Causation in medical malpractice cases.

Introduction

In any personal injury case, there are a number of elements that must be proven before the plaintiff can succeed. The standard in civil matters is a balance of probabilities test. This can be translated in percentage terms as 51%. To establish negligence, the plaintiff must prove that the defendant by a breach of his or her duty of care caused injury to the plaintiff.

The intent of this article is to address the issue of causation, particularly in the context of a medical malpractice lawsuit. It is this element, more than any other, which often causes the plaintiff to fail in what otherwise appears to be a good case.

The Law

It is absolutely essential for legal counsel to consider the issue of causation at the outset of any case. There is no point in spending countless hours and money only to conclude that even if the physician or surgeon breached his or her standard of care that it did not cause the injury complained of. Often the lawyer for the Canadian Medical Protective Association, the organization charged with defending medical doctors, will readily concede that the doctor was in breach but will argue that it made no difference in what happened to the plaintiff.

In recent years the Supreme Court of Canada has clarified the law of causation, both as it applies to personal injury law in general and medical malpractice in particular.

In the area of causation, like many others, Canadian courts have been heavily influenced by English law. As a result of the case of McGhee v. National Coal Board, 1973, a decision of the House of Lords, two theories of causation arose. The first was that the plaintiff need only prove that the defendant created a risk of harm and that the injury occurred within the area of risk. This had the effect of reversing the onus, thus requiring the defendant to show that the defendant's actions did not cause the harm. The second theory of causation was that, in these circumstances, an inference of causation was warranted in that there was no practical difference between materially contributing to the risk of harm and materially contributing to the harm itself.

Eleven years later, the House of Lords reconsidered the issue in Wilsher v. Essex Area Health Authority, 1988. The Court reaffirmed the principle that the burden of proving causation was on the plaintiff. The Court explained McGhee as promoting a robust and pragmatic approach to the facts to enable an inference of negligence to be drawn even though medical experts could not arrive at a definitive conclusion. The inference drawn was a matter of common sense.

Numerous Canadian cases decided after McGhee adopted either the reversal of onus or the inference interpretation, with no practical difference. When the latter approach was adopted and the creation of the risk by the defendant's breach of duty was deemed to have established a clear case, the onus was effectively shifted to the defendant.

The issue came before the Supreme Court of Canada in 1990 in the case of Snell v. Farrell. The appellant doctor, an ophthalmologist, performed cataract surgery on the then 70-year-old respondent's right eye. During surgery the doctor noticed what he thought was a very small retrobulbar bleed. After satisfying himself that there were no other signs of a haemorrhage, he proceeded with the operation. It was subsequently discovered that the optic nerve had atrophied and the respondent had no sight in her right eye.

Atrophy of the optic nerve results from the loss of the blood supply. One possible cause is a retrobulbar haemorrhage. The respondent's expert found evidence that she had suffered a stroke in the back of the eye. However, he could not identify what caused the stroke or when it occurred. Nor could the appellant's expert.

At trial, the judge accepted the evidence that where there is bleeding, other than the obvious pinprick of the needle, the operation should be aborted as it is impossible to determine the location of the bleeding. The trial judge was satisfied that the facts of the case brought it within the emerging branch of the law of causation whereby the onus to disprove causation shifted to the defendant. He concluded that the patient had clearly proved that the doctor's actions had caused her injury and the doctor had not satisfied the reverse onus.

The Supreme Court said that the traditional principle of tort law is that the plaintiff must prove on the balance of probabilities that, "but for" the tortious conduct of the defendant, the plaintiff would not have sustained the injury complained of. This approach, the Court acknowledged, was under attack due to the complexity of proof in some cases. The Court also acknowledged that in medical malpractice cases causation was often difficult to prove.

Mr. Justice Sopinka, for the unanimous Court, stated that if he were convinced that defendants, who had a substantial connection to the injury complained of, were escaping liability because the plaintiff could not prove causation under currently applied principles, he would not hesitate to adopt one of the alternatives arising out of McGhee. In doing so he also rejected the notion that McGhee, in fact, laid down a new principle. Rather by adopting a "robust and pragmatic approach to the undisputed primary facts of the case, the majority concluded that it was a legitimate inference of fact that the defenders' negligence had materially contributed to the pursuer's injury". Further, he said that the traditional principles of causation, properly applied, were adequate. He was concerned that adopting either theory would result in compensating plaintiffs without a substantial connection between the defendant's conduct and the injury. He said it was unfair to the defendant to find liability where an injury may very well be due to factors unconnected to the defendant and not the fault of anyone. He suggested that the medical malpractice crisis in the United States during the 1970s was due in part to the liberalization of the rules of recovery.

Mr. Justice Sopinka further expressed the view that dissatisfaction with the traditional approach stemmed in large part from too rigid an application by the courts. He stated: "Causation need not be determined by scientific precision." He adopted the view that causation was largely a question of fact, best answered by ordinary common sense. He said he was also of the view that both the burden and the standard of proof are flexible concepts.

In many malpractice cases, the facts lie particularly within the doctor's knowledge. In such cases, he said, the plaintiff will need to produce very little affirmative evidence to allow the court to draw an inference of causation in the absence of evidence to the contrary. However, it was not strictly accurate to speak of the burden shifting to the defendant. Rather, in certain cases the evidence adduced by the plaintiff will result in an adverse inference being drawn against the defendant. Whether an adverse inference is, in fact, drawn is a matter of the court weighing the evidence. The doctor runs the risk of an adverse inference being drawn in the absence of evidence to the contrary. His Lordship said this is sometimes called a provisional or tactical burden.

Mr. Justice Sopinka stated that the legal or the ultimate burden remains on the plaintiff. But in the absence of evidence to the contrary being adduced by the doctor, "an inference of causation may be drawn although positive or scientific proof of causation has not been adduced."

Of particular importance is that Mr. Justice Sopinka stated that it was not "essential that medical experts provide a firm opinion supporting the plaintiff's theory of causation. Medical experts ordinarily determine causation in terms of certainties whereas a lesser standard is demanded by the law." In other words, the law does not demand that the expert be 100% certain, only that he or she be at least 51% certain.

Turning to the facts of the case before them, Mr. Justice Sopinka said that the trial judge's finding that the doctor was negligent in continuing with the operation was fully supported by the evidence. It was common ground that the blindness occurred due to atrophy of the optic nerve which was occasioned by a stroke. There were two possible causes, one natural and the other due to continuing the operation.

The appellant, by negligently continuing with the operation, made it impossible to detect the bleeding which was alleged to have caused the injury. In such circumstances, it was open for the trial judge to draw an inference that the retrobulbar bleeding caused the injury. There was no evidence to rebut this inference. It was, therefore, open for the trial judge to find causation. It was not essential that the trial judge have a positive medical opinion to support a finding of causation. Thus, the Court dismissed the appeal.

The Supreme Court of Canada revisited the issue of causation in the decision of Athey v. Leonati, 1996, although this was a motor vehicle case. The Court affirmed that causation is established where the plaintiff proves on a balance of probabilities that the defendant caused or contributed to the injury. The general, but not conclusive, test for causation is the "but for" test, which requires the plaintiff to prove that the injury would not have occurred but for the negligence of the defendant. Where, however, the "but for" test is unworkable, the courts have recognized that causation is established where the defendant's negligence "materially contributed" to the occurrence of the injury. A contributing factor is material if it is more than trifling.

The Court made clear that it is not necessary to establish that the defendant's negligence was the sole cause of the injury. As long as the defendant partly caused the injury, then the defendant is liable, even though his or her act alone was not enough to create the injury. The defendant is liable for all injuries caused or contributed to by the defendant's negligence. If it were otherwise, then a plaintiff could recover 100% of his or her loss only when the defendant's negligence was the sole cause of the injuries.

Alberta Cases

A number of Alberta cases since Snell v. Farrell and Athey v. Leonati have addressed the causation issue.

Facts: The plaintiff brought a lawsuit against her doctor for failing to diagnose a condition known as reflex sympathetic dystrophy syndrome or alternatively, failing to refer the plaintiff to a specialist in a timely fashion.

Result: The trial judge found that the defendant was in breach of his duty for the latter. None of the experts could predict what the result would have been had there been a more timely referral. Nevertheless, there was a general consensus that the earlier specific treatment begins the better the prospect for recovery, and the trial judge drew an adverse inference of a causative link.

Facts: The physician failed to take adequate steps to rule out gestational diabetes. He further failed to use a new method for determining fetal size. The doctor estimated that the baby would be nine pounds at birth and not the 12 that he was. The plaintiff experienced a difficult delivery resulting in a difficult extraction of the posterior shoulder. The child was born and subsequently developed shoulder problems and problems with his balance.

Result: The physician was negligent in failing to assess the risk of gestational diabetes. At 36 weeks when it became apparent that the baby was larger than expected, the physician should have ordered an ultrasound test and considered the possibility of a caesarean section.

Facts: The plaintiff was an epileptic. He was seizure- free for some time and then began suffering nocturnal seizures although he also had a few during the day. He was prescribed dilantin and had no seizures for two years. The dosage was reduced. The defendant testified that his practice was to advise a patient that a reduction may result in seizures, but if the patient had a history of nocturnal seizures he would not caution the patient about driving. The plaintiff suffered a seizure watching television. The next day he was involved in a serious single vehicle collision.

Result: The physician was negligent for failing to warn the plaintiff about the risks of driving on the reduced dosage of dilantin. The trial judge concluded that if the plaintiff had been fully apprised he would not have agreed to the reduction or would not have driven alone.

Facts: A family physician treated the plaintiff for a urinary tract infection with Gentamicin. The known risks of Gentamicin included kidney damage and inner ear damage leading to an impairment of balance. After the patient underwent prostate surgery, another doctor prescribed Gentamicin. Upon discharge, the patient was unable to stand or walk. He was taken to the original physician's office and again prescribed Gentamicin. The plaintiff was diagnosed with Gentamicin ototoxicity by another doctor.

Results: The trial judge found that the administration of Gentamicin by the defendant during the third period was negligent. He found that it was not possible to determine which administration caused the plaintiff's condition. The effect of the successive treatments was cumulative. The administration of Gentamicin during the third period materially contributed to the plaintiff's condition. As it was not possible to apportion the injury between the three periods, the defendant was fully liable for the plaintiff's condition.

Conclusion

As a result of Snell v. Farrell and Athey v. Leonati decisions, the law of causation has been considerably clarified. The principles identified by those decisions are these:

* The burden of proof to prove the tortious acts of the defendant remains on the plaintiff throughout.

* The burden of proof, however, is flexible.

* The plaintiff must prove that the injury would not have occurred but for the negligence of the defendant.

* Where the "but for" test is unworkable then causation will be proven where the defendant's negligence materially contributed to the occurrence of the injury.

* The causation test is not to be determined by scientific precision. Rather it is essentially a question of common sense.

* The defendant's negligence need not be the sole cause of the injury. It is sufficient if the defendant's negligence was a cause of the harm.

7. Apportionment between tortious and non-tortious causes is not permissible. To do so would allow a defendant to escape liability even though the defendant caused or contributed to the plaintiff's entire injury.

8. The defendant is liable for the injury he or she caused.

It is essential that plaintiff's counsel consider causation issues early in the development of the case and retain causation experts early as well. Failure to do so may result in an excellent case on breach of care and damages, but with no basis for showing that the defendant caused the loss.