RCW 11.20.030

If any witness be prevented by sickness from attending at the time any will is produced for probate, or reside out of the state or more than thirty miles from the place where the will is to be proven, such court may issue a commission annexed to such will, and directed to any judge, notary public, or other person authorized to administer an oath, empowering him or her to take and certify the attestation of such witness.