In a recent case involving the City of Pomona (“Pomona”) v. SQM North America Corporation (“SQM”), Pomona alleged that SQM’s importation of sodium nitrate for fertilizer caused a perchlorate contamination in the city. Although the district court excluded under Daubert the expert testimony of Pomona’s expert witness on causation, the Ninth Circuit reversed the ruling, stating that “facts casting doubt on the credibility of an expert witness and contested facts regarding the strength of a particular scientific method are questions reserved for the fact finder”. The case was remanded for trial.
Expert testimony admissibility is governed by Federal Rule of Evidence 702, which states:
“If scientific, technical or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training or education, may testify thereto in the form of an opinion or otherwise, if
(1) the testimony is based upon sufficient facts or data,
(2) the testimony is the product of reliable principles and methods, and
(3) the witness has applied the principles and methods reliably to the facts of the case.”
The Supreme Court interpreted this rule in Daubert v. Merrell Dow Pharma., Inc., as providing judges “some gatekeeping responsibility in deciding questions of the admissibility of proffered expert testimony.” The Daubert ruling also emphasized that the trial court must assess the principles and methodology, not on the conclusions generated:
“vigorous cross examination, presentation of contrary evidence, and careful instruction on the burden of proof are the traditional and appropriate means of attacking shaky but admissible evidence”
Additional discussion regarding Daubert criteria applied in this and other cases can be found in this related article.