Toxic Tort Expert WitnessFrom the 1920s through 1993, a Defendant Oil Company engaged in oil and gas operations in New Mexico. Environmental contamination from these operations was discovered much later, and 200+ residents of the contaminated area brought a toxic tort action for personal injury damages that included systemic lupus erythematosus and other autoimmune disorders. The Plaintiffs alleged that toxic chemicals from crude oil caused their illnesses. They challenged the district court’s exclusion of the scientific evidence and expert testimony offered in support of this theory and the resulting partial summary judgment in favor of the Defendant.

The Plaintiffs sought to offer the expert testimony that their lupus and other autoimmune disorders were caused or aggravated by long-term exposure to a mixture of benzene and other toxic chemicals found in crude oil. As support for this causation opinion, the expert provided numerous animal and human studies that linked the agents to immune system disruption, autoimmune diseases, and lupus. His study of Plaintiffs identified 13 diagnosed cases of lupus in two blocks of the neighborhood on or near the exploration location. To explain the prevalence of these diseases in the area compared to the unexposed control community, the expert concluded that the agents caused the statistically significant elevation in occurrences of autoimmune disorders. He presented evidence that the results of the animal observations referenced in his study provided the scientifically valid basis for his causation opinion in this case: he determined that the dose of pristane the Plaintiffs received from prolonged household exposure, adjusted for the weight of a human, was within the range of the potentially “harmful dose” determined in the animal observations. He also discussed several other studies of oilfield outbreaks of autoimmune disease, one of which cited a rate of lupus that was well above the national rate but only one-eighth the rate of lupus found in the Plaintiffs’ neighborhood.

The expert also ruled out several possible alternative explanations for the elevated occurrence of autoimmune disorders and considered all of this evidence before concluding that the Plaintiffs’ inhalation, ingestion, and absorption of the toxins from the Defendant’s oil and gas operations caused or aggravated their lupus and other autoimmune disorders.

The district court excluded the animal studies and the expert’s study itself as not relevant, reasoning they failed to show general causation between the mixture of identified chemicals and lupus. It concluded that the expert’s study had “limited value as a basis for a causal connection opinion” because it was a “hypothetical” study “admittedly done only for comparison purposes.” Therefore, it failed to “bridge the gap from association to causation” and could not stand alone to support the Plaintiffs’ claims of a causal relationship between the alleged mixture and lupus. As a result, the district court excluded the expert’s causation opinion due to “insufficient” evidentiary support and based on the consequential lack of causation evidence. The court granted the Defendant’s motion for summary judgment.

On appeal, the Court of Appeals affirmed the district court’s grant of summary judgment, holding that the district court did not abuse its discretion when it concluded that the expert’s study and the animal studies were “not sufficient” in either bridging the analytical gap from association to causation or in establishing causation between the agents and the Plaintiffs’ lupus and autoimmune disorders. The Court of Appeals interpreted the district court’s evidentiary ruling that the expert’s study didn’t “fit” the case as an issue of relevance, and agreed with the district court.

Justice Charles W. Daniels wrote in his opinion that the admissibility of expert testimony in New Mexico is guided by Rule 11–702 NMRA, which sets out three requirements: (1) that the expert be qualified; (2) that the testimony be of assistance to the trier of fact; and (3) that the expert’s testimony be about scientific, technical, or other specialized knowledge with a reliable basis. Shortly after Daubert, Judge Daniels noted that the New Mexico Supreme Court stated that the “pertinent inquiry” for determining whether expert testimony will assist the trier of fact under the second requirement of Rule 11–702 “must focus on the proof of reliability of the scientific technique or method upon which the expert testimony is premised.”

Since Daubert, the federal courts have continued to refine the standards for admissibility of expert testimony, but New Mexico has not followed these changes in lockstep with the federal courts. Committee commentary on Rule 11–702 warns of the differences between federal and New Mexico law in applying the Daubert requirements.

Justice Daniels of the New Mexico Supreme Court explained that in General Electric Co. v. Joiner, the U.S. Supreme Court affirmed a district court’s determination to exclude an expert’s causation testimony on grounds of relevance, noting that “[a] court may conclude that there is simply too great an analytical gap between the data and the opinion proffered.” Here, both the district court and the Court of Appeals cited this Joiner proposition as a key reason for excluding the expert’s general causation testimony pertaining to the Plaintiffs’ development of lupus and other autoimmune conditions and determined that the analytical gap between the evidence presented and the inference drawn on the ultimate issue of causation was too wide. However, New Mexico has never adopted the Joiner rule that a judge may reject expert testimony where the “analytical gap” between the underlying evidence and the expert’s conclusions is “too great,” and the Court would not do so in this case. Joiner, the Court said, was inconsistent with longstanding state law that leaves credibility determinations and weighing of the evidence to the trier of fact. Citing a 2004 New Mexico Supreme Court decision, Justice Daniels wrote, “Given the capabilities of jurors and the liberal thrust of the rules of evidence, we believe any doubt regarding the admissibility of scientific evidence should be resolved in favor of admission, rather than exclusion.” The Court believed that the expert’s causation opinion, his study, and the animal studies it relied on were relevant and admissible if they demonstrated a valid scientific relationship that is supportive of causation—regardless of whether they totally sustain the Plaintiffs’ entire burden of proof.

Relying on Joiner, when the district court found that the expert’s study “fail[ed] to bridge the gap from association to causation,” it improperly blurred the line between the evidence and in making a judgment about causation. The Supreme Court concluded that the methodology of the expert’s study reinforced a valid scientific inference that was supportive of causation, even if it didn’t conclusively establish that the specific chemicals at issue can cause lupus or other autoimmune disorders. Accordingly, the expert’s study and his causation testimony should have been admitted.


Conception and Rosario Acosta v. Shell Western Exploration, — P.3d —-, 2016 WL 852511 (N.M. March 3, 2016).