The New Mexico Court of Appeals affirmed the exclusion of an expert opinion seeking to establish general causation between exposure to petrochemicals and autoimmune conditions, including lupus, and affirmed a trial judgment in favor of the defendants, Shell Western Exploration and Production, Inc. and Shell Oil Company, on all remaining claims. Acosta v. Shell Western Exploration and Production, Inc., Case No. 29,502 (N.M. Ct. App., Oct. 2, 2012).

The plaintiffs were eight out of more than 200 residents of a neighborhood in Hobbs, N.M., who alleged toxic exposure to petrochemicals that were detected in soil and groundwater in an area where crude oil had been extracted from an active oilfield. New Mexico law requires expert testimony to establish both general and specific causation in a toxic tort case. The plaintiffs’ expert, Dr. James Dahlgren, intended to testify to a reasonable degree of medical certainty that exposure to a mixture of three chemicals found in crude oil -- pristane, benzene and mercury -- caused various autoimmune conditions suffered by the plaintiffs.

Dr. Dahlgren primarily based his general causation opinion on his own epidemiologic study. Dr. Dahlgren compared data based on blood samples and questionnaires from the plaintiff group with similar data from an unexposed group of California residents. He concluded that there was a higher prevalence of various medical conditions, ranging from respiratory complaints to lupus, in the exposed group, and opined that exposure to pristane and mercury may induce lupus. The study was not designed to determine whether or at what levels the petrochemicals would cause autoimmune disorders. The plaintiffs attempted to explain how Dr. Dahlgren’s methodology and principles could overcome the usual limitations of a cross-sectional analysis in determining a causal link. The Court of Appeals, however, did not need to address the reliability of the underlying methodology because the study itself did not purport to establish the necessary nexus between the underlying data and the expert’s opinions regarding causation, observing that “[w]hile it is true that epidemiologic studies are generally used as proof of causation, not all epidemiologic studies can establish causation.” Id. at p.16. The District Court of Lea County, New Mexico, granted partial summary judgment based on the alleged autoimmune injuries after excluding Dr. Dahlgren’s opinion, but tried the case on the plaintiffs’ remaining personal injury and property damage claims associated with negligence, strict liability, nuisance and trespass counts.

The trial resulted in a defense jury verdict on all claims. The Court of Appeals affirmed the court’s final judgment as well as its denial of the plaintiffs’ motion for a new trial based on purported juror misconduct. New Mexico juries are permitted to discuss evidence throughout the course of a trial, UJI 13-110 NMRA, and the Court of Appeals determined that the District Court did not abuse its discretion in finding that isolated comments attributed to certain jurors during the trial fell short of demonstrating a fixed predetermination of the final outcome of the case.