The essence of common law strict liability is the dog owner's knowledge that the dog had a dangerous propensity. The victim can prove that the dog had a dangerous propensity in a variety of ways, some of which are listed above. However, proof of merely the propensity is not sufficient to hold the dog owner liable; the victim also has to prove that the dog owner knew or should have known that the dog had done the things that established the propensity.
The action of the dog that injured the victim in the current case must be essentially the same as the action that the dog owner previously knew or should have known of. In other words, one who knows that his large dog likes to jump on people will be charged with knowledge of a dangerous propensity (i.e., the tendency to jump upon and possibly knock a person down), but knowledge of this particular dangerous propensity will not help establish the claim of a person who was bitten by the dog. To put it yet another way, the victim must prove that the dog owner had prior knowledge of the dog's tendency to do essentially the same thing that later caused injury to the victim. As noted legal scholar William Prosser said, the prior act "must extend to the trait or propensity which caused the damage." W. Prosser, Handbook of the Law of Torts, § 76 (4th ed. 1971).
Courts have held that the testimony of an expert witness can be helpful with regard to the scienter requirement. For example, in the Diane Whipple case, expert testimony was admitted to prove that the escalating series of acts by the dogs were a clear tip-off that they were headed toward committing serious violence against a person. However, courts also have held that expert testimony alone cannot establish the subjective knowledge of the dog owner. For example, in Kathren v. Olenik, 46 Or.App. 713, 718, 613 P.2d 69 (Or.App. 1980) the court stated:
Plaintiff argues the opinion of the expert that Mordecai was vicious and would have been vicious for several months is sufficient to allow the jury to find that defendants should have known of the dog's temperament. That opinion may have been evidence that the dog was in fact vicious, but it is not evidence that the defendants actually knew of the propensity or were aware of any manifestations of viciousness that would put them on notice. The burden was on plaintiff to prove the dog was vicious and that defendants knew of the dog's propensity.
An interesting issue arises where the dog owner admits that his dog previously bit a person, but claims that the prior victim provoked the dog. This issue was addressed in Reynolds v. Reichwein (1973) 510 P.2d 895, 1973 Colo. App. Lexis 857, in which the Court of Appeals of Colorado held that the appellate courts will not overturn the trier of fact's determination that that owner knew his dog was vicious, as long as the determination finds some support in the record. In Reynolds, the dog previously bit a child that provoked it. Despite the provocation, the trial court ruled that the dog was vicious and the owner knew or had notice of the dog's vicious tendencies.
The following facts were held to support a finding of knowledge of the dangerousness of a dog:
- The dog is kept as a guard dog. Portillo v. Aiassa (1994) 27 Cal.App.4th 1128, 1135; Bulow v. Dawn Patrol (1963) 216 Cal.App.2d 721, 728-729.
- The dog is kept tied up: this has been proven to be a cause of viciousness.
- The dog is muzzled around people.
- People are kept away from the dog. Northon v. Schultz (1955) 130 Cal.App.2d 488.
- There is a "Beware of Dog" sign. Portillo v. Aiassa (1994) 27 Cal.App.4th 1128, 1135.
- The owner warns people that the dog may bite. Bulow v. Dawn Patrol (1963) 216 Cal.App.2d 721, 729.
- The owner brags that the dog attacks people.
- There is a newspaper article posted on the premises, describing the dog essentially as an attack dog. Portillo v. Aiassa (1994) 27 Cal.App.4th 1128, 1132.
- The dog is a Husky that runs and attacks the front fence, growls, barks, shows it teeth, tries to bite through the fence, tries to jump the fence. Dixon v. Frazini (1992, 4th Dept.) 592 NYS2d 208, 188 AD2d 1054. It was held that the jury could find that the landlord had notice because she was the sister of a tenant and visited the tenants to collect rent and for family visits.
- The owner's or keeper's knowledge of a dog's vicious or dangerous propensities may be inferred by the following evidence: (1) the general reputation of the dog, (2) the size and breed of the dog, or (3) the fact that the dog is kept chained or muzzled. Smith v. Royer (1919) 181 Cal. 165, 170; 1 California Torts (1994), "Strict Liability -- Animals," sec. 6.10, p. 6-10.
- See also the cases holding that certain actions of the dog were sufficient to prove the dangerous propensity, in the prior section.