Wash. Rev. Code § 30A.22.220
Notwithstanding RCW 30A.22.210, a financial institution may, without liability, pay or permit withdrawal of any funds on deposit in an account to a depositor and/or agent of a depositor and/or trust or P.O.D. account beneficiary, and/or other person claiming an interest therein, even when the financial institution has actual knowledge of the existence of the dispute, if the adverse claimant shall execute to the financial institution, in form and with security acceptable to it, a bond in an amount which is double either the amount of the deposit or the adverse claim, whichever is the lesser, indemnifying the financial institution from any and all liability, loss, damage, costs, and expenses, for and on account of the payment of the adverse claim or the dishonor of the check or other order of the person in whose name the deposit stands on the books of the financial institution: PROVIDED, That where the person in whose name the deposit stands is a fiduciary for the adverse claimant, and the facts constituting such relationship, and also the facts showing reasonable cause of belief on the part of the claimant that the fiduciary is about to misappropriate the deposit, are made to appear by the affidavit of the claimant, the financial institution shall, without liability, refuse to deliver the property for a period of not more than five business days from the date that the financial institution receives the adverse claimant's affidavit, without liability for the sufficiency or truth of the facts alleged in the affidavit, after which time the claim shall be treated as any other claim under this section.
RCW 30A.22.220