Canada: Ontario Court Of Appeal Affirms Trial Judges As 'Robust Gatekeepers' Of Expert Evidence

Last Updated: March 10 2015
Article by Colin Chant

In the face of the trend in litigation towards an ever greater reliance on expert evidence, the recent Ontario Court of Appeal decision in Meady v Greyhound Canada Transportation Corp. 2015 ONCA 6 ("Meady") upholding a trial judge's decision to exclude the evidence of two of the plaintiffs' expert witnesses on the grounds that their evidence was not necessary, signals to litigants and lower courts alike the expectation that trial judges will act as robust gatekeepers to control the admission of expert evidence, and that their decisions to exclude expert evidence will be given deference.


In December of 2000, Shaun Davis, a 21-year-old passenger of a Greyhound bus driving through Northern Ontario, left his seat and grabbed the steering wheel from the bus driver, causing the bus to veer off the road and topple on its side, killing one passenger and injuring many others.

Mr. Davis suffered from paranoid delusions, and prior to boarding the bus had interacted with two OPP officers who found him to be displaying signs of anxiety and paranoia but who nonetheless concluded that he did not pose a threat to anyone. The police officers told the bus driver about Mr. Davis' paranoia; however, the driver allowed Mr. Davis to board the bus, and let him sit up front.

After the accident, a number of the passengers commenced an action naming Greyhound, the bus driver, the two OPP officers and the OPP.

The matter went to trial in 2010, and after 65 days of evidence from 83 witnesses, Justice Platana dismissed the action against all of the defendants except Davis.

The plaintiffs appealed.

At issue on the appeal was the decision by Justice Platana at trial to exclude the evidence of two expert witnesses tendered by the plaintiffs: a retired police officer who opined that the OPP officers had failed to meet the standard of care of reasonable and prudent officers by failing to detain Mr. Davis under the Mental Health Act or the common law doctrine of investigative detention; and a transportation safety consultant who had experience as an accident investigator and in drafting policies and standards for training bus drivers who opined that the bus driver was negligent in his operation of the bus.

Exclusion of Expert Evidence at Trial

At trial, Justice Platana excluded the evidence of the retired police officer on the basis that while expert evidence concerning the standard of care of professionals such as police officers may be required in some cases, it was not required where the issue falls within the understanding or experience of the trier of fact, and that because evidence regarding police policies and procedures was adduced into evidence, the officers could be cross-examined on their compliance.

Justice Platana found the evidence of the transportation safety consultant relevant but excluded it as unnecessary, after concluding that he did not need expert evidence to determine what the driver knew or ought to have known about his duties as an operator, how fast he should have been driving, how he should have reacted to Mr. Davis grabbing the wheel or the steps he could have taken to avoid the accident. Justice Platana also noted as a factor in his decision to exclude the evidence that the consultant had expressed an opinion on the ultimate issue by specifically stating in his report that the bus driver was negligent in the operation of the bus.

Principles Governing the Admissibility of Expert Evidence

The test governing the admissibility of expert evidence was articulated in the Supreme Court of Canada's decision in R v Mohan where the court held that expert evidence:

  1. must be relevant;
  2. must be necessary to assist the trier of fact;
  3. must not be subject to an exclusionary rule; and
  4. the expert must be properly qualified

At issue in Meady was whether the proposed expert evidence was necessary to assist the trier of fact.

The application of the necessity criterion asks whether the trier of fact is able to form a correct judgment about the issue without the assistance of persons with special knowledge.

In considering necessity, the Court of Appeal noted the growing recognition of the responsibility of trial judges to exercise a more robust gatekeeper role in the admission of expert evidence, and the admonition by the Supreme Court in Masterpiece Inc. v Alavida Lifestyles Inc. that unnecessary expert evidence distracts triers of fact from the issues at hand, complicates the proceeding, prolongs the trial and increases the cost of litigation. The Court also cited the growing importance of "trial economy", and the need for judges to conduct a cost-benefit analysis when considering whether to admit evidence.

The Court further held that because there is no "bright line" to determine whether the subject matter of expert evidence falls within the normal experience of a particular trier of fact, deference is owed to the exercise of the trial judge's gatekeeper function in excluding unnecessary evidence. The trial judge is best equipped to appreciate the issues in the context of the evidence as it unfolds and to determine the extent to which, if at all, expert evidence is required to assist the trier of fact in the disposition of the issues.

Reasons for Judgment

In applying the principles outlined above, the Court of Appeal found that Justice Platana was uniquely positioned to decide whether he needed expert evidence, and that his rulings on the excluded evidence attracted deference.

With respect to the retired police officer, the Court found that the exercise of police powers of investigation, arrest and detention are "part of the daily diet" of Superior Court judges and it was open to Justice Platana to conclude, as he did, that expert evidence was not required for him to determine whether the OPP officers in question should have conducted further investigation of, restrained or otherwise diverted Mr. Davis from boarding the bus.

The Court also held that Justice Platana had reasonably excluded the evidence of the transportation safety consultant and issues similar to those raised by the consultant were frequently decided in motor vehicle negligence cases without the assistance of expert evidence, and his conclusions regarding the bus driver's actions were available to him on the evidence before him and could be decided without expert evidence.

The appeal was dismissed.

Why the Decision Matters

The Court of Appeal's decision in Meady strongly that suggests that trial judges will be casting an increasingly critical eye on whether to exclude the evidence of persons proffered as experts at trial and that their decisions in this regard will be given deference by higher courts.

The decision also serves as a stark reminder that just because an expert has evidence that is relevant does not mean that it will always be necessary.

Parties preparing for trial would do well to take note of this decision.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

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