Which Doctor's Opinion Counts On Threshold Issues? Case Study: Sanson v Paterson v Sanson v Security National Insurance

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