Denis Grigoras

Denis is a lawyer who draws on his background in complex legal disputes and transactions to problem-solve for his clients.

Before the introduction of Ontario’s Dog Owners’ Liability Act, the common law dealt with dog bites/attacks on the basis of scienter (knowledge) or negligence.


Under the theory of scienter, the owner or keeper of the dog had to have knowledge or awareness that the animal was dangerous.  The person seeking damages for a dog bite/attack (the “Plaintiff’) had to prove that the dog in question inflicted the injuries, that the said dog had a mischievous or vicious propensity to commit the particular injurious act, and that the owner or keeper of the dog knew of such propensity.

If the owner or keeper of the dog had knowledge of a particular kind of mischief on the part of the dog, that person then had an absolute duty to prevent the dog from doing that kind of mischief and would be liable without proof of negligence.  It would be sufficient if the owner or keeper knew that the dog had a propensity or manifested a trait to do that kind of harm. 

For example, let’s say a dog had never previously bitten or attacked anyone, and then it ends up biting a child.  The owner or keeper would be found to have had knowledge of some special propensity if she or he knew that the dog was capable of spontaneous action in situations where it is not used to children being around.


The common law also allowed someone to launch a negligence claim against a dog’s owner or keeper.  The Plaintiff had to prove that the dog’s owner or keeper owed the Plaintiff a duty of care, that the owner or keeper breached the standard of care of a reasonable person in the circumstances, and, because of that breach, the Plaintiff suffered reasonably foreseeable injuries.  In such a negligence claim, the defence of contributory negligence was allowed – if the dog’s owner or keeper could demonstrate that the Plaintiff voluntarily assumed both the physical and legal risk involved in the activity, it was a complete defence to the Plaintiff’s negligence action. 

For example, where the dog owner or keeper warns the Plaintiff not to pet the dog and the Plaintiff pets the dog anyways (and gets bitten/attacked), the owner or keeper of the dog would have raised contributory negligence as a complete defence to the Plaintiff’s negligence claim.

Family Law Act Claims

A family member of a person injured by a dog bite/attack can also claim damages under s. 61 of Ontario’s Family Law Act.  Recovery can include pecuniary and non-pecuniary damages.

The Dog Owners’ Liability Act

Ontario modified all of this with the introduction of the Dog Owners’ Liability Act.  Now the law is that the owner of a dog in Ontario, or a person who harbours or possesses a dog, is liable for damages resulting from a bite/attack by that dog on another person or domestic animal.  The liability of the owner or harbourer does not depend on the knowledge of the propensity of the dog or on the fault or negligence on the part of the owner

This is called strict liability which means that liability is automatically imposed on the owner or a person who harbours or possesses a dog without a finding of fault.  However, the court must reduce the damages awarded in proportion to the degree (if any) to which the fault or negligence of the Plaintiff caused or contributed to the damages.

In light of this legislative modification to the common law, and with the imposition of strict liability, caution is always recommended whenever you are walking your dog and there are other dogs or people in the area.

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