Oregon Court of Appeals Clarifies Causation

By Rachel Perry


In Haas v. Estate of Carter, 316 Or App 75 (Dec. 1, 2021), the Oregon Court of Appeals affirmed the trial court’s refusal to give the “substantial factor” jury instruction in a motor vehicle case. The decision is significant for trial lawyers and their clients because it clarifies the causation standard for tort claims in Oregon. The court’s ruling and its potential impact on future cases is discussed below.


I. The Lawsuit


In Haas, the plaintiffs asked the Oregon Court of Appeals to find that negligence plaintiffs have a right to the substantial factor instruction in every negligence case. The plaintiff-appellants, Roberta and Kevin Haas, (“plaintiffs”) were injured when their vehicle was rear-ended by defendant-respondent Carter (“defendant”). Plaintiffs sued defendant for negligence and sought recovery for pain and medical treatment. There was a question as to whether plaintiffs’ medical treatment was necessitated by the accident or by their age and previous injuries.


The negligence question went to a jury trial and a dispute arose over the causation jury instructions. On appeal, plaintiffs asked the Court of Appeals to find that the “substantial factor” causation instruction “is appropriate in cases involving ‘multiple factors that were actual or potential causes of plaintiffs’ physical conditions,” not only those cases where multiple defendants are involved. Plaintiffs requested the court find that the substantial-factor instruction be given in every case where a preexisting condition has been aggravated, or a prior infirm condition makes the plaintiff more subject to injury. Plaintiffs contended that in all such cases, a prior infirmity is a causative factor that “requires the substantial-factor instruction to be given.”


II. The Court’s Ruling


The Court rejected plaintiff’s contention, holding that the substantial factor instruction is not appropriate in all negligence cases. In making its ruling, the Court clarified the purposes of the two causation instructions and explained that they exist to reflect different types of cases. The but-for causation is the standard for negligence actions; a plaintiff must ordinarily demonstrate that, “but-for the defendant’s negligence, the plaintiff would not have suffered harm.” In contrast, substantial factor causation is more appropriate in cases “involving multiple causes of a plaintiff’s injury” where it is “more useful to think of causation in terms of whether the defendant’s negligence contributed to the injury in an important or material way.”


The court drew a clear line between a “susceptibility,” or an increased likelihood of injury, and a “cause,” or an actual condition that actively contributes to an injury. This distinction has previously been drawn in workers’ compensation cases such as Corkum v. Bi-Mart Corp., 271 Ore. App. 411 (2015) and with this decision, the Court expanded the reasoning to apply to all negligence cases. The Court ruled that evidence of a “susceptibility” does not warrant use of the substantial factor instruction.


Judge James writes a strong concurrence attacking the Oregon court preference for the but-for instruction as Judge James considers the substantial factor instruction to be “the more elegant, accurate, and understandable way to instruct jurors.” Judge James opines that but-for causation is subsumed into substantial factor causation, and therefore substantial should be the preferred rule. While Oregon courts have carved out exceptions for when a but-for instruction is insufficient, there do not appear to be any cases where substantial factor has been held to be an inadequate instruction. James underscores that in any negligence action, a factfinder must properly consider the whole of circumstances to determine whether “any individual’s conduct is sufficiently substantial” for liability.


III. Analysis


Haas is a win for insurers and policyholders on most fronts. The court does expand the definition of “cause” to include “any cause” of an injury “whether or not that cause was the result of a negligent act,” but this change will likely not heavily affect application of the “but for” causation rule. In fact, the Haas opinion presents future plaintiffs with a hard line to demonstrate their underlying infirmities fit into the definition of a “cause.”


While the concurrence highlights issues with the distinction between susceptibility and cause, the majority’s reasoning existing case law that a substantial cause instruction [is only applicable in certain types of negligence matters and does not automatically apply to eggshell plaintiffs—plaintiffs with underlying conditions making them more fragile than the healthy plaintiff.


The Court leaves open a trail for future similar appeals that could have been brought here: for example, that some medical hardware implanted into plaintiff contributed to causing one of the injuries or cases where a plaintiff argues “a similar but not identical result would have followed without the defendant’s act.” The concurrence also raises the potential that future decisions may change if future plaintiffs with similar prior infirmities object to the use of the but-for instruction at all in their jury trial.

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