Causation in medical malpractice

Today's decision of the Court of Appeal in the sad case of Fisher v. Victoria Hospital, 2008 ONCA 759 provides a useful summary of the law regarding causation in a medical malpractice case:

i) The Law of Causation

[53] Causation is an expression of the relationship that must be found to exist between the tortious act of the wrongdoer and the injury to the victim in order to justify compensation of the latter out of the pocket of the former: Snell v. Farrell, [1990] 2 S.C.R. 311, at p. 326. The primary test for establishing causation in negligence cases is the "but for" test. This was recently affirmed by the Supreme Court of Canada in Resurfice Corp. v. Hanke, [2007] 1 S.C.R. 333. The plaintiff must establish that "but for" the negligent act or omission of the defendant, the injury would not have occurred: see Athey v. Leonati, [1996] 3 S.C.R. 458, at para. 14. In special circumstances, the court may apply the "material contribution test". However, the circumstances where this test can be applied are limited: Hanke, at paras. 24 and 25. [14]

[54] Whatever test for causation is applied, it is clear that scientific precision is not required to support a finding of causation: Snell, at p. 328; see also: Aristorenas v. Comcare Health Services (2006), 83 O.R. (3d) 282 ( C.A. ). Accordingly, in medical malpractice cases, an expert capable of providing a firm opinion that supports the plaintiff's theory of causation is not required: Snell, at p. 330. Rather, the trial judge is entitled to consider all the facts and circumstances established by the evidence at trial, and, where appropriate, to draw an inference of causation through the application of reason and common sense. This approach has been termed "the robust and pragmatic approach": The legal or ultimate burden remains with the plaintiff, but in the absence of evidence to the contrary adduced by the defendant, an inference of causation may be drawn although positive or scientific proof has not been adduced. If some evidence to the contrary is adduced by the defendant, the trial judge is entitled to take account of Lord Mansfield's famous precept.[15] This is, I believe, what Lord Bridge had in mind in Wilsher when he referred to a "robust and pragmatic approach to the … facts: Snell, at p. 330; see also Aristorenas.

[55] Further, at p. 331 of Snell, Sopinka J. made the following comments concerning the differing roles of the trier of fact and expert witnesses: The respective functions of the trier of fact and the expert witness are distinguished by Brennan J. of the United States Supreme Court in the following passage in Sentilles v. Inter-Caribbean Shipping Corp., 361 U.S. 107 (1959) at pp. 109-10: The jury's power to draw the inference that the aggravation of petitioner's tubercular condition, evident so shortly after the accident, was in fact caused by that accident, was not impaired by the failure of any medical witness to testify that it was in fact the cause. Neither can it be impaired by the lack of medical unanimity as to the respective likelihood of the potential causes of the aggravation, or by the fact that other potential causes of the aggravation existed and were not conclusively negated by the proofs. The matter does not turn on the use of a particular form of words by the physicians in giving their testimony. The members of the jury, not the medical witnesses, were sworn to make a legal determination of the question of causation. They were entitled to take all the circumstances, including the medical testimony, into consideration.

[56] However, as indicated in the quotation from Snell at paragraph 54 above, the robust and pragmatic approach does not shift the burden of proof away from the plaintiffs. Rather, the plaintiff must still "provide an evidentiary foundation for finding that there is a substantial connection between the injury and the defendant's conduct": Barker v. Montfort Hospital (2007), 278 D.L.R. (4th) 215, at para. 54.

[57] Further, as this court emphasized at paras. 54 and 60 of Aristorenas, the robust and pragmatic approach offers a method for evaluating evidence. It is not a substitute for evidence that the defendant's negligence caused the plaintiff's injury; nor does it change the amount of proof required to establish causation.

[58] Finally, just as the robust and pragmatic approach cannot be used as a substitute for evidence, it cannot be used as a substitute for reviewing and making findings about relevant evidence.

[59] Put another way, the robust and pragmatic approach does not permit drawing inferences concerning either the ultimate issue of causation or links in the chain of causation without reviewing the relevant evidence and without making findings about the range of available inferences. As Rouleau J.A. pointed out at para. 63 of Aristorenas, quoting from Fairchild v. Glenhaven Funeral Services, [2002] 3 All E.R. 305 (H.L.), at para. 150, common sense cannot become a substitute for resort to the evidence: [E]ven though it is always for the judge rather than for the expert witness to determine matters of fact, the judge must do so on the basis of the evidence, including the expert evidence. The mere application of "common sense" cannot conjure up a proper basis for inferring that an injury must have been caused in one way rather than another.