This is the sixth article of our series discussing practical and evidentiary issues in medical malpractice. Each article will examine recent medical malpractice case law and focus on the practical and evidentiary issues within them. The goal is to provide some useful insight into the obstacles that occurred in hopes that future cases can adapt and develop new ways to overcome these challenges.
Introduction
To succeed in a medical malpractice claim, the plaintiff must prove that there is a causal link between the negligent conduct of the health care provider and the plaintiff’s injuries. While it sounds straightforward, causation is often the most difficult and costly element to prove due to issues such as pre-existing injuries, divisibility of injuries, multiple tortious or non-tortious events, limitations of medical science and lack of direct evidence. Historically, the law on causation was a highly contentious issue. Over the last quarter century, the Supreme Court of Canada (SCC) has ruled several times on the causation issue, re-stating and clarifying the proof required for plaintiffs to succeed in a medical malpractice claim.
Snell v. Farrell (1990)
In order to understand the basis of the modern law on causation in medical malpractice cases, one must look back to Snell v. Farrell1 (“Snell”). In this case, the defendant ophthalmologist was surgically removing a cataract from the plaintiff’s eye. After injecting a local anaesthetic into the retrobulbar muscles behind the eyeball, the defendant noticed a small discolouration, which he stated was a very small retrobulbar bleed. On palpitating the eye, he found that it was not hard and there were no other signs of retrobulbar haemorrhage, and he continued the operation. Subsequently, the optic nerve atrophied, resulting in loss of sight.
One possible cause of atrophy is pressure due to retrobulbar haemorrhage. The experts were unable to state with certainty what caused the atrophy or when it occurred. The trial judge accepted the expert evidence that where there is bleeding other than the obvious pinprick of the needle, the operation should not be continued. Relying on the McGhee v. National Coal Board2 (“McGhee”) decision, the trial judge found that the plaintiff had prima facie proved causation, and the defendant was liable. The defendant’s appeal was dismissed.
When the SCC granted leave to appeal, the plaintiff’s bar hoped that the Court would adopt one or both of the options for proving causation outlined in McGhee. That is, causation can be proven simply by proving that the defendant’s negligence created a risk of harm and that the plaintiff’s injury fell within that risk – or alternatively, where the negligence created or increased the risk of harm, and the injury suffered fell within that increased risk, the burden of proof then shifts to the defendant to disprove causation.