In the Winter 2023/2024 edition of The Litigator, the quarterly journal of the Ontario Trial Lawyers Association, Paul published “From Start to Finish: How to Ensure Your Expert is Permitted to Testify at Trial.” The article is a practitioner-facing guide written for OTLA members on the practical realities of expert evidence in personal injury and medical malpractice trials. The article was drafted in September 2023 and appears in the Winter 2023/2024 issue. Paul was a partner at Will Davidson LLP at the time of writing.
The piece is structured around a single core insight from trial work: finding an expert who will write a favourable report is relatively easy, but ensuring that expert can withstand the qualification stage and the defence’s attempts to restrict the scope of their testimony at trial is much harder. The article walks plaintiff-side practitioners through the full life cycle of expert evidence: choosing the right expert, understanding the types of experts a party can call, navigating the qualification stage, and anticipating the defence strategies most commonly deployed to exclude or restrict expert testimony.
The strong-report-weak-witness problem
The article opens with a candid observation. Expert evidence is the foundation of every successful personal injury action. In straightforward cases, expert evidence is required to prove damages. In more complex cases, including medical malpractice and product liability, expert evidence is required to prove liability as well. The risk that plaintiff-side counsel needs to guard against is the strong-report-weak-witness problem: an expert produces a written report that says everything the case needs, and then, at trial, the same expert is sidelined, restricted, or poorly received by the trier of fact under the strict judicial scrutiny that defence counsel will bring.
The article’s purpose is to help plaintiff-side practitioners avoid the most common pitfalls. The structure is sequential: choose the right expert, understand the doctrinal framework that governs which experts can give which kind of evidence, prepare for the qualification motion, and anticipate the defence’s attacks.
Finding the right expert
The article identifies three considerations that should guide the choice of expert.
The first is experience with the subject matter. For physician experts, the key questions are whether the expert treated patients with the type of condition at issue around the time of the alleged negligence, how often they did so, and whether the work was done in Ontario. A cardiologist whose practice is in a tertiary academic centre may not be the right standard-of-care witness for a community emergency department case. The mismatch is not a fatal one, but it is the kind of issue defence counsel will exploit at qualification.
The second is experience as an expert. Counsel should know whether the proposed expert has testified before, whether they have ever been disqualified from giving expert evidence, and whether there are negative judicial findings on the record. Counterintuitively, less experience is sometimes better. Frequent flyers in the courtroom can be negatively received as professional witnesses whose objectivity is in question. The article’s point is that a careful, considered selection of a less-experienced expert with strong subject-matter credentials may be a stronger trial witness than a well-known expert with a long courtroom history.
The third is communication style. The article suggests a Zoom meeting and small talk with the prospective expert before any commitment is made. Counsel should assess whether they like the expert, whether the expert will come across as intelligent and knowledgeable without arrogance, and whether the expert has what the article calls “favorite professor vibe.” The jury or the judge will be deciding the case on the persuasiveness of the expert’s testimony, not on the credentials on the CV.
The article also makes a point about audience awareness. Whether the case is a jury or a judge-alone trial, the trial judge remains the gatekeeper of expert evidence. The mistake of assuming that a jury will see questionable expert evidence is one of the more dangerous misconceptions in personal injury practice. If the expert cannot get past the judge on qualifications or scope of testimony, the jury will never hear the evidence.
Types of experts: the Westerhof framework
The doctrinal anchor for the types of experts a party can call is Westerhof v Gee Estate, 2015 ONCA 206. The Court of Appeal for Ontario recognized three categories: litigation experts, participant experts, and non-party experts.
Litigation experts are retained by a party for the purpose of giving opinion evidence. They are the conventional expert witness: hired, instructed, prepared, and called to give an independent professional opinion on the issues in dispute.
Participant experts are witnesses whose evidence is derived from their observations or involvement with the underlying facts and whose opinions are formed in the ordinary exercise of their skill, knowledge, training, and experience while observing or participating in the events at issue. The most important participant expert in a personal injury action is typically a treating physician: the family physician or a treating specialist who was involved in the patient’s care at a critical moment.
Non-party experts are witnesses with relevant expertise who were not retained by a party but who provide opinion evidence based on their personal observations or examinations for purposes other than the litigation.
Westerhof establishes that a witness with special skill, knowledge, training, or experience who was not engaged by a party can give opinion evidence without complying with Rule 53.03 of the Rules of Civil Procedure where two conditions are met: the opinion is based on the witness’s observation of or participation in the events at issue, and the witness formed the opinion as part of the ordinary exercise of his or her skill, knowledge, training, and experience while observing or participating in those events.
The article’s practical guidance on participant experts is two-fold. The scope of a participant medical expert’s opinion is restricted to their clinical involvement with the patient. Counsel should not expect broad and general opinions from a treating physician on the key issues in dispute; the opinion evidence will largely be confined to what is in the clinical notes and records. Equally important, counsel should be cautious about over-relying on participant experts. Unlike litigation experts, who are willing participants in the lawsuit, participant experts have found themselves in the middle of a dispute they did not choose. Their performance as a witness may be unpredictable.
The qualification stage: Mohan and White Burgess
Before any expert is permitted to testify at trial, the expert must be qualified by the trial judge. The article identifies the two cases that every plaintiff-side practitioner needs to know.
R v Mohan, [1994] 2 SCR 9 sets out the four-part test for the admission of expert evidence: relevance, necessity in assisting the trier of fact, the absence of any exclusionary rule, and a properly qualified expert. The framework is now over thirty years old and has been refined and applied across thousands of subsequent decisions, but the four steps remain the analytical core.
White Burgess Langille Inman v Abbott and Haliburton Co., 2015 SCC 23, [2015] 2 SCR 182 addresses the threshold question of expert bias. The Supreme Court of Canada considered whether an expert should be excluded for bias because the proposed expert faced potential financial liability if her opinion was not accepted. The Court held that even clear financial gain or loss is not sufficient on its own to disqualify a witness for bias. But the Court was clear that expert witnesses owe a duty to the court to give fair, objective, and non-partisan opinion evidence, that they must be aware of this duty and able and willing to carry it out, and that if they do not meet this threshold requirement their evidence should not be admitted.
The practical implication is that most trial judges will take their gatekeeper role seriously and will entertain defence objections at qualification, even on grounds that ultimately do not succeed. Plaintiff-side counsel should prepare for those objections and should think carefully about how they intend to qualify their expert.
The article suggests that the qualification wording itself matters. The example given for a medical malpractice case is instructive: counsel might ask that the expert be qualified to provide opinion evidence “with respect to the standard of care of diagnosing and treating appendicitis in a community emergency department in Ontario in 2018.” The specificity is important. It identifies the substantive issue (standard of care), the medical question (diagnosing and treating appendicitis), the institutional setting (a community emergency department), the jurisdiction (Ontario), and the relevant time (2018). The narrower and more specific the proposed scope of qualification, the harder it is for defence counsel to argue the expert is unqualified for it.
Common defence strategies to exclude or restrict expert evidence
The article identifies three defence strategies that recur at trial.
The first is a qualification challenge. The defence may argue that the expert lacks experience in the precise subject matter of the action: a neurologist who cannot comment on general pain complaints, a specialist cardiologist who cannot comment on the standard of care of an emergency medicine physician attending to a potential cardiac patient, an expert whose practice was not in the same kind of hospital as the defendant, or who was not practising during the relevant period. The defence to this argument is built at the outset of the case in the choice of expert. The better the initial choice, the less force the qualification challenge will carry.
The second is a deficiency-of-report challenge. The defence will argue that the expert’s written report fails to disclose the reasoning behind the conclusion, that the report is conclusory, that the expert is impermissibly attempting to provide opinion evidence at trial on matters not adequately set out in the report under Rule 53.03. Peller v Ogilvie-Harris, 2018 ONSC 725, captures the controlling principle. While an expert is not bound by the four corners of the written report, and although a trial judge does not expect the expert to read from the report, the report must articulate expressly the opinion the expert has arrived at after a full review of the file and the literature, and it must set out the reasons supporting that opinion. The rule is not complied with if, after reading the statement of opinion, the court is left guessing about what the expert means. The practical guidance for plaintiff-side counsel is to review every expert report with the question in mind: is the expert’s reasoning visible on the page? If the report jumps from facts to conclusion without explaining the path, the defence will exploit the gap.
The third is a bias-of-participant-experts challenge. Treating physicians are, by definition, in a relationship with the patient-plaintiff that is not the relationship of a litigation expert. Defence counsel will argue that the relationship creates an inherent bias that should disqualify the treating physician from giving opinion evidence. The argument has generally been rejected. Doobay v Fu, 2020 ONSC 3329, frames the response directly: if treating physicians could never testify as experts in litigation involving their patients, which is the implication of the bias argument taken to its logical conclusion, then a treating physician who is often in the best position to provide the court with expert evidence could never do so. That is not the law. Stevenhaagen (Estate) v Kingston General Hospital, 2019 ONSC 6541 captures the same principle from the trial judge’s perspective: a treating physician’s potential preference for an outcome in which their own involvement caused no harm is not, on its own, a basis to exclude their evidence altogether, though it remains relevant to the weight the trial judge will ultimately give to that evidence.
The article does identify one nuance. In a medical malpractice case, if the participant expert’s own conduct could have contributed to the patient’s poor outcome, the bias argument may carry more force. The risk of exclusion or weight discounting increases when the participant expert has skin in the game.
The article’s central practical point
The article’s conclusion brings the three strands together. Expert evidence is the foundation of personal injury litigation, but the foundation is fragile if not protected. Counsel cannot assume that a well-written report will translate into persuasive testimony at trial. The right expert, with appropriate experience, who can withstand the scrutiny the defence will bring, is built into the case from the outset. The choice of expert at retainer, the review of the expert’s report before service, the preparation for the qualification motion, and the management of the defence’s expected challenges are all part of the same continuum of work.
Where to read
The article is available on the OTLA member portal in the archived Winter 2023/2024 edition of The Litigator. Paul’s published work in The Litigator and other professional journals is listed on his Media page.
Context
The article was published when Paul was a partner at Will Davidson LLP. Paul is now a partner at Davidson Cahill Morrison LLP. The DCM site continues to engage with the Rule 53.03 framework in its analysis of late-filed expert reports and related procedural issues. The doctrinal framework the article relies on, Westerhof on the types of experts, Mohan and White Burgess on qualification and bias, and the body of trial-level Ontario authority on report deficiencies and participant expert bias, has remained stable through to the date of this post. The article continues to be useful reference reading for plaintiff-side personal injury and medical malpractice practitioners in Ontario.
