The authors use both quantitative and qualitative approaches to evaluate the effectiveness of the co-responder approach in Boston to situations where Boston police are called to address incidents that involve individuals with mental illnesses. To meet the needs of the mentally ill, the Boston Police Department developed a partnership with the Boston Emergency Services Team (BEST) of Boston’s Medical Center in which police officers are paired up with clinicians to respond to incidents. The goal is to provide community based psychiatric crisis services to stabilize and divert nonviolent individuals. The program is a model that has proven to be successful in Boston and it’s been used nationally.