On February 12, 2020, the Oregon Court of Appeals expanded the admissibility of expert testimony regarding causation of a plaintiff’s personal injury in a case titled Miller v. Elisea. In Miller, plaintiff was involved in a minor car accident, and developed symptoms that were ultimately diagnosed as fibromyalgia.  Plaintiff sued, alleging that the car accident caused her fibromyalgia. At trial, plaintiff called two physicians to testify that the car accident caused her fibromyalgia. However, the trial court excluded the physicians’ testimony and held that there was no consensus in the medical community that a car accident could cause fibromyalgia.

The Court of Appeals reversed the trial court’s holding, stating that a lack of consensus in the medical community is not, by itself, a reason to disqualify expert testimony. Rather, expert testimony is admissible if the expert’s theory of causation is supported by other factors such as clinical experience, peer-reviewed literature, and studies. Ultimately, the court held that the plaintiff’s expert testimony regarding causation is admissible and it is up to the jury to give the testimony the weight they feel it deserves.

Miller expands on the Court of Appeals’ previous decision in Marcum v. Adventist Health System, which also expanded the scope of admissibility of novel medical theories of causation. Miller will likely encourage plaintiffs to acquire experts who rely on novel and less recognized theories of causation for medical diagnosis in order to create a nexus between the allegedly negligent action and the plaintiff’s injuries. The court’s inclination to allow into evidence testimony regarding novel and unrecognized theories of causation stray from the policy behind denying unrecognized theories of causation held in State v. O’Key: “Evidence perceived by lay jurors to be scientific in nature possesses an unusually high degree of persuasive power.  The function of the court is to ensure that persuasive appeal is legitimate.” However, as the Miller decision indicates, the court is entrusting jurors to decide themselves whether these novel theories of causation are legitimate or not.  As such, trial lawyers should expect that expert witnesses will be allowed to testify regarding medical causation of a plaintiff’s injuries, despite the theory of causation not being recognized by a consensus in the medical community.