Most jurisdictions now have legislation requiring courts to consider domestic violence in making custody and visitation determinations (Family Violence Project of the National Council of Juvenile and Family Court Judges, Family Violence in Child Custody Statutes, 1995).
The Model Code drafted by the National Council of Juvenile and Family Court Judges Advisory Committee on Family Violence provides that a finding of domestic violence creates a presumption that it is not in the child's best interest to be placed in the sole or joint custody of the perpetrator (Family Violence: A Model State Code (PDF 1.07MB), § 403, 1994).
Joint custody is not appropriate when there is a history of domestic violence in the family. Joint custody presupposes the parents' ability to engage in constructive conversation and decision-making concerning their child. Domestic violence renders that type of collaboration nearly impossible.
Most jurisdictions now have legislation requiring courts to consider domestic violence in making custody and visitation determinations. A state-by-state chart presenting statutes and their various provisions (PDF 194KB) is available from the American Bar Association Commission on Domestic Violence.