The state of Washington follows the Frye test for the admissibility of expert witness testimony. In re Detention of Pettis, 352 P.3d 841 (Wash. Ct. App. 2015). Under this test, expert witness testimony is admissible if “(1) the scientific theory or principles upon which the evidence is based has gained general acceptance in the relevant scientific community of which it is a part; and (2) there are generally accepted methods of applying the theory or principles in a manner capable of producing reliable results.” Id. To be admissible, the court does not have to determine or find that the expert’s theory is correct, it just has to find that the theory is generally accepted by scientists. Id. Further, parties can offer other materials, such as scientific literature, to show the general acceptance of their expert’s theory. Id.
