Heidi Niemann (plaintiff) and Lyle Niemann (defendant) were divorced, and Heidi received custody of the Niemanns’ son and daughter. Heidi and Lyle subsequently married other people. Six years later, the Niemanns agreed that their daughter would move in with Lyle. Upon learning of two incidents of possible domestic violence in Heidi’s home, Lyle moved for a change of custody of their son. Prior to a hearing, the Niemanns reaffirmed their agreement to the physical change of custody of their daughter from Heidi to Lyle. Additionally, a custody investigator was appointed by the trial court to recommend which party should receive custody of their son. The investigator interviewed Heidi, Lyle, the children, several friends, and family members, and the investigator concluded that custody of the son should be awarded to Lyle. Of particular importance was an instance in which the daughter spoke with a school social worker about a fight involving yelling and swearing between her mother and stepfather that resulted in the destruction of several household items. A second instance involved the stepfather arriving home drunk and yelling and pushing Heidi. A report was consequently filed with social services. The daughter stated that she was scared of her stepfather. The trial judge denied Lyle’s motion and held that no material change in circumstances existed warranting the change of custody of the son from Heidi to Lyle. Lyle appealed.