The father killing the mother leaves the children effectively without parents. The extended family from both sides will often intervene to offer a home for the children, or at least to have a say in what arrangements are made for the children and how they are to be brought up. Intensely competitive and hostile feelings between the opposing sets of relatives are commonly aroused, and the children may be caught up in a battle reminiscent of the conflict between their parents, which culminated in the death of their mother. I and my colleagues have, as a team, seen more than 300 children who have lost one parent at the hands of the other, and we have been involved in subsequent custody battles as expert witnesses. Based on this experience and using this context as an example, the issues for the family therapist as expert witness in adversarial Court proceedings are presented. A case is described that illustrates the theoretical exposition--including the effectiveness of family therapy from the witness box.