There is growing interest in the health correlates of people detained in police custody, and a number of innovations have been introduced to try to meet the complex needs of detainees. The implementation of Criminal Justice Liaison and Diversion (CJL&D) Services commissioned by the Department of Health in England is a substantial part of this investment. In this paper, we describe data from 858 detainees who were referred to the CJL&D service of a busy metropolitan police station in the North East of England. The detainees referred to the service had complex mental health needs, substance misuse and a range of vulnerabilities requiring specific intervention. The effective operation of these teams and how they interface with health and criminal justice systems also depend upon a number of systematic issues that emanate both from within the teams, and from external policy drivers.