RAP 12.1: BASIS FOR DECISION
(a) Generally. Except as provided in section (b), the appellate court will decide a case only on the basis of issues set forth by the parties in their briefs.
(b) Issues Raised by the Court. If the appellate court concludes that an issue which is not set forth in the briefs should be considered to properly decide a case, the court may notify the parties and give them an opportunity to present written argument on the issue raised by the court.