What is the test for determining whether a surgeon is qualified to operate on a patient?

The test is also stated in Wilson v. Swanson, 1956 CanLII 1 (SCC), [1956] S.C.R. 804 at 811-812, 5 D.L.R. (2d) 113, by Rand J.: … What the surgeon by his ordinary engagement undertakes with the patient is that he possesses the skill, knowledge and judgment of the generality or average of the special group or class of technicians to which he belongs and will faithfully exercise them. In a given situation some may differ from others in that exercise, depending on the significance they attribute to the different factors in light of their own experience. The dynamics of the human body of each individual are themselves individual and there are lines of doubt and uncertainty at which a clear course of action may be precluded. There is here only the question of judgment; what of that? That test can be no more than this: was the decision the result of the exercise of surgical intelligence professed? Or was what was done such that, disregarding it may be the exceptional case or individual, in all the circumstances, at least the preponderant opinion of the group would have been against it? If a substantial opinion confirms it, there in no breach or failure …

This principle was affirmed in ter Neuzen v. Korn, 1995 CanLII 72 (SCC), [1995] 3 S.C.R. 674 at para. 33, 127 B.C.L.R. (4th) 577 where McLachlin J. (as she then was) said this: It is well settled that physicians have a duty to conduct their practice in accordance with the conduct of a prudent and diligent doctor in the same circumstances. In the case of a specialist, such as a gynaecologist and obstetrician, the doctor’s behaviour must be assessed in light of the conduct of other ordinary specialists, who possess a reasonable level of knowledge, competence and skill expected of professionals in Canada, in that field. A specialist, such as the respondent, who holds himself out as possessing a special degree of skill and knowledge, must exercise the degree of skill of an average specialist in his field. [citations omitted].