(1)(a) The court may order an investigation and report concerning parenting arrangements for the child, or may appoint a guardian ad litem pursuant to RCW 26.12.175, or both. The investigation and report may be made by the guardian ad litem, court-appointed special advocate, the staff of the juvenile court, or other professional social service organization experienced in counseling children and families.

(b) An investigator is a person appointed as an investigator under RCW 26.12.050(1)(b) or any other third-party professional ordered or appointed by the court to provide an opinion, assessment, or evaluation regarding the creation or modification of a parenting plan.

(2) In preparing the report concerning a child, the investigator or person appointed under subsection (1) of this section may consult any person who may have information about the child and the potential parenting or custodian arrangements. Upon order of the court, the investigator or person appointed under subsection (1) of this section may refer the child to professional personnel for diagnosis. The investigator or person appointed under subsection (1) of this section may consult with and obtain information from medical, psychiatric, or other expert persons who have served the child in the past without obtaining the consent of the parent or the child's custodian; but the child's consent must be obtained if the child has reached the age of twelve, unless the court finds that the child lacks mental capacity to consent. If the requirements of subsection (3) of this section are fulfilled, the report by the investigator or person appointed under subsection (1) of this section may be received in evidence at the hearing.

(3) The investigator or person appointed under subsection (1) of this section shall provide his or her report to counsel and to any party not represented by counsel at least ten days prior to the hearing unless a shorter time is ordered by the court for good cause shown. The investigator or person appointed under subsection (1) of this section shall make available to counsel and to any party not represented by counsel his or her file of underlying data and reports, complete texts of diagnostic reports made to the investigator or appointed person pursuant to the provisions of subsection (2) of this section, and the names and addresses of all persons whom he or she has consulted. Any party to the proceeding may call the investigator or person appointed under subsection (1) of this section and any person whom the investigator or appointed person has consulted for cross-examination. A party may not waive the right of cross-examination prior to the hearing.