Washington Revised Code Title 10. Criminal Procedure § 10.77.030. Establishing insanity as a defense

(1) Evidence of insanity is not admissible unless the defendant, at the time of arraignment or within ten days thereafter or at such later time as the court may for good cause permit, files a written notice of his or her intent to rely on such a defense.

(2) Insanity is a defense which the defendant must establish by a preponderance of the evidence.

(3) No condition of mind proximately induced by the voluntary act of a person charged with a crime shall constitute insanity.