Domestic violence is a major social problem worldwide.   In the United States, the failure of communities and police departments to intervene resulted in a push to adopt and implement pro and mandatory arrest policies for domestic violence.  These policies have led to an unexpected increase in the number of arrests of women. Competing explanations have been offered.  This paper describes the development of a system dynamics model of women arrested for domestic violence.  Results suggest that these policies may have created or strengthened a crossover mechanism that shifts the risk of arrests in domestic violence cases from men to women.  Model analysis demonstrates how the changing role of cooperation between advocates and police can help explain the trends in women arrests.  Implications for research and policy are discussed.