What is the general rule and exceptions to standard medical practice in medical malpractice?

The general rule and the exceptions were examined in the case of ter Neuzen v. Korn (1995), 1995 CanLII 72 (SCC), 11 B.C.L.R. (3d) 201 (S.C.C.), at p. 218: ... Courts and juries do not have the necessary expertise to assess technical matters relating to the diagnosis or treatment of patients. Where a common and accepted course of conduct is adopted based on the specialized and technical expertise of professionals, it is unsatisfactory for a finder of fact to conclude that such a standard was inherently negligent. On the other hand, matters falling within the ordinary common sense of juries can be judged to be negligent. For example, where there are obvious existing alternatives which any reasonable person would utilize in order to avoid a risk, one could conclude that the failure to adopt such measures is negligent notwithstanding that it is the prevailing practice among practitioners in that area. and at p. 220: ...as a general rule, where a procedure involves difficult or uncertain questions of medical treatment or complex, scientific or highly technical matters that are beyond the ordinary experience and understanding of a judge or jury, it will not be open to find a standard medical practice negligent.