Justice Stinson’s Endorsement in Brown v. Wahl is a succinct and well-reasoned example of a discovery analysis in a medical malpractice claim where the injury is obvious and the issue is when the plaintiff ought to have inferred a potential claim against the defendant practitioners.
The defendant dentists moved for summary judgment based on a limitations defence. The limitations issue wasn’t the plaintiff’s knowledge of her injury. She encountered problems with her dentures immediately after one of the defendants constructed and inserted them. She knew, or ought to have known, that something was wrong with her dental work at that time.
The issue was when she should have known why she was experiencing the problems. Justice Stinson found that she ought to have inferred that she had a potential claim against the defendants once a third dentist, Dr. Singh, explained the source of the problems and advised her that he would have performed the procedure differently. No expert report was necessary.
 In my view, armed with the foregoing knowledge and information, a reasonably prudent person in the position of the plaintiff would have inferred that either or both of the defendants Casciato and Wahl had been negligent. She knew that the problem she was experiencing flowed from their treatment. She had to know that the outcome was substandard. Based on what she was told by Dr. Singh on December 13, 2011, she should have known that her problem “must have been caused through some act or failure to act by one or more of the professionals involved in the procedure and there was the likelihood of negligence of some kind, either in what was done or what was not done but should have been.” See McSween v. Louis, (2000) 2000 CanLII 5744 (ON CA), 132 O.A.C. 304, 187 D.L.R. (4th) 446 (ON C.A.) at paragraph 47.
 Here, based upon what she was told by Dr. Singh, the plaintiff ought to have known that the problems she was experiencing were caused by substandard treatment by one or both of the defendants. While she may have learned additional information about that substandard treatment once she received the expert reports in early 2014, in my view, those reports do not detract from the fact that she had sufficient knowledge to be aware of a breach by December 13, 2011 at the latest. Put another way, I find that the claims were discoverable by that date.
 This is not a case in which an expert opinion was necessary for the plaintiff to conclude that there was the likelihood of negligence of some kind. As the cases mentioned above make plain, it is enough for the plaintiff to have prima facie grounds to infer that the defendants caused harm, and certainty of the defendants’ responsibility for the act or omission that caused the loss is not a requirement for the limitation period to begin to run.
Readers may find it helpful to bookmark the Endorsement for its statement of the basic principles of a section 5 discovery analysis (paragraphs 13 – 20). The Endorsement quotes Justice Perell’s thorough discussion of discoverability in 2013’s Tender Choice Foods v. Versacold Logistics Canada Inc., a decision which I expect will remain the best summary of section 5 jurisprudence for some time.
Update: Compare Brown with another recent medical malpractice decision involving dentists, Maurice v. Alles et al.