In Shallow v. Follwell, the Missouri Court of Appeals for the Eastern District of Missouri reversed and remanded a jury’s verdict for defendant Dr. Follwell, holding the trial court improperly allowed cumulative expert witness testimony that imperiled the jury’s ability to fairly consider the quality and quantity of expert witness opinions.

The case involved a surgical mesh procedure to repair decedent’s hernia. After the doctor twice within 24 hours discharged the patient from the hospital, she returned to the hospital a third time, where she was diagnosed with a severe infection in her abdominal cavity, caused by leakage of toxic and infectious bowel contents into her abdomen. She died soon thereafter.

At trial, Dr. Follwell – designated as a fact and expert witness on his own behalf – did not dispute that decedent’s bowel was perforated, leaked, and caused the septic condition that led to her death. He denied that he caused the hole in her bowel, however, and presented his alternative theory that decedent suffered from undiagnosed atrial fibrillation, which caused a blood clot to form, restricted the blood flow to that section of decedent’s bowel, and ultimately weakened and perforated the bowel wall. Four other retained experts testified for Dr. Follwell: (1) a critical care specialist; (2) a cardiologist and internist; (3) a vascular surgeon; and (4) a colorectal surgeon.

While there is no “bright line” rule as to how many expert witnesses a party may utilize to prove or defend its case, Missouri trial courts are charged with admitting evidence that is both logically and legally relevant. The concept of legal relevance includes whether the evidence may, among other things, pose a danger of unfair prejudice, be a waste of time, and amount to the needless presentation of cumulative evidence. Missouri courts have expressed concern that excessive cumulative evidence risks invading the jury’s ability to resolve the case on the merits and evaluate the quality and credibility of expert opinions. Cumulative expert opinions may instead result in the jury simply “counting heads.” The Shallow v. Follwell court held that the trial court abused its discretion in failing to properly determine when cumulative evidence should stop.

It was not just the number of defendant’s experts that caused the Court of Appeals to reach its conclusion. Rejecting the defendant’s claim that each expert’s testimony was limited to his own area of medical expertise - cardiology, internal medicine, critical care, the vascular system, and the gastrointestinal system - the Court of Appeals ruled that what actually happened was that each expert presented his expert opinion in his own area of expertise, but also repeated the sum and substance of the defense’s alternative theory of causation, in testimony that extended beyond the expert’s specialty. The jury therefore heard the same opinions multiple times – essentially a “chorus of the same ultimate opinions” – which impeded its duty and ability to fairly weigh the evidence on each side.

In returning the case to the Circuit Court for a new trial, the Court of Appeals chastised the trial court for “ignoring its duty to properly assess whether the testimony was needed,” and reminded the trial court “to adhere to the principles and standards set forth in this opinion and elsewhere in Missouri law for determining the admissibility of cumulative evidence.”