On October 23, 2018, Paul hosted a webinar for the Ontario Trial Lawyers Association on how to find the right expert in a medical malpractice case. The session covered what medical experts look for from lawyers, insight into the working habits of frequently retained experts, the essential evidence required to prove a claim in medical malpractice, and practical advice on securing experts for consultation, reports, and trial testimony.
The topic remains central to plaintiff practice in Ontario. In all but a narrow set of cases, medical malpractice claims live or die on expert evidence.
Why expert evidence drives outcomes
The Supreme Court of Canada in ter Neuzen v Korn, [1995] 3 SCR 674, confirmed that the standard of care in medical negligence cases is generally established through expert evidence, with a limited exception for matters falling within ordinary common sense. Armstrong v Ward, 2021 SCC 1, more recently confirmed that framework. The same is largely true of causation, where mechanism and timing typically lie outside lay understanding and require an expert to explain how the breach produced the injury.
The practical consequence is that the choice of expert is not a procedural detail. It is a strategic decision that shapes every later step of the case: what facts the trial judge or jury hears, how those facts are framed, and whether the claim survives admissibility challenges before it is heard on the merits.
The admissibility framework
In Ontario, an expert opinion must clear the framework set out in R v Mohan, [1994] 2 SCR 9, and refined by the Supreme Court in White Burgess Langille Inman v Abbott and Haliburton Co., 2015 SCC 23. The court asks whether the evidence is relevant, necessary to assist the trier of fact, offered by a properly qualified expert, and not caught by an exclusionary rule. Beyond that threshold, the court conducts a discretionary gatekeeping inquiry that includes the expert’s independence and impartiality.
This is not theoretical. Defence counsel routinely test the qualifications and independence of plaintiff experts at trial, including by motion before testimony begins. An expert who looks strong on paper can still be excluded if the report reads as advocacy rather than independent opinion.
Compliance with Rule 53.03 of the Rules of Civil Procedure, including the Form 53 acknowledgment of the expert’s duty to the court, is the floor, not the ceiling. The substance of the report, the manner of its drafting, and the expert’s conduct in prior cases will all factor in.
Specialty match and small communities
The expert should ordinarily practise in the same specialty as the defendant, at a comparable level, in a comparable setting. A community emergency physician cannot easily speak to the standard expected of a specialist neurosurgeon, and a generalist commenting on a specialist procedure invites a successful qualification challenge.
Ontario specialty communities are also small. In sub-specialties such as paediatric cardiac surgery or maternal-fetal medicine, the pool of qualified experts who do not know the defendant or share a hospital affiliation can be limited. Out-of-province and international experts are common in those cases, which brings its own logistics around timing, travel, and trial scheduling.
The plaintiff and defence are not similarly resourced
Defendant physicians in Ontario are typically defended at the expense of the Canadian Medical Protective Association, which has the resources and institutional knowledge to retain leading experts repeatedly. Plaintiff firms fund expert costs out of their own working capital, often for years before trial.
That asymmetry is a structural feature of medical malpractice litigation in Ontario. It does not change the standard a plaintiff must meet. It does mean that plaintiff counsel cannot afford a misstep on expert selection.
What to look for
Beyond formal qualifications, the practical questions that tend to matter most:
Has the expert produced a clear written opinion before, or only verbal advice?
Does the expert teach, publish, or sit on professional bodies in the relevant area?
How has the expert performed under cross-examination in previous cases, and on what topics?
Can the expert explain complex medicine in language a juror can follow without losing precision?
Is the expert genuinely available for the timelines the case will require, including responding to defence reports and attending trial?
A consulting expert who is excellent on paper but cannot communicate to a jury becomes a liability at trial. A clear communicator without the academic standing to withstand qualification challenges is also a problem. The right expert is usually a combination of credibility on paper, clarity in communication, and disciplined adherence to the role of the independent expert.
Practical observations
The retention of the expert is one of the earliest meaningful decisions in any medical malpractice file. It is often made before discoveries are complete and sometimes before all records have been received. Building relationships with potential experts well in advance of any one case, understanding their availability and working style, and matching the expert to the specific medicine in issue all reduce the risk that the case is undone by an evidentiary problem that was foreseeable at the outset.
For the plaintiff side, the cost and difficulty of identifying the right expert are not a reason to avoid otherwise meritorious cases. They are a reason to do the work early, with the right people, and with a clear-eyed view of what the trial record will need to look like by the time the case reaches a courtroom.
