Strict liability, with a real evidentiary bar
Under Civil Code article 2321, a dog owner is strictly liable for injuries the dog caused that the owner could have prevented, and which did not result from the victim's provocation. Courts have interpreted "could have prevented" to require the victim show the dog presented an unreasonable risk of harm — a real showing, not just proof a bite happened. For animals generally (not dogs specifically), the article instead requires the more familiar negligence-style showing that the owner knew or should have known of the risk and failed to use reasonable care; dogs get the strict liability carve-out.
Provocation isn't just a judge-made defense here — it's written directly into the statute, excluding injuries that resulted from the victim provoking the dog. A handler's violation of a leash law or animal control ordinance can also support a separate negligence claim.