How is causation determined in medical negligence cases?

Causation is proved on the balance of probabilities. There are two aspects of the causation inquiry: cause in law which comprises the traditional remoteness inquiry and cause in fact. To be held liable in medical negligence the result must have been reasonably foreseeable. The court must be careful to place itself in the position of the person charged with the duty and to consider what he or she should have reasonably anticipated as a natural and probably consequence of neglect, and not give undue weight to the fact that a distressing accident has happened. Cardin v. Montreal, (1961) 1961 CanLII 77 (SCC), 29 D.L.R. (2d) 492 (S.C.C.).