What is the test for determining whether a dog owner can be held liable for failing to prevent a visitor from being injured by his dog?

The district court correctly relied on Hagen v. Laursen, 263 P.2d 489 (Cal.Ct.App.1954) in reaching its conclusion. In that case, a California court reversed a jury verdict holding a dog owner to be negligent for failing to prevent her dog from accidently running into a visitor while playing, thereby causing an injury. The court held that the dog owner could not be held liable in negligence where she could not have anticipated nor prevented the accident. Id. at 492. The court held that to be liable for negligence there must be "reasonable anticipation of the occurrence and reasonable opportunity to act." Id.