In short - in Missouri, a Guardian ad Litem is an attorney who represents the best interests of a child or children in, for example, a custody matter. Missouri’s Revised Statutes Section 452.423 states that a Guardian ad litem [is to be] appointed...1. In all proceedings for child custody or for dissolution of marriage or legal separation where custody, visitation, or support of a child is a contested issue, the court may appoint a guardian ad litem. 2. The court shall appoint a guardian ad litem in any proceeding in which child abuse or neglect is alleged.