In a decision with important implications for the admission of expert testimony in cases involving rare diseases, the Supreme Court of the United States declined to review a decision of the 9th Circuit which reversed a trial court’s decision barring plaintiff’s experts from testifying about the cause of plaintiff’s cancer. Wendell v. GlaxoSmithKline, 838 F. 3d 1227 (9th Cir. 2017), cert. den. ___ S.Ct. ___ (2018).
In 2007, at the age of 21 and after years of taking a combination of drugs to treat his ulcerative colitis, Maxx Wendell developed a rare and deadly form of lymphoma called hepatosplenic T-cell lymphoma. In the years leading up to his diagnosis these drugs had increasingly been associated with this form of lymphoma particularly in young males with ulcerative colitis, although it’s exceeding rarity made it nearly impossible to specifically quantify the risk through epidemiologic studies. While the background risk for this cancer (which had only first been identified in 1994 with only 200 or so cases reported in the medical literature worldwide from the 1990’s until the mid-2000’s) was understood to be approximately 1 in six million, the risk in young males with ulcerative colitis taking this combination of drugs increased to 1 in 35,000; a 300-fold increase in risk among this particular group.
Maxx’s parents, Lisa and Stephen Wendell brought an action against the manufacturers of the drugs used to treat his ulcerative colitis and produced two experts who were among the world’s leading experts on T-cell lymphomas. Both of the experts testified that the absolute rarity of the disease generally, combined with the highly specific incidence in young male patients with ulcerative colitis taking a particular combination of drugs, made it more likely than not that Maxx’s HSTCL was caused by the use of these medications; particularly in the absence of any other risk factors. Both experts testified that they relied upon differential diagnosis in reaching this conclusion even in the face of no epidemiologic studies which they explained would be impossible to conduct given the rarity of the disease.
The district court excluded the opinions of these experts under Daubert v. Merrill Dow, finding their opinions unreliable because not based on epidemiologic studies and because their opinions were formed for litigation purposes and not for publication in the medical literature. On appeal, the 9th Circuit reversed holding that the district court “looked too narrowly at each individual consideration, without taking into account the broader picture of the experts’ overall methodology . . . [and] improperly ignored the experts’ experience, reliance on a variety of literature and studies, and review of Maxx’s medical records and history, as well as the fundamental importance of differential diagnosis by experienced doctors treating troubled patients.” The appeals court took particular aim at the over-reliance on the existence or absence of epidemiological studies as a criteria for evaluating the reliability of an expert’s methodology for Daubert purposes noting its fundamental unavailability in the cases of rare dieases:
Perhaps in some cases there will be a plethora of peer reviewed evidence that specifically shows causation. However, such literature is not required in each and every case. “The first several victims of a new toxic tort should not be barred from having their day in court simply because the medical literature, which will eventually show the connection between the victims’ condition and the toxic substance, has not yet been completed.
Thus, court concluded “[i]n the case of a rare disease like HSTCL, the Supreme Court’s mandate that in determining the admissibility of expert testimony, the focus ‘must be solely on principles and methodology, not on the conclusions that they generate’ is especially important.” And, “[w]here, as here, the experts’ opinions are not the ‘junk science’ Rule 702 was meant to exclude, the interests of justice favor leaving difficult issues in the hands of the jury and relying on the safeguards of the adversary system—’vigorous cross-examination, presentation of contrary evidence, and careful instruction on the burden of proof’—to ‘attack shaky but admissible evidence.’”
The case has significant implications for the admission of expert testimony in cases involving rare diseases for which no epidemiologic evidence either doesn’t exist or may never exist because of the disease’s rarity. The broader import of the decision is a rejection of what has become an almost mechanical binary gatekeeping application of Daubert heavily reliant on the presence or absence of epidemiology. The decision recognizes that reliable opinions can be based upon multiple factors and district courts must (at least in the 9th Circuit) be sensitive to the context in which the expert opinions are formulated.
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