Treating Physicians and Expert Testimony: Western District Reverses Verdict Over Undisclosed Causation Opinion

The Western District Court of Appeals recently reversed a defense verdict in a FELA wrongful death case, highlighting the critical boundary between a treating physician’s factual testimony and impermissible expert opinions on causation when such opinions are not properly disclosed during discovery.

In Ralls v. Soo Line Railroad (WD 86617), Plaintiff Shirley Ralls brought suit under the Federal Employers’ Liability Act, alleging her late husband developed lung cancer as a result of his exposure to carcinogens during his employment with Soo Line Railroad. Although both sides acknowledged that the decedent’s long history of tobacco use played a role in his cancer, the central issue at trial was whether occupational exposure to known carcinogens also contributed to his illness.

The pivotal testimony came from the decedent’s treating radiation oncologist. While not identified as an expert witness by either party, the treating physician gave sharply different testimony at two depositions. In his initial discovery deposition, the physician offered no definitive opinion on causation, citing incomplete records. In a second deposition taken to preserve his trial testimony, however, he testified unequivocally that smoking was the sole cause of the decedent’s cancer—an opinion based on additional materials he reviewed after his treatment of decedent had ended. Plaintiff objected to allowing treating physician’s trial testimony, arguing she had been unfairly surprised by his new opinion and had not been given an opportunity to rebut it. The trial court overruled her objections and denied her motion for a new trial after the jury returned a defense verdict.

The appellate court reversed.

In its opinion, the Western District emphasized long-standing principles governing the role of treating physicians as witnesses. Although treating physicians are typically fact witnesses, they may give expert opinions—even on causation— but only  to the extent such opinions are based on facts learned during the course of care and treatment. Once a treating physician reviews additional materials or formulates new opinions in preparation for litigation, those opinions fall under Missouri’s expert witness discovery rules and disclosure requirements. These requirements include a party’s obligation to disclose new information to the opposing party when the expert later changes his/her opinion before trial or bases the opinion on new or different facts from previously disclosed in deposition.

The Court found that the treating physician’s trial testimony relied on external research conducted after his treatment of the decedent had ended and offered new, definitive opinions not disclosed during the discovery deposition. Because these opinions went directly to the core issue at trial—whether workplace exposure played  any role in causing the cancer—the court concluded that the plaintiff had been unfairly prejudiced.

Notably, the FELA standard requires only that employer negligence “played any part, even the slightest,” in producing an injury or death. As such, excluding the surprise causation testimony could have materially affected the jury’s decision.

This decision serves as a clear reminder: if a treating physician will offer opinions on causation that go beyond the treatment record, the treating physician must be disclosed in advance as an expert witness—whether retained or non-retained—and any material change in the treating physician’s opinion must be communicated to the opposing party. Failure to do so may result in the exclusion of testimony or, as in this case, a reversal on appeal.