Slipping into Irrelevance: The Ontario Court of Appeal Provides Further Clarification on the Admissibility of Expert Evidence in Jury Trials
In Pederson v. Forget, 2026 ONCA 118, the Ontario Court of Appeal provided further guidance on the admissibility of expert evidence in jury trials. The Court also provided insight into when a trial judge’s exclusion of evidence constitutes a “miscarriage of justice.”
Factual Background
This case was an appeal from a negligence action tried before a jury. The respondents were found not liable at trial.
Ms. Pederson, the appellant in this case and the plaintiff below, had slipped on a wooden staircase in a residential home. Mr. and Ms. Forget, the respondents and defendants below, were the owners of the home. The trial focused on whether the Forgets were negligent under the Occupiers’ Liability Act, R.S.O. 1990, c. O.2.
The trial turned on the maintenance of the wooden staircase. Ms. Pederson maintained that she heard the Forgets discussing, in both English and French, the use of a cleaning product called Pledge on the stairs. She further maintained that the Forgets employed a cleaning lady who cleaned the stairs.
The Forgets maintained that they did not employ a cleaning lady, and that they cleaned the stairs with Vim, a product intended for cleaning wooden floors and stairs.
A key issue at trial was the relative credibility of the parties.
Each side called expert evidence regarding the slip resistance of the staircase when cleaned with various cleaning products. Both experts had an opportunity to test the Forgets’ staircase at issue, although Ms. Pederson’s expert was concerned about alleged tampering with his tests. Although both experts were qualified by the trial judge, the first round of testing conducted by Ms. Pederson’s expert, which was not conducted at the Forgets’ home, was excluded.
The appeal turned on the exclusion of that evidence.
Analysis
The Court considered two issues: whether the trial judge erred in excluding the first set of testing and whether any error resulted in a miscarriage of justice.
The determination of whether the exclusion was appropriate turned on the application of the two-part test for admission of expert evidence set out in White Burgess.[1] For reference, the test is as follows:
- Does the expert evidence meet the threshold requirement for admissibility;
- If the expert evidence meets the threshold, has the trial judge appropriately exercised their gatekeeping function and balanced the risks and benefits of admitting the evidence?
The trial judge had little difficulty finding that the threshold stage of the White Burgess test was met. The evidence was relevant and necessary. However, when exercising his gatekeeping function, the trial judge excluded Ms. Pederson’s expert’s first round of testing, finding it was unreliable. The tests were conducted on a different type of wood, used a different dilution of cleaner, were conducted much closer to the application of the cleaner, and did not test the same materials as were involved in the accident.
The Court upheld the trial judge’s findings. In particular, the Court stressed that it is “the role of the trial judge to ensure that the task of the jury is as straightforward as possible,” particularly in cases where a jury may otherwise by swayed by an expert’s apparent authority. As the Court stated, a trial judge’s role is to be vigilant that experts testify only within the confines of their qualifications.
The Court dismissed concerns about tampering at this stage of the analysis, holding that “possible tampering was a factual determination to be made and was distinct form the qualification” of Ms. Pederson’s expert.
The fact that the exclusion was not an error was determinative. However, the Court also considered whether the exclusion would have caused a miscarriage of justice.
The Court held that any exclusion did not result in a miscarriage of justice. The parties’ credibility, not the expert evidence, was determinative at trial. Moreover, the tampering allegations were put before the jury, and the jury was provided with enough evidence to assess the allegations. As the Court held, the admission of the first report “would not have made a difference to the outcome of this case.”
Disposition of the Court
The Court dismissed the appeal. The trial judge did not err in excluding the evidence and, in any event, there was no miscarriage of justice.
Takeaways
This decision reaffirms the important gatekeeping role of trial judges when assessing expert evidence. The role of a trial judge includes ensuring that expert evidence remains relevant, reliable, and within the bounds of the expert’s qualifications.
In particular, this decision reiterates that the role of a judge in a jury trial is to ensure that the jury’s task is as straightforward as possible. This includes the responsibility of managing evidence appropriately.
Finally, this decision reaffirms that a finding of a miscarriage of justice requires more than just the possible mishandling of evidence by a trial judge. The trial judge’s decision regarding that evidence must make a difference in the outcome of the case.
[1] White Burgess Langille Inman v. Abbott and Haliburton Co., 2015 SCC 23.