Professionals who become involved as observers or participants in events giving rise to court actions are typically treated as “fact witnesses” in court proceedings. They give testimony concerning what transpired and provide relevant input used by a Court to make factual findings. In some cases, however, professionals may wish to provide opinion evidence to the Court by relying on their professional expertise. The ability to do this is limited, and very much depends on the nexus between the professional’s specific expertise, the opinion being rendered and the role of the professional in the facts of each case.
Qualifying the “participating expert”
A recent Ontario Divisional Court case examines and applies the test to be met for professionals involved in the facts of a case seeking to proffer expert opinions. In Rogelstad v. Middlesex Health Alliance, 2025 ONSC 263 (Rogelstad), Dr. Rogelstad, an ophthalmologist, had his hospital appointment suspended when he refused to comply with the hospital’s mandatory COVID-19 vaccination policy. He appealed unsuccessfully to the Health Professionals Review and Appeal Board (HPRAB). Dr. Rogelstad then appealed to the Ontario Divisional Court.
During the course of the appeal before the HPRAB, Dr. Rogelstad sought to have his submissions on COVID-19 vaccine safety and efficacy admitted as expert opinion, not through a formal qualification process but by arguing that he was a “participating expert” under the framework set out in Westerhof v. Gee Estate (Westerhof).[1]
The Court rejected this submission, holding that the test set out in Westerhof was not met. In Westerhof, the Court adopted the phrase “participating expert” referring to witnesses with relevant expertise and involved in the underlying facts of the case, and considered whether such witnesses needed to comply with rule 53.03 in order to proffer expert opinion evidence to the Court. Justice Simmonds concluded that a witness with special skill, knowledge, training or experience who has not been engaged by or on behalf of a party to the litigation may give opinion evidence for the truth of its contents without complying with rule 53.03 where:
1. The opinion to be given is based on the witness’ observation of or participation in the events at issue; and
2. The witness formed the opinion to be given as part of the ordinary exercise of his or her skill, knowledge, training and experience while observing or participating in such events.
The Divisional Court in Rogelstad upheld the HPARB decision that this test had not been met. Although Dr. Rogelstad was a physician and had held leadership roles at the hospital, including participation in pandemic planning committees, he had no training or expertise in public health, infectious diseases, vaccines, medical microbiology or infection prevention and control. The Court found that the opinions he sought to give—relating to public health, epidemiology and vaccine policy—fell outside his clinical expertise as an ophthalmologist.
Conclusion
A litigant’s professional status does not entitle them to bypass the rigorous standards of expert admissibility, particularly when offering contested scientific opinions outside their domain of specialization. Even in administrative proceedings governed by flexible evidentiary rules, tribunals must maintain the integrity of the expert evidence regime by relying on independent, properly qualified experts.
Participating experts must offer opinions derived from their direct involvement and within their specific area of expertise. It cannot be used as a backdoor for litigants to introduce scientific opinions without proper qualification.
For more information on this topic, please reach out to the author, David Elliott.
[1] Westerhof v Gee Estate, 2015 ONCA 206.
