The First Circuit Court of Appeals has determined that a district court abused its discretion by excluding the general causation testimony of the plaintiffs’ toxicologist in a case involving benzene exposure that allegedly caused a refrigeration technician’s rare leukemia.Milward v. Acuity Specialty Prods. Group, Inc., No. 09-2270 (1st Cir., decided March 22, 2011). The lower court excluded the evidence on the ground that it lacked “sufficient demonstrated scientific reliability to warrant its admission under Rule 702.”

According to the appellate court, the toxicologist based his opinion about a causal link between benzene and the plaintiff’s disease on a “weight of the evidence” methodology. The court described the methodology and noted, “The fact that the role of judgment in the weight of the evidence approach is more readily apparent than it is in other methodologies does not mean that the approach is any less scientific.” The court also described how the toxicologist applied the methodology and concluded that his “opinion rests on a scientifically sound and methodologically reliable foundation.” The court explained that the district court, in ruling the opinion inadmissible, relied on (i) “its evaluation of the mechanistic and epidemiological evidence on which Dr. Smith based his opinion,” and (ii) “its understanding of the scientific concept of ‘biological plausibility’ as used by Dr. Smith when he explained his conclusions.”

The court determined that on both points the district court erred, observing “In the end, the court’s exclusion of the testimony was based on its evaluation of the weight of the evidence, which is an issue that is the province of the jury, and on its misperception of the methodology and analysis that provided the basis for Dr. Smith’s opinion.” Accordingly, the First Circuit reversed the judgment entered for the defendants and the ruling excluding the testimony, and remanded for further proceedings.