If you go into a hospital emergency room, it probably won't be long before you see someone come in with a dog bite injury. Every year, about 4.5 million people are bitten by dogs in this country. Almost 800,000 bites a year require some kind of medical attention. (These figures are from a federal Centers for Disease Control and Prevention factsheet.)

In most cases, the dogs' owners are responsible for footing the bill, because they have a legal responsibility to prevent their pets from injuring people or damaging property. If a dog hurts someone, the owner will probably have to reimburse the victim for medical expenses, time lost from work, and pain and suffering. The owner's homeowner's or renter's insurance policy may cover the cost, even if the injury happens off the owner's property.

The owner may also be required to take measures to prevent another incident—in the most serious cases, by destroying the dog. An owner who acts recklessly or deliberately—by letting an aggressive dog run loose around children, for example—may face a fine or even a jail sentence. (See “Dangerous Dogs.”)

Liability in a Nutshell

A dog owner may be liable for injury the dog causes if any of the following three things is true:

1. The owner knew the dog had a tendency to cause that kind of injury—the “one-bite rule.” This misleadingly named rule makes an owner legally responsible for an injury caused by a dog if the owner knew the dog was likely to cause that type of injury—for example, that the dog would bite. The victim must prove the owner knew the dog posed a danger.

EXAMPLE: A New Jersey man was scratched by a dog. He sued and won, based on the one-bite theory, because he proved that the dog's owner knew of the dog's tendency to jump up and scratch people. (Jannuzzelli v. Wilkens, 158 N.J. Super. 36, 385 A.2d 322 (1978).)

Learn more about the one-bite rule.

1. A dog-bite statute makes the owner liable. State dog-bite laws make owners responsible for almost any injuries their dogs cause, whether or not the owner knew the dog had a tendency to cause that kind of injury.

EXAMPLE: Barbara lives in Minneapolis with her spaniel-mix dog, Ray, who has always been gentle with people. But one day, while on a leash, Ray bites a child in a park. Barbara wasn't being careless, but her state's law makes her financially liable because her dog, without provocation, bit someone who was "acting peaceably" in a place he had a right to be.

Learn more about state dog-bite statutes.

1. The dog owner was unreasonably careless, and that's what caused the injury. If the injury occurred because the dog owner was unreasonably careless (negligent) in controlling the dog, the owner may be liable.

EXAMPLE: Lucy puts her new dog, Zippy, in the back yard but forgets to close the gate. The dog runs out into her front yard and bites the mail carrier. Lucy didn't know the dog would bite. But because her negligence—leaving the gate open—caused the injury, she is liable.

Learn more about negligence as it applies to dog owners.