Horses and dogs, although man’s best friends, do not always get along. A dog shown a horse for the first time will often bark and may even attack the horse. If the horse is being ridden on a road when startled by a dog, the results can be tragic.

The facts of the Ontario case of Moffat v. Downing, (1981) 32 O.R.(2d) 155 represent the classic example of what can occur when horses and dogs come into conflict. Two girls were riding their horses on a sideroad, while some children were playing with a dog on a grassy slope beside the road. The riders called to the children to restrain their dog, but they did not do so. The dog then ran towards the horses, barking and snapping at their heels. One horse reared up and threw its rider before turning onto the travelled portion of the highway, where it was struck by a car.

There are many cases both in Canada and England relating to dog attacks on horses and on people. As a result, the common law – the law developed by the courts – has developed applicable legal rules. At common law, the courts rely primarily on two separate but related legal doctrines: negligence and scienter.

Scienter: A little knowledge is an expensive thing

The doctrine of scienter states that where a person is in control of a domestic animal and has knowledge of a dangerous trait possessed by that animal, that person will be held strictly liable for any injury caused by the animal as a result of that trait. This doctrine can be used by a victim of an attack against the animal owner where the attacking animal was previously known to be vicious. It can also be used as a defence by an animal owner if the attacking animal had no history of violence. The scienter doctrine differentiates between “wild” (tigers, monkeys, snakes, etc.) and ‘domesticated’ (cows, horses, dogs, cats, etc.) animals. A defendant will be held liable for injury caused by a wild animal even if the defendant was unaware of any specific propensity for violence in the animal (Note: a 2009 B.C. case, McLean v. Thompsons 2009 BCPC 415, found that a wolf-dog hybrid was a wild animal due to its wolf heritage).

The doctrine of scienter was used in the Saskatchewan decision of Ross v. Vidnes (2012) S.J. No. 496. The defendant had a large St. Bernard that was known to be difficult to control and had been subject to several complaints of it running at large in the past. The plaintiff, a seven-year-old boy, was known to have provoked the dog on at least one occasion in the past by hitting it with a metal rod. One day the boy, who had been playing at the defendant’s house, came back to retrieve his skateboard. A window was missing near the screen door and the dog lunged through and bit the boy in the face. The defendant was held liable in scienter due to the defendant’s knowledge of the dog’s aggressive tendencies and the plaintiff’s prior provocation.

The doctrine of volenti non fit injura (Latin for “no injury is done to a person who consents”) can be successfully employed to defend cases where scienter may apply, but the injured party ignored warnings and assumed the risk of attack. In Laws v. Wright (2000) Carswell Alta 108, barn owners knew of the propensity of one of the horses stabled there to bite. When the horse in question bit the thumb of a rider, the stable was not held liable, because the experienced horsewoman who was bitten had disregarded barn rules by hand-feeding a horse other than her own.

Negligence on the owner’s part

At common law, a dog owner can also be liable for his dog’s actions if they are attributable to negligence on the part of the owner. For an action of negligence, it is enough that the dog owner knew, or ought to have known, of a potentially dangerous situation and did not take reasonable steps to control his dog so that the situation was avoided.

As an example, in Morsillo v. Migliano, (1985) 52 O.R.(2d) 319, a German Shepherd attacked a boy playing near the dog’s front yard. The dog was known to be vicious and so was usually led with a leash and choke collar when it was to be brought inside. On this day, the 13-year-old daughter decided to bring the dog inside while her parents were at work. She led the dog with a leash, but did not use a choke collar. The dog was too strong for her, got away, and attacked the boy, biting him several times. The court held the owners of the dog responsible for the injuries to the boy on the basis of negligence. The owners should have foreseen the likelihood of the dog, if it got loose, attacking the children. They had not properly instructed the daughter and were held to be negligent. This case has been cited through the years as good law.

In the Moffat v. Downing case mentioned at the beginning of this article, the owners were found negligent. The owners knew – or ought to have known – that the dog, playing by the side of the highway, could cause an accident if it ran up to horses and barked. They knew that horses were ridden on this particular road and they also knew that their dog did sometimes bark at horses. They had a duty to take steps to control their dog and their failure to do so was negligent. As such, they were liable for the damages to the rider and the car owner.

In addition to scienter and negligence, a person suffering injury or damage caused by a dog can make other common law claims against its owner such as nuisance, trespass, and occupier’s liability, depending on the facts surrounding the attack.

No longer entitled to “one bite”

Most Canadian provinces, with the exception of British Columbia, have introduced legislation that takes away the doctrine of scienter as a defence to a dog attack. Provinces and territories have introduced statutes that do away with the requirement of knowledge of viciousness for liability; much of this legislation is specific to dogs.

In Ontario, for instance, the relevant statute is the Dog Owners’ Liability Act, R.S.O.1990,c. D.16 (the “Act”). The Act goes well beyond the doctrine of scienter. Every dog no longer gets one bite; propensity to attack is no longer relevant to liability. So long as there is an attack, the owner is assumed to be liable for any resulting injuries (s.2(1)). “Owner” includes a person possessing or harbouring the dog, which can lead to some interesting findings of ownership. As owners are jointly and severally liable for damages (s. 2(2)), an injured party who fails to collect from one owner may collect the entire amount from any co-owners, including, for instance, a dog walker, if the Court considers him or her to be caught within the definition of “owner.”

It is still open to the owner to prove facts excusing him or her from liability. The Act also requires the court to reduce the damages awarded to the victims in proportion to the degree, if any, to which their own fault or negligence contributed to their damages (s.2(3)). Additionally, a dog owner who is liable to pay damages under the Act can seek contribution and indemnification from any third party (such as a dog-sitter) proportionate to their fault or negligence in contributing to the damages sustained by the victim (s.2(4)).

Case law shows just how onerous this type of legislation can be. In the Ontario case of Wong v. Arnold, (1987) 59 O.R.(2d) 299, the owners of a dog were found strictly liable under the older version of the Act when their dog lunged at the victim, causing him to jump back and fall over a wall onto the sidewalk, breaking his leg. The dog was on a leash on the owner’s veranda and the leash held the dog back when he lunged. Nevertheless, the owners were liable for the victim’s injuries – even though the dog did not touch him.

Horse owners and riders also shoulder some of the responsibility and should realize that to a lot of dogs, a horse is a potential threat. (For ways to introduce horses and dogs safely, go to Barn rules should include rules about the dogs of boarders and guests. Give dogs a wide berth where at all possible, and if a situation looks potentially dangerous, take steps to prevent trouble before it happens.

The legal information provided in this article is based on the laws of Ontario. If you find yourself in a situation to which this article may apply, please consult a lawyer before acting or relying on any of the statements made herein.

Willson Lewis LLP is a litigation law firm practising in civil litigation, employment law, construction, commercial disputes, family law, tax disputes, and equine law. Catherine Willson is a partner at Willson Lewis LLP with expertise in Equine Law; visit