Who has to prove their case in an Ontario civil lawsuit?

In Ontario civil litigation, the general rule is that the party making a claim bears the burden of proving it. This means the plaintiff — the person who started the lawsuit — must prove the facts that support their claim. In a defence, if the defendant asserts an affirmative defence (such as a limitation period, contributory negligence, or consent), the defendant bears the burden of proving those specific facts.

The standard of proof in Ontario civil cases is the balance of probabilities, sometimes expressed as "more likely than not." This means the plaintiff must demonstrate that it is more probable than not — greater than 50% likely — that the events occurred as they claim and that the defendant is responsible. This is a lower standard than the criminal standard of proof beyond a reasonable doubt.

The burden does not shift simply because the other side denies the claim. If a plaintiff presents evidence and the defendant says nothing, the court weighs the evidence presented. If the plaintiff's evidence establishes the facts on a balance of probabilities, the plaintiff will succeed. Courts in Ontario are entitled to draw reasonable inferences from the evidence presented — a plaintiff does not need direct evidence of every element of a claim, as long as the totality of the evidence makes the claimed facts more probable than not.