Failure to Extrapolate! Seventh Circuit Requires Experts Connect Data with Opinions

On appeal, the Seventh Circuit resolved the questions of whether the district court abused its discretion in excluding the experts’ testimony based on the unreliability of their methodology and, if no abuse of discretion, whether summary judgment should be affirmed. The plaintiffs offered the testimony of three experts: (1) Dr. James Dahlgren, (2) Dr. Vera Byers, and (3) Dr. Jill Ryer-Powder. All three employed a “differential etiology” approach to causation and opined that vinyl chloride can and did cause the children’s illnesses. Dr. Dahlgren concluded that it was highly likely that the children would develop cancer in the future and that the levels of vinyl chloride in the plaintiffs’ water supply exceeded levels established by both federal (Environmental Protection Agency) and state regulators. Dr. Byers concluded that vinyl chloride can and did cause the children’s illnesses and linked the children’s gastrointestinal and immune system problems to their exposure. Based on timing, Dr. Byers also concluded that the children’s symptoms were most serious during exposure and subsided when the exposure ceased. Dr. Ryer-Powder found that the children’s exposure was at sufficient levels to cause harm and that such exposure was sufficient to present a risk of cancer in the future. Like Dr. Dahlgren, Dr. Ryer-Powder relied on exposures above regulatory standards in formulating her opinion, specifically excessive levels of vinyl chloride in drinking water. In her opinion, exposure above regulatory minimums placed vinyl chloride within the realm of possible causes for the children’s injuries.

Upon review, the Seventh Circuit stressed the district court’s role as the “gatekeeper” of expert testimony. The key to the gate was not the whether the expert’s opinion is correct, but the soundness and care behind the formulation of the opinion. C.W., 2015 WL 5023926, at *5.The court noted that in some cases, it is appropriate to determine whether there is too great an analytical gap between the data reviewed and opinion proffered. Thus, the court found that the district court properly adhered to the Daubert framework by outlining its principles, acknowledging the need for flexibility, and conducting in-depth reviews of the studies relied on by the experts. One study showed no significant increase in tumors developed by rats that were fed less vinyl chloride than the children were exposed to over a longer period of time. However, Dr. Ryer-Powder concluded that the study demonstrated that the children were at an increased risk for developing cancer. This was an inferential leap the district court was unwilling to make. Id. at *6. Furthermore, the district court rejected another study in which groups of adults were exposed to vinyl chloride at much higher levels and over a much longer period of time. Nevertheless, Dr. Byers relied on that study in concluding that the children were at an increased risk for developing cancer. In reviewing the district court’s rejection of those studies, the Seventh Circuit reasoned that the district court properly exercised its role as the gatekeeper under Daubert while acknowledging that the studies need not be precisely analogous to meet the reliability test. Id. at *6–7.

Similarly, the court of appeals examined the district court’s exclusion of the experts’ testimony. The court shared the district court’s concern regarding the experts’ failure to connect the dots from the studies to the illnesses and acknowledged the Supreme Court’s holding of General Electric v. Joiner, 522 U.S. 136 (1997). The court held that a district court’s exclusion of expert testimony resulting from too great an analytical gap between the data and the opinions, making the opinions nothing more than the ipse dixit of the expert, is not abuse of discretion. C.W., 2015 WL 5023926, at *7–8. Conversely, the plaintiffs asserted that there were no studies available on the impact of vinyl chloride on children because of the ethical and moral concerns regarding introducing toxins to children. However, the court pointed out that scientists have developed computer-based models to extrapolate from animal data to two human subjects and from high doses to lower doses. Such a method of extrapolation had even been recognized by the Environmental Protection Agency as a valid approach to bridging the gap between the studies and the general public.

The district court had also rejected the experts’ differential etiology because it found that methodology not reliable. The court of appeals agreed. It characterized Dr. Dahlgren’s approach as not scientific because it relied solely on his faith in his fellow physicians to previously detect alternative causes of the children’s symptoms.The court also affirmed the exclusion of Dr. Byers’s etiology because it failed to include the benefit of analogous studies and an acceptable method of extrapolation, forcing Dr. Byers, like the others, into a leap of faith concerning her determination that vinyl chloride had the capacities to cause injuries and provide the risk of injury. Id. The court also affirmed rejection of Dr. Ryer-Powder’s methodology because exceeding government regulatory exposure standards cannot alone prove causation. Id. at *8. To the extent the plaintiffs’ experts also relied on a temporal relationship between exposure and the children’s injuries, the district court also properly excluded this methodology. The Seventh Circuit had previously ruled in Ervin v. Johnson & Johnson, 492 F.3d 901, 904–5 (7th Cir. 2007), that a temporal relationship between an occurrence and symptoms is insufficient to prove causation. Although affirming the district court’s dismissal of the case due to absence of expert testimony, the court rejected the district court’s absolute exclusion of differential etiology as a method to establish general causation and adopted the Second Circuit’s view holding that it may be an appropriate method of proof in some cases. C.W., 2015 WL 5023926, at *9(“there may be a case…”).

The Seventh Circuit’s ruling in C.W. is significant because it demonstrates that, in toxic-tort matters, experts may be held to a standard more rigorous than what may be allowable under the general Daubert framework in another type of case. The court articulated that in some (i.e., not all) cases, it may be appropriate to examine the significance of the analytical gap between the data and the opinions offered. Unfortunately, the opinion offered no guidance as to particular claims or methodologies that might warrant such an examination. Moreover, the court further implied that it was not impressed by the experts’ failure to stay abreast of the latest technological advances that may have helped bridge the apparent gap. The court specifically referenced a computer model that could have extrapolated the data relied on by the experts. Id. at *8. The use and results of such a model certainly could have influenced the court’s decision.

Keywords: mass torts litigation, differential etiology, expert opinion, Daubert, vinyl chloride, extrapolation

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