snaps at strangers who come near it when out in public, but hasn't actually bitten someone, is a different case entirely. The dog's actions should put its owner on notice that the dog might bite someone. (See, for example, Fontecchio v. Esposito, 485 N.Y.S.2d 113 (1985).)
Jumping on people. The owner of a playful, large dog that's in the habit of jumping on house guests could be be liable if the animal knocks over a friend who comes to visit. The owner should know that the tendency to jump could be dangerous. (Drake v. Dean, 19 Cal.Rptr.2d 325 (Cal. Ct. App. 1993).)
Chasing people. If a dog likes to chase bicyclists or motorcyclists, the owner may be liable if the dog causes an injury while doing something similar.
Fighting with other dogs. If a dog is gentle with people but has a history of fights with other dogs, that's probably not enough to put the owner on notice that the dog might bite a person. Courts usually recognize that canine society has its own rules, and the way a dog behaves around other dogs isn't a reliable predictor of how it will act toward humans. If a dog has been trained to fight, however, a court will probably conclude that the owner should know the animal could be dangerous.
Complaints about the dog. An owner will almost certainly be on notice that a dog is dangerous if neighbors or others complain that the animal has threatened or bitten someone. But the nature of the complaints matters. In an Alabama case, for example, a court ruled that a dog owner didn't know (or have a reason to know) that his dog was dangerous just because a neighbor had told him the animal was "nuisance" (Rucker v. Goldstein, 497 So. 2d 491 (Ala. 1986)).
The dog's breed. Generally, courts don't consider dogs of certain breeds to be inherently dangerous. So if you have a German shepherd, a court probably won't conclude that you should have known it might injure someone just because of the dog's breed. (See, for example, Roupp v. Conrad, 287 A.D.2d 937 (N.Y. App. Div. 2001).) But some states and municipalities have breed-specific laws that define pit bulls and a few other breeds as dangerous dogs. Even without a rule like that, if a dispute goes to court, the result will depend on the facts and the judge or jury's attitude. Large dogs of breeds popularly believed to be dangerous, such as Dobermans, German shepherds, and pit bulls, may be judged more severely than dogs of cuddlier breeds.
"Beware of Dog" signs. Don't worry that putting up a warning sign is tantamount to admitting that your dog is a menace, landing you in bigger trouble if the dog does ever hurt someone. First of all, the sign will help avoid bites—which is far preferable than winning a legal battle over a bite later. Second, if you think your dog might hurt someone, there's almost certainly other evidence of the dog's dangerousness besides the fact that you put up a warning sign. And third, many homeowners use these signs in the hope that they'll ward off trespassers, even if their dogs have no history of being dangerous.
Even if the dog had a history of aggressiveness, its owner may be able to escape liability by proving that the injured person provoked the dog, voluntarily risked injury, or was trespassing on private property where the dog was properly confined. (See "A Dog's Owner's Legal Defenses" for more.)
The rules on liability for an injury caused by a dog vary from state to state. The outcome of any case depends on how the law (including state court decisions) applies to the particular circumstances. Whether your dog has hurt someone or you're the injured person, consider speaking with a personal injury attorney who can help you protect your rights.