(1) A power of attorney must be signed and dated by the principal, and the signature must be either acknowledged before a notary public or other individual authorized by law to take acknowledgments, or attested by two or more competent witnesses who are neither home care providers for the principal nor care providers at an adult family home or long-term care facility in which the principal resides, and who are unrelated to the principal or agent by blood, marriage, or state registered domestic partnership, by subscribing their names to the power of attorney, while in the presence of the principal and at the principal's direction or request.

(2) A power of attorney shall be considered signed in accordance with this section if, in the case of a principal who is physically unable to sign his or her name, the principal makes a mark in accordance with RCW 11.12.030, or in the case of a principal who is physically unable to make a mark, the power of attorney is executed in accordance with RCW 64.08.100.

(3) A signature on a power of attorney is presumed to be genuine if the principal acknowledges the signature before a notary public or other individual authorized by law to take acknowledgments.