The primary issue in City of Pomona v. SQM North America Corporation (2014) __F.3d__, involves a dispute over the reliability of expert evidence presented to a trial court and that trial court’s decision to exclude the expert’s opinion as unreliable. The litigation began with petitioner City of Pomona’s efforts to remediate its water supply of perchlorate contamination in order to comply with California drinking water standards.

The City hired the environmental consulting firm Wildermuth Environmental, Inc. to investigate perchlorate contamination. The firm’s expert, Dr. Sturchio, used a testing methodology known as “stable isotope analysis” to identify the potential sources of perchlorate contamination. Based on this testing, Dr. Sturchio concluded that the majority of perchlorate contamination in Pomona’s groundwater could be traced to the Atacama Desert in Chile.

Using Dr. Sturchio’s findings, the City of Pomona argued that the perchlorate contamination in its groundwater had the same distinctive isotopic properties as perchlorate imported from Chile by SQM North America Corporation (“SQMNA”) between 1927 and the 1950’s. The city initiated litigation against SQMNA to recover costs of investigating and remediating perchlorate contamination in the city’s groundwater supply.

During pre-trial proceedings, SQMNA filed a motion to exclude Dr. Sturchio’s report, arguing the expert testimony was unreliable and therefore inadmissible under the Federal Rules of Evidence, rule 702. Rule 702 admits expert opinion into evidence where: 1) the witness is sufficiently qualified as an expert; 2) the expert’s knowledge will help the trier of fact to understand evidence or a fact in issue; 3) the expert’s testimony is based upon sufficient facts or data; 4) the expert’s testimony is based on reliable principles and methods; and 5) the principles or methods have been reliably applied by the expert to the facts of the case.  Under the long established “Daubert rule,” a court’s inquiry into the admissibility of expert opinion under rule 702 is flexible. In evaluating the admissibility of expert testimony, the court is “a gatekeeper, not a fact finder.” In other words, the role of the court is not to decide whether the expert is right or wrong as a matter of law, but whether the testimony is reliable and will be helpful to the finder of fact.

In this case, the district court concluded that Dr. Sturchio’s procedures were not sufficiently reliable because they are not generally accepted in the scientific community. The court pointed to three factors in support of this conclusion. First, the quality assurance/quality control (“QA/QC”) parameters for stable isotope analysis were still being refined. Second, the EPA had not yet certified stable isotope analysis for organic or inorganic compounds. And third, the methodology employed by the expert was not subject to retesting. But the Ninth Circuit disagreed, finding the district court’s reasoning insufficient to justify exclusion of Dr. Sturchio’s testimony.

The appellate court explained that scientific methods are not necessarily unreliable simply where they are subject to “further testing and refinement.” In reaching this conclusion, the appellate court displayed a sophisticated understanding of the scientific method. The scientific method relies on observation and the collection of data. Theories are developed based on these observations and data sets. But new observations and data are continually gathered and may point to a need for refinement of previously accepted theories. In this fashion, scientific theories are credible not because they have been proven “correct,” but because they have not yet been proven false. And while this may seem like an unnecessary exercise in semantics, the distinction is important to a fundamental understanding of the scientific method. As the appellate court succinctly stated: “There are no certainties in science.” That an expert’s method is subject to further testing and refinement is insufficient to render that expert’s opinion unreliable and inadmissible.

The appellate court also rejected the notion that Dr. Sturchio’s methods were not reliable simply because they were not certified by the EPA. The standard for testing the reliability of an expert’s methods is whether some objective source shows the expert’s conclusions are based on a scientific method practiced by at least a minority of recognized experts in the field, not whether the methods have been certified by the EPA or another government agency. Dr. Sturchio employed a method for the stable isotope study of chlorine and oxygen in perchlorate present in groundwater. And this testing method was based on the 2011 publication Guidance Manual for Forensic Analysis of Perchlorate in Groundwater Using Chlorine and Oxygen Isotopic Analyses, which was reviewed by other laboratories and subject to inter-laboratory calibration.  Furthermore, other leading experts in the field have employed the same methodology. These factors indicate that the stable isotope analysis was reliable, despite a lack of EPA certification.

Next, the appellate court addressed whether the expert opinion met the requirement of rule 702 that the methodology be subject to retesting. The district court criticized Dr. Sturchio for not taking dual samples, thereby making it impossible for other laboratories to verify the conclusions using the same exact data-set. But the appellate court determined the trial court applied the standard admissibility incorrectly. Under Daubert, testability of expert opinion is described in the context of a hypothesis that is falsifiable. In this case, other laboratories have employed the same methods used to analyze Pomona’s groundwater. Moreover, there is a distinction between whether the methodology used by an expert is subject to retesting and whether that expert took field samples properly. SQMNA’s criticisms focused on Dr. Sturchio’s sampling procedures and his failure to take dual samples. While this criticism may go to the weight afforded to the expert opinion, criticizing the expert’s samples is insufficient to show the methodology employed to reach the ultimate scientific conclusion is unreliable and should be excluded from evidence.

Finally, the appellate court addressed an issue familiar to CEQA practitioners: the battle of the experts. At trial, an expert for SQMNA argued Dr. Sturchio’s reference database was too limited for him to reliably identify and comment on the potential sources of perchlorate contamination in the city’s water. Dr. Sturchio naturally disagreed and defended his methodology in reply. The trial court found the uncertainty raised by SQMNA’s expert a compelling reason to exclude Dr. Sturchio’s opinion, but the Ninth Circuit noted that Daubert does not require such certainty for admitting expert testimony. Experts often disagree, and it was an abuse of discretion for the trial court to side with SQMNA’s expert over the city’s expert.  Instead, it was the role of the trier of fact—here, the jury—to resolve the conflicting expert testimony. Dr. Sturchio’s expert opinion should have been admitted.

This case, while not a CEQA case, provides useful guidance for CEQA and NEPA practitioners, as the reliability of expert opinion can often be an issue in litigation challenging environmental review. It also serves as an important reminder that a battle between experts is insufficient to establish unreliability. The fact finder in CEQA cases is the lead agency approving the project. When approving a project, the lead agency ultimately exercises its judgment in deciding how much weight to assign expert opinion. So when reviewing work produced by experts, like environmental consultants, CEQA practitioners should note to what extent the record supports that expert’s credibility. A robust record can assist practitioners in defending their expert’s credibility from attacks by experts hired by opponents.