Causation in Nova Scotia Personal Injury Claims – Kremer v. Walker
It is rare that a person injured in a car accident, medical malpractice claim, or some other accident doesn’t have some pre-existing health problems or conditions that may – or may not – play a part in the injuries that are the subject of litigation.
What Caused the Injuries?
A defendant will not be found liable (responsible) for a plaintiff’s injuries unless the plaintiff can prove that the defendant actually caused an injury to the plaintiff.
So defendant lawyers spend a great deal of time investigating whether the plaintiff ever had any pre-existing injuries or health problems that may be the cause of the plaintiff’s injuries.
“But For” Rule
The Supreme Court of Canada, in a case called Resurfice Corp. V. Hanke ruled that the appropriate test for the court to use when determining causation is the “but for” test. In other words, “but for” the defendants actions, would the plaintiff have been injured.
Like many rules, a number of exceptions have developed as various courts have considered the myriad different circumstances that can arise in complicated personal injury claims.
Justice Coady of the Supreme Court of Nova Scotia recently provided some clarity in his reasoning in Kremer v. Walker.
In his decision Justice Coady stated:
 The issue of causation in this action is complicated by a number of factors. Those factors include (1) various ongoing health problems, (2) pre-existing injuries from the 1990 truck accident, (3) the effects of long term obesity on Mr. Kremer’s body, (4) the second motor vehicle accident in 2007 and (5) the lack of professional medical evidence and (6) Mr. Kremer’s credibility.
 It is well established that a plaintiff bears the burden of establishing causation. In this case Mr. Kremer must satisfy the court that the July 21, 2007-accident caused injury. He must do so on a balance of probabilities.
 In Resurfice Corp. V. Hanke, 2007 SCC 7 (CanLII), 2007 SCC 7 the Supreme Court of Canada ruled that the “but for” test is the appropriate test for causation. McLaughlin, J. stated at paragraphs 20 through 25:
20 Much judicial and academic ink has been spilled over the proper test for causation in cases of negligence. It is neither necessary nor helpful to catalogue the various debates. It suffices at this juncture to simply assert the general principles that emerge from the cases.
21 First, the basic test for determining causation remains the “but for” test. This applies to multi-cause injuries. The plaintiff bears the burden of showing that “but for” the negligent act or omission of each defendant, the injury would not have occurred. Having done this, contributory negligence may be apportioned, as permitted by statute.
22 This fundamental rule has never been displaced and remains the primary test for causation in negligence actions. As stated in Athey v. Leonati, at para.14, per Major J., “[t]he general, but not conclusive, test for causation is the ‘but for’ test, which requires the plaintiff to show that the injury would not have occurred but for the negligence of the defendant.” Similarly, as I noted in Blackwater v. Plint, at para.78, “[t]he rules of causation consider generally whether ‘but for’ the defendant’s acts, the plaintiff’s damages would have been incurred on a balance of probabilities.”
23 The “but for” test recognizes that compensation for negligent conduct should only be made “where a substantial connection between the injury and the defendant’s conduct” is present. It ensures that a defendant will not be held liable for the plaintiff’s injuries where they “may very well be due to factors unconnected to the defendant and not the fault of anyone”: Snell v. Farrell, at p.327, per Sopinka J.
24 However, in special circumstances, the law has recognized exceptions to the basic “but for” test, and applied a “material contribution” test. Broadly speaking, the cases in which the “material contribution” test is properly applied involve two requirements.
25 First, it must be impossible for the plaintiff to prove that the defendant’s negligence caused the plaintiff’s injury using the “but for” test. The impossibility must be due to factors that are outside of the plaintiff’s control; for example, current limits of scientific knowledge. Second, it must be clear that the defendant breached a duty of care owed to the plaintiff, thereby exposing the plaintiff to unreasonable risk of injury, and the plaintiff must have suffered that form of injury. In other words, the plaintiff’s injury must fall within the ambit of the risk created by the defendant’s breach. In those exceptional cases where these two requirements are satisfied, liability may be imposed, even though the “but for” test is not satisfied, because it would offend basic notions of fairness and justice to deny liability by applying a “but for” approach.
 The Supreme Court commented on this decision in Fullowka v. Pinkerton’s of Canada Ltd., 2010 SCC 5 (CanLII), 2010 SCC 5 at paragraph 93:
I agree with the Court of Appeal that the trial judge applied the wrong legal test for causation. When he wrote his reasons in 2004, the trial judge did not have the advantage of this court’s judgment in Resurfice Corp. v. Hanke, 2007 SCC 7 (CanLII), 2007 SCC 7. That decision clarified the law of causation, holding that absent special circumstances, the plaintiff must establish on the balance of probabilities that the injury would not have occurred but for the negligence of the defendant: Hanke, at paras. 21-22; Athey v. Leonati, 1996 CanLII 183 (S.C.C.),  3 S.C.R. 458 at para.14.
 The “exceptional circumstances” approach was commented on at paragraph 95 of the Fullowka decision:
The appellants submit in the alternative that this case falls into the class of exceptional situations discussed in Hanke in which the test for causation should be relaxed to the “material contribution” standard. I cannot accept this submission. As Hanke made clear, the sorts of special situations for which the material contribution test is reserved generally have two characteristics. First, it is impossible for the plaintiff to prove that the defendant’s negligence caused the injury under the “but for” test, and second, it is clear that the defendant breached a duty of care owed to the plaintiff and thereby exposed the plaintiff to an unreasonable risk of injury of the type which the plaintiff ultimately suffered: Hanke, at para. 25.
 For these reasons this plaintiff must discharge his onus using the “but for” test. This case does not attract either exception.