Not every complaint against a veterinarian is necessarily a malpractice case. If you're considering a malpractice action, check to see if your situation falls into one of the categories discussed here. But be warned that this short list doesn't come close to covering all the possible kinds of lawsuits veterinarians might come in for. If you have a situation that doesn't fit in any of these pigeonholes, you may want to find out your options from a lawyer.
If your dog dies at the vet's, and you don't know why or how—or what happened at all—the law in most states helps you by making the vet responsible for proving that the death wasn't caused by malpractice or negligence.
The way you take advantage of this rule is by suing for negligent bailment. "Bailment" is the legal term for the relationship that results when some item of property—in this case, a dog—is left in someone else's care. Under the law of bailment (which may vary from state to state), if a dog is left with a vet and the dog dies, the vet is presumed, legally, to be negligent. The vet must then prove otherwise or be liable to the dog's owner for the value of the dog.
EXAMPLE: A woman boarded her healthy, eight-year-old dog with a New York veterinarian. When she returned two weeks later, she was told the dog had died a few days before. The vet gave no satisfactory explanation of the dog's death, so the owner was entitled to recover the value of the dog. (Brousseau v. Rosenthal, 443 N.Y.S.2d 285 (1980). See also Price v. Brown, 651 A.2d 548 (1994) (owner whose dog died at vet's after surgery could proceed with bailment lawsuit).
A veterinarian who takes your dog without permission is liable to you for the value of the dog. The vet may also be guilty of theft, but that's a criminal matter to be handled by the police and district attorney. You can bring a civil lawsuit for "conversion."
EXAMPLE: An Oregon woman asked a vet to humanely destroy her dog, which had been shot and was in extreme pain. Instead, the vet gave the dog to two assistants who had grown attached to it. The original owner sued when she found out, and was awarded $500 for the vet's conversion of the dog. She was also awarded $4,000 for her mental anguish and $700 in punitive damages (extra damages awarded to punish wrongdoing). (Fredeen v. Stride , 525 P.2d 166 (Or. 1974).)