Wash. Rev. Code § 12.16.030
Whenever it shall appear to the satisfaction of the justice, by proof made before him or her, that any person, duly subpoenaed to appear before him or her in an action, shall have failed, without a just cause, to attend as a witness, in conformity to such subpoena, and the party in whose behalf such subpoena was issued, or his or her agent, shall make oath that the testimony of such witness is material, the justice shall have the power to issue an attachment to compel the attendance of such witness: PROVIDED, That no attachment shall issue against a witness in any civil action, unless his or her fees for mileage and one day's attendance have been tendered or paid in advance, if previously demanded by such witness from the person serving the subpoena.
RCW 12.16.030
Attachment of a witness: RCW 5.56.070.
When witness must attend: RCW 5.56.010.