Washington Revised Code Title 9. Crimes and Punishments § 9.94.040. Weapons--Possession, etc., by prisoner prohibited--Penalty

(1) Every person serving a sentence in any state correctional institution who, without legal authorization, while in the institution or while being conveyed to or from the institution, or while under the custody or supervision of institution officials, officers, or employees, or while on any premises subject to the control of the institution, knowingly possesses or carries upon his or her person or has under his or her control any weapon, firearm, or any instrument which, if used, could produce serious bodily injury to the person of another, is guilty of a class B felony.

(2) Every person confined in a county or local correctional institution who, without legal authorization, while in the institution or while being conveyed to or from the institution, or while under the custody or supervision of institution officials, officers, or employees, or while on any premises subject to the control of the institution, knowingly possesses or has under his or her control any weapon, firearm, or any instrument that, if used, could produce serious bodily injury to the person of another, is guilty of a class C felony.

(3) The sentence imposed under this section shall be in addition to any sentence being served.