Source: (2007) In John Hamel and Tonia L. Nicholls, Ed., Family Interventions in Domestic Violence. New York, USA: Springer Publishing Company. Pp. 457-475.

"...These court battles are often referred to qualified custody evaluators who employ a complex system of clinical interview, psychological evaluations, and collateral interviews (Austin, 2001; Gould, 1998). In the initial interviews, parties are often asked about their perceptions of the other parent and their parenting skills, time spent with the children, and other factors that could affect percentage of custody granted. Three major conditions that can affect a parent's custody share in these cases are mental instability, substance, abuse, and family abuse (intimate partner as well as child abuse or neglect). There are many methods available to assess for mental instability and drug use; however, family abuse accusations are much harder to assess for and often get caught up in "he said/she said" allegations." (excerpt)