Evidence – Expert Witness Testimony – Grounds for Exclusion


City of Pomona v. SQM North America Corporation
Court Of Appeals, Ninth Circuit Nos. 12-55147, 12-55193 (May 2, 2014)

Under Federal Rule of Evidence (“FRE”) 702, expert witness testimony must meet certain criteria to be admissible.  In Daubert v. Merrill Dow Pharmaceuticals (1993) 509 U.S. 579,  the United States Supreme Court held that section 702 incorporated a “flexible reliability standard,” rather than limiting testimony to that which was “generally accepted” in the field.  This case considered opinion testimony of an environmental expert to compare/identify perchlorates in a water aquifer.
The City of Pomona, California (“Pomona”) administers a public water system sourced from the Chino Basin aquifer, which feeds into Pomona’s groundwater treatment facility.  In 2007, Pomona discovered that the aquifer had levels of the chemical perchlorate in excess of the Maximum Contaminant Level permitted by the California Department of Public Health (“CDPH”).  The CDPH regulates contaminants in drinking water by implementing certain standards requiring notification and remediation if levels approach and/or exceed the maximum contaminant levels.  In October, 2010 Pomona filed suit against SQM North America Corporation (“SQMNA”) to recover the cost of investigating and remediating perchlorate contamination in the groundwater.  Pomona alleged that SQMNA’s importation of natural sodium nitrate from the Atcama Desert in Chile for fertilizer use was the primary source of Pomona’s perchlorate contamination. 
At trial the district court held a Daubert evidentiary hearing to consider SQMNA’s pretrial motion in limine to exclude the testimony of Dr. Neil Sturchio, Pomona’s expert witness regarding causation.  Dr. Sturchio is the Director of the Environmental Isotope Geochemistry Laboratory at the University of Illinois at Chicago.  He was charged with determining the origin of Pomona’s perchlorate contamination using a scientific methodology known as “stable isotope analysis.”  Under his direction, Wildermuth Environmental, Inc. collected samples from the Pomona groundwater using methods based on the Guidance Manual for Forensic Analysis of Perchlorate in Groundwater using Chlorine and Oxygen Isotopic Analysis (“Guidance Manual”).  Dr. Sturchio compared the composition of the perchlorate in Pomona’s groundwater with a reference database of known perchlorate sources to determine its origin.  Dr. Sturchio used a four-step methodology to conduct his testing and disclosed it in his expert report.  The methodology was also published in 2011 in the Guidance Manual, which was commissioned by the Environmental Security Technology Certification Program of the United States Department of Defense.  Prior to publication in the Guidance Manual, peer review articles included descriptions of the stable isotope analysis used by Dr. Sturchio and his colleagues. 
Dr. Sturchio opined that the dominant source of perchlorate in the Pomona groundwater was from the Atacama Desert in Chile.  Based on Dr. Sturchio’s findings, Pomona sought to introduce expert testimony at trial that the perchlorate found in its groundwater had the same properties as the perchlorate SQMNA imported into southern California from Chile between 1927 and the 1950s.  SQMNA moved to exclude Sturchio’s opinions, arguing that the “stable isotope analysis” failed to satisfy Daubert and was insufficiently reliable to be received into evidence under FRE 702. The district court held an evidentiary hearing and granted SQMNA’s motion in limine to exclude Dr. Sturchio’s testimony.  The district court reasoned that Dr. Sturchio’s opinions were unreliable because:  (1) his opinions were subject to future methodological revisions that were not yet certified; and (2) the procedures he used had not yet been tested and were not subject to retesting; and (3) the reference database used by Dr. Sturchio was too small. 
The Ninth Circuit reversed the ruling of the district court excluding Dr. Sturchio’s testimony.  Under FRE 702, expert opinion is admissible if:  (1) the witness is sufficiently qualified as an expert by knowledge, skill, experience, training, or education; (2) the scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to make a fact determination; (3) the testimony is based on sufficient facts or data; (4) the testimony is the product of reliable principles and methods; and (5) the expert has reliably applied the relevant principles and methods to the facts of the case.  The Ninth Circuit also reviewed Daubert andDaubert II, which held that a district court’s determination of the admissibility of expert testimony is flexible.  In evaluating admissibility, the trial court is “a gatekeeper, not a fact finder.”  The trial court’s responsibility is to insure that expert opinion is relevant and is based on knowledge and experience in the relevant discipline.  The soundness of the scientific methodology is most important to the analysis.  In evaluating methodology, the court should use criteria such as testability, publication in peer-reviewed literature, known or potential error rate and general acceptance in the scientific community.  Nonsensical opinions are subject to exclusion.  However, disputable but admissible expert testimony is to be attacked by cross-examination and contrary evidence.  Credibility of the expert’s opinion is for a jury to decide.
The Ninth Circuit rejected the district court’s determination that Dr. Sturchio’s procedures were not reliable as an abuse of discretion.  The fact that the method was not yet EPA certified did not render it inadmissible and/or unreliable under FRE 702.  Ongoing research regarding Guidance Manual Standards did not invalidate the reliability of expert testimony.  The methods used by Dr. Sturchio were subject to inter-laboratory calibration and collaboration among the world’s leading experts.  The method was practiced by a minority of scientists in the field and was subject to peer review for ten years.  Because Dr. Sturchio did not take dual samples or have a separate laboratory independently verify his results did not render his method defective.  Proper adherence to Guidance Manual protocols was an issue for the jury to determine.  The Ninth Circuit reiterated the rule of law that “only faulty methodology or theory, as opposed to imperfect execution of laboratory techniques, is a valid basis to exclude expert testimony.”  The district court’s ruling that Dr. Sturchio’s reference database was too small to opine regarding the origin of the perchlorate was incorrect.  Any controversy regarding extrapolated findings should be resolved by the fact finder after a “battle of the experts” – not judicial exclusion.
Under Daubert and FRE 702, a district court should be flexible in admitting expert opinion.  As long as an expert’s opinion is supported by adequate foundation and is reliable, it should be allowed to be presented to the fact finder to make the ultimate ruling on credibility.  The most important factor in admissibility is whether the methodology employed is generally accepted by the scientific community.
For a copy of the complete decision, see:


DISCLAIMER: Because of the generality of this update, the information provided herein may not be applicable in all situations and should not be acted upon without specific legal advice based on particular situations.

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