Haas v. Estate of Mark Steven Carter

The but-for standard of causation is appropriate in multiple causation negligence cases, unless two causes concur to bring about an injury and either one of them, operating alone, would have caused the same result.

Haas appealed a jury verdict finding Carter not liable for negligence. Haas assigned error to the trial court’s refusal to instruct the jury on substantial factor causation. The Court of Appeals affirmed, holding Haas was not entitled to a substantial factor instruction because there was no evidence of multiple potential causes. Haas sought review by the Supreme Court, arguing that the substantial factor instruction is appropriate “whenever multiple factors may have contributed to a plaintiff’s injuries.” In response, Carter argued that but-for causation adequately describes the necessary causal connection in multiple cause cases, except when multiple causes act concurrently.The but-for standard of causation is appropriate in multiple causation negligence cases, unless two causes concur to bring about an injury and either one of them, operating alone, would have caused the same result. The Court found that a but-for instruction accurately describes the necessary cause-in-fact relationship in most negligence cases, even when multiple causes are involved. It reasoned that the instruction informs the jury that the causation element is met whenever the plaintiff’s injuries would not have occurred without the defendant’s actions and that remains true even if multiple acts contributed to the injuries. The Court also noted that the but-for standard does not require the jury to decide whether the defendant’s conduct was the sole or predominate cause. The Court held that Haas would not be entitled to a substantial factor instruction simply because Haas’ preexisting conditions could have caused the injuries. Affirmed.