Appeal Watch: Ediger Appeal to Revisit Causation Analysis
Causation is often the most difficult element to prove in a negligence action. The but for test, most famously articulated by Athey v Leonati,  3 SCR 458, helps to ensure fairness by requiring the plaintiff to prove on a balance of probabilities that “the injury would not have occurred but for the negligence of the defendant.” However, as with most aspects of law, there are also exceptions when it comes to proving causation.
The Supreme Court of Canada (SCC) will revisit the matter of causation when it hears Cassidy Alexis Ediger v William G. Johnston, 2011 BCCA 253, which was recently granted leave to appeal. Ediger is a medical malpractice case involving a young girl who suffered serious brain damage at birth after a failed “mid-level rotational forceps delivery.” At trial, Ediger, represented by her guardian, claimed that the appellant doctor’s negligence during the procedure caused her injuries and that he breached the standard of care by failing to obtain informed consent from the mother. The trial judge found the doctor liable and awarded damages to the respondent.
Dr. Johnson admitted that he breached the standard of care, but appealed the decision on the matter of causation. The British Columbia Court of Appeal, determined that because causation is a matter of fact, Dr. Johnson was required to prove that the trial judge made a “material error” on the matter of causation. It then considered two competing theories arising from the but for test. The more stringent theory holds that the defendant’s action must fall “within the ambit of risk.” A less onerous theory, also known as the “material contribution test,” was articulated in McGhee v National Coal Board,  ALL ER 1008, 1 WLR 1 (HL).This theory suggested that “causation was established if the defendant’s negligent act merely created a risk of harm.” The stricter theory was adopted by the SCC in Snell v Farrell,  2 SCR 311, and more recently confirmed in Resurfice Corp v Hanke, 2007 SCC 7.
The appellate court found the material contribution test to be inapplicable on the facts of this case “because it was not impossible for the respondent to prove that the appellant’s negligent conduct caused Cassidy’s injuries.” Thus, the respondent was required to prove on a balance of probabilities that there was a “substantial connection” between the risk of harm created by the doctor’s negligence and the resulting injuries. In reviewing the matter of causation, the court considered whether the doctor’s attempted forceps delivery had in fact caused the harm suffered by the respondent. On this matter, the trial judge had found that although the exact cause of the injury remained unknown, “the temporal connection between the procedure and [the resulting harm] was sufficient to reasonably infer that a causal connection existed between the two events.”
To determine whether it was appropriate for the trial judge to draw such an inference, the appeal judge referred to the approach in Snell, which permits an inference of causation to be drawn in circumstances where there is no evidence to the contrary on a plaintiff’s theory of causation. In this case, however, the appellant doctor had provided evidence that supported other explanations for the respondent’s harm. As a result, the appeal court found that the trial judge had erred in permitting an inference of causation to be drawn and allowed the appeal.
Just as the mens rea requirement in criminal law ensures only those accused with a proven guilty mind are convicted, the element of causation in tort law ensures that only those defendants who actually caused the plaintiff’s harm are found liable. As was most famously articulated in Donoghue v Stevenson,  All ER Rep 1, individuals owe a duty of care to avoid acts that might reasonably injure their neighbour. The element of reasonableness expressed by the neighbour principle suggests that a degree of fault is required on the part of the defendant.
While the tort system aims to deter individuals from engaging in behaviour that carries a risk of harm to others, it also carries the risk of potential plaintiffs seeking compensation for harms that fall outside the scope of reasonableness. By setting a high threshold for causation, the but for test protects against frivolous claims and helps to ensure the integrity of the tort system. The Snell relaxation ensures fairness to the plaintiff in circumstances where the but for test would otherwise be unworkable. But at the same time, the high threshold required to trigger it also provides the defendant with the opportunity to bring forward evidence to the contrary. In deciding whether a further relaxation to the but for test is appropriate, the SCC will be required to consider the interests of both parties.