Underscoring the importance of sound science in expert opinions, the United States Court of Appeals for the Seventh Circuit upheld the exclusion of expert testimony that did not adequately draw or extrapolate from reliable sources. C.W. v. Textron, Inc., No. 14-3448, 2015 WL 5023926 (7th Cir. Aug. 26, 2015).

The Plaintiffs were two parents who brought a toxic tort suit on behalf of their children against Defendant Textron, Inc. arising out of Textron’s fastener manufacturing operations in Rochester, Indiana. Plaintiffs claimed that Defendant’s release of vinyl chloride, a toxic gas, contaminated the drinking water in nearby private wells and, as a result, caused certain health problems experienced by Plaintiffs, as well as future risks of cancer and other health complications.

To show causation linking Plaintiffs’ ailments to a vinyl chloride release, Plaintiffs offered the testimony of three medical doctors who relied on differential etiology, a process-of-elimination approach that establishes causation by ruling out other possible causes.  They supported their conclusions in part by citing to studies of the harmful effects of vinyl chloride exposure in adults and animals, and relying on the medical history of the plaintiffs. The experts found no studies specifically evaluating the effect of vinyl chloride on children.

The district court excluded the experts’ testimony, finding the experts did not use reliable bases to support their opinions.  With no evidence of causation, the district court granted summary judgment for Defendant. 

On review, the Seventh Circuit first found that the district court properly followed the Daubert framework by exhaustively evaluating the reliability of the doctors’ opinions. The Court then affirmed the district court’s exercise of discretion to exclude the experts’ opinions because the experts failed to adequately “bridge the gap” between their causation conclusions and the studies they cited when conducting their differential etiology.