Washington Revised Code Title 11. Probate and Trust Law § 11.130.710. Presumption of capacity

(1) All adults are presumed to be capable of managing their affairs.

(2) The manner in which an adult communicates with others is not grounds for deciding that the adult is incapable of managing the adult's affairs.

(3) Execution of a supported decision-making agreement may not be used as evidence for the petition or appointment of a guardianship or conservatorship under this chapter, and does not preclude the ability of the adult who has entered into such an agreement to act independently of the agreement.