Expert Witness In Federal Court Improperly Excluded.

In a case involving excessive chemical levels in a city’s water system, the city’s expert witness used a four-step methodology, which methodology was published in a manual commissioned by the Environmental Security Technology Certification Program of the U.S. Department of Defense. Based on his methodology, the expert gave his opinion of the dominant source of the chemical found in the water. The trial court granted defendant’s motion to exclude the expert’s testimony on the grounds that: (1) the opinions were subject to future methodological revisions and not yet certified; (2) the procedures he used had not yet been tested and were not subject to retesting; and (3) the reference database used by the expert was too small. The Ninth Circuit found the district court erred, stating: “Expert testimony may be excluded by a trial court under Rule 702 of the Federal Rules of Evidence only when it is either irrelevant or unreliable. Facts casting doubt on the credibility of an expert witness and contested facts regarding the strength of a particular witness are questions reserved for the fact finder.” (City of Pomona v. SQM North America Corp. (Ninth Cir.; May 2, 2014) 750 F.3d 1036.)