Wash. Rev. Code § 68.64.050
(1) Subject to RCW 68.64.070, a donor or other person authorized to make an anatomical gift under RCW 68.64.030 may amend or revoke an anatomical gift by:
(a) A record signed by:
(2) A record signed pursuant to subsection (1)(a)(iii) of this section must:
[ 2008 c 139 s 6.]