What types of physicians can opine on threshold issues? In the Ontario Superior Court decision, Sanson v Paterson v Sanson v Security National Insurance, Justice W.D Black answers the type of physicians that qualify under section 4.3(3) of O. Reg 461/96.¹

He held that family physicians could be relied on for threshold determination but only on a case-by-case basis. Where they are involved in the plaintiff's care from the beginning, their opinion may be more valuable than a third-party expert previously unknown to the plaintiff.

The action arose from a motor vehicle accident where the defendant collided with the plaintiff, who was riding a bicycle. A central issue at trial was whether the mild traumatic brain injury the plaintiff asserted she suffered met the statutory threshold of a “permanent serious impairment of an important physical, mental, or psychological function.”² The plaintiff called four experts: two neuropsychologists and two family physicians, one of which was the plaintiff's own.

The defendants argued that under 4.3(3) of the regulation, the neuropsychologists did not qualify as physicians, and the family doctors did not have the requisite expertise. The defendants further argued that a Rule 53 report was required from a qualifying physician to establish threshold impairment. As the neuropsychologists had been proffered as litigation experts, their disqualification invalidated their report.

Justice W.D Black agreed in part with the strict interpretation of 4.3(3) that only “physicians” could give a medical opinion under that clause. He accepted that neuropsychologists were not properly physicians and could only provide corroborative evidence. However, he rejected that family physicians are not qualified to provide an opinion on the threshold. Although their qualifications must be assessed on a case-by-case basis, their experience may qualify them in some situations. For instance, one of the family physicians, Dr. Lay, had spent forty years of her career focusing on brain injuries and was renowned in her field. Additionally, a family doctor involved in the plaintiff's care from the outset of the accident may be better situated than a qualified expert who has met the plaintiff once to opine on the impact of the injuries.

Justice W.D. Black ultimately accepted Dr. Lay's opinion on the threshold issue because of her extensive expertise in brain injuries. He also held that fact witnesses like Dr. Lay could provide a determinative opinion on the threshold without tendering a Rule 53 report. Thus, reinforcing that expert reports are not required to establish threshold impairment.

1. 2022 ONSC 2972 (CanLII) | Sanson v. Paterson | CanLII
2. Insurance Act, RSO 1990, I 8, s 267.5(3,5).