Don't Start Your Own Fires: Expert Evidence in the Context of Negligence Cases

All lawyers learn about the tort of negligence in the first year of law school. Many practitioners, especially those practising in the areas of professional liability or personal injury, deal with the tort of negligence on a daily basis. For those who do not practice in those areas, deciding what evidence needs to be called can sometimes pose problems, even though the legal elements of negligence are ingrained in our heads.

One of the evidentiary issues that will almost always come up is the question of whether to call expert evidence regarding the standard of care. While in many cases, the need to call expert evidence goes without saying, there are cases where either the conduct is so patently negligent to the plaintiff or where the value of the claim makes it hard to swallow the not insignificant costs of hiring an expert.

The Ontario Court of Appeal’s decision in Metropolitan Toronto Condominium Corporation No. 110 v. A. & G Shanks Plumbing & Heating Limited (2020 ONCA 67) reinforces the notion that plaintiffs and their lawyers fail to call expert evidence regarding the standard of care at their own peril.

The Decision

The plaintiff, a condominium corporation, commenced an action against a plumbing company for the damages caused by a fire that had originated near the location of the plumber’s work shortly after the work had been completed.

The plaintiff did not call expert evidence on the standard of care because the plumber’s conduct was “egregious” and obviously fell below the standard. In response, the defendant did not call any expert evidence but adduced the evidence of the plumber who performed the work and who testified about the precautions he had taken.

The trial judge dismissed the plaintiff’s negligence claim on the basis that the plaintiff had not established conduct that fell below the standard of care and that the plaintiff had not established causation. In so doing, the trial judge held that the plaintiff should have led expert evidence to establish the appropriate standard of care.

The Court of Appeal upheld the trial judge’s decision. The Court of Appeal held that, since the plaintiff had failed to call expert evidence to show that the plumber’s precautions fell below the applicable standard of care, the trial judge was entitled to conclude that, considering all the direct and circumstantial evidence, the plaintiff had failed to establish a breach of the standard of care. Given this conclusion, the Court of Appeal did not address the issue of causation.


The exceptions to the requirement to call expert evidence regarding the standard of care are fairly established. The general rule is that a plaintiff should call expert evidence regarding the standard of care unless: (a) the impugned actions are so egregious that it is obvious that the defendant’s conduct has fallen short of the standard of care without even knowing precisely the parameters of the standard of care; or (b) where the evidence concerns non-technical matters or those of which an ordinary person may be expected to have knowledge.

Plaintiffs may proceed to trial without expert evidence believing that they will be able to establish that the impugned conduct was egregious or that it involves non-technical subject matter.

However, proceeding in this manner is fraught with uncertainty. Establishing that a defendant’s conduct is so egregious that the trial judge does not need to hear evidence from an expert is difficult, only being met in the worst of cases. Further, the jurisprudence regarding what is considered “non-technical” subject matter is limited, making it a discretionary determination that a trial judge will make based on the facts and circumstances of the particular case.

The Court of Appeal has made it clear that whether expert evidence is required to establish the standard of care will depend on the circumstances of the case. As such, it is prudent for lawyers prosecuting negligence claims regarding any subject matter to submit expert evidence. Betting on your ability to establish one of the exceptions to the requirement for expert evidence could leave a massive hole in your case