Evidence Rules for Admission of Expert Testimony in Washington State
Cathy Johnston-Forbes v Dawn Matsunaga (August 28, 2014 WSC)
In the context of a dispute over the admissibility of a biomechanical expert’s testimony, the Washington Supreme Court provided the most current summary of expert testimony law in Washington State:
Generally, expert testimony is admissible if (1) the expert is qualified, (2) the expert relies on. generally accepted theories in the scientific community, and (3) the testimony would be helpful to the trier of fact. In applying this test, trial courts are afforded wide discretion and trial court expert opinion decisions will not be disturbed on appeal absent an abuse of such discretion. In re Marriage of Katare, 175 \Vn.2d 23, 38, 283 P.3d 546 (2012), cert. denied, _ U.S. __, 133 S. Ct. 889, 184 L. Ed. 2d 661 (2013). If the basis for admission of the evidence is ‘”fairly debatable,”‘ we will not disturb the trial court’s ruling. Grp. Health Coop. of Puget Sound, Inc. v. Dep’t of Revenue, 106 Wn.2d 391, 398, 722 P.2d 787 (1986) (internal quotation marks omitted) (quoting Walker v. Bangs, 92 Wn.2d 854, 858, 601 P.2d 1279 (1979)).
In Washington, there are four main Evidence Rules regarding the use of expert witnesses. ER 702 generally establishes when expert testimony may be utilized at trial: “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.”
ER 703 allows an expert to base his or her opinion on evidence not admissible in evidence and to base his or her opinion on facts or data perceived by or made known to the expert at or before the hearing.2 ER 704 allows an expert to testify on an ultimate issue the trier of fact must resolve.3 Finally, ER 705 indicates that an expert need not disclose the facts on which his or her opinion is based, although the court may require their disclosure and the expert may be subject to cross-examination on them.