Wash. Rev. Code § 26.44.190
A law enforcement agency shall not allow a law enforcement officer to participate as an investigator in the investigation of alleged abuse or neglect concerning a child for whom the law enforcement officer is, or has been, a parent, guardian, or foster parent. This section is not intended to limit the authority or duty of a law enforcement officer to report, testify, or be examined as authorized or required by this chapter, or to perform other official duties as a law enforcement officer.
RCW 26.44.190
Findings-Intent-1999 c 389 s 9: "The legislature finds that the parent, guardian, or foster parent of a child who may be the victim of abuse or neglect may become involved in the investigation of the abuse or neglect. The parent, guardian, or foster parent may also be made a party to later court proceedings and be subject to a court-ordered examination by a physician, psychologist, or psychiatrist. It is the intent of the legislature by enacting section 9 of this act to avoid actual or perceived conflicts of interest that may occur when the parent, guardian, or foster parent is also a law enforcement officer and is assigned to conduct the investigation of alleged abuse or neglect concerning the child." [ 1999 c 389 s 8.]