What is the test for determining fault in a medical malpractice case?

The focus must not be on whether a specific act or omission of the practitioner constitutes fault but rather on whether the physician has met the required standard of care. In St. Jean v. Mercier, [2002] 1 S.C.R. 491, 2002 SCC 15, para. 53, Gonthier J. stated: . . . To ask, as the principal question in the general inquiry, whether a specific positive act or an instance of omission constitutes a fault is to collapse the inquiry and may confuse the issue. What must be asked is whether that act or omission would be acceptable behaviour for a reasonably prudent and diligent professional in the same circumstances. The erroneous approach runs the risk of focussing on the result rather than the means. Professionals have an obligation of means, not an obligation of result.

The physician is not obligated to guarantee the result nor is the physician (or nurse) bound to make no mistake. What the patient is entitled to is the exercise by the practitioner of reasonable skill, care and judgment. This is described by Rand J. in Wilson v. Swanson, 1956 CanLII 1 (SCC), [1956] S.C.R. 804 at 812: An error of judgment has long been distinguished from an act of unskilfulness or carelessness or due to lack of knowledge. Although universally-accepted procedures must be observed, they furnish little or no assistance in resolving such a predicament as faced the surgeon here. In such a situation a decision must be made without delay based on limited known and unknown factors; and the honest and intelligent exercise of judgment has long been recognized as satisfying the professional obligation.