Dog owners can usually be held liable when their dogs cause injuries to other people. This is true whether the dog bites someone, or otherwise causes injury or damage to property. Sometimes, a fair settlement of the issue can be reached without having to file a lawsuit, but often the injured party will need to sue the dog owner to hold him or her liable to the full extent that the law allows – or to get an insurance company to move on the case.
This article touches on some of the key legal and practical issues involved, and offers links to more in-depth information on the laws involved.
The short answer is that you should file a lawsuit against a dog owner when you have a valid case -- whether it's for a dog bite injury or some other loss caused by the dog -- and when the potential result would be worth your time and money.
A dog owner can be held responsible when his or her dog's behavior leads to injuries or property damage, but the extent of the liability and what needs to be proven in a legal case varies from state to state.
In some states, the dog owner is subject to strict liability, meaning that fault on the part of the dog owner does not need to be established if the dog bites someone. In these states, a few questions usually need to be resolved before the dog owner will be liable -- such as whether the person who was bitten was lawfully on the property where the bite occurred, and whether he or she did anything to provoke the dog.
Other states follow a "one bite" or negligence rule, where the focus is on whether the owner knew or should have known that the dog might bite, and whether the owner took necessary precautions based on that knowledge.
See "One-Bite" vs. Strict Liability Rules for Dog Bite Injury Cases for more detail and the differences in laws by state.
The dog's owner may very well be liable for your injuries or other damages, but from a practical standpoint, you need to ask yourself whether pursuing a legal remedy will really be worth the time, money, and effort. If you were nipped on the hand and hand a puncture wound treated at the ER, you might want to think twice about making a claim. On the other hand, if you've suffered significant injuries or other losses -- a dog attack costs you thousands of dollars in livestock, for example -- then filing a lawsuit is probably a good idea.
One final note on "when to sue": Your state has a personal injury statute of limitations that sets a limit on the amount of time an injured person can wait before filing their case in the state’s civil court system. If you’re thinking about filing a lawsuit over dog bite injuries, you need to pay attention to and abide by this deadline.
See AllLaw’s section on Animal and Dog Bite Injury Laws to find the dog bite injury liability rules and time limits for each state.