Many criminal justice mental health diversion and liaison teams are under threat of extinction. Nacro (2005) notes a steady decline in their number, despite the fact that these schemes in principle provide a valuable service and can fit any social inclusion or crime preventative agenda. In order for such teams and schemes to thrive they need to be strengthened urgently, a point concurred with by Jack Straw when he asked Lord Bradley to undertake a review into mental health diversion as a means of reducing the prison population. But before these schemes can thrive they must survive. We, therefore, argue that research into their sustainability is required and here we introduce a tool we developed (MHEP-AC) that is now in use for that purpose.