Diversion programs aim to reduce time in jail for individuals with mental illness, particularly those arrested for minor offenses, and work to connect individuals with resources to reduce recidivism risk. Pretrial diversion for individuals with mental illness takes a variety of forms across the criminal justice and legal sectors, and generally involves the healthcare sector (i.e. behavioral and physical health). Diversion efforts often transfer individuals with serious mental illness (SMI) and substance use disorder (SUD) to the healthcare sector and often fail to account for all the community costs involved in connecting individuals to services. Although diversion programs differ in nature, we argue that the common link is diversion reduces organizational burden on both the correctional and legal sectors, rather than restoring individuals to functionality in the community. SMI/SUD requires long-term disease management, thus, measuring diversion, reintegration, or restoration over a 12-month period does not capture the chronic nature of the illness. Diversion success does not equate to a risk level of recidivism resembling non-justice-involved individuals. Rather reincarceration risk reduction for the long term may require lifetime management. We propose a model that challenges evaluators to present more standardized and comprehensive assessment of outcomes and costs in pretrial diversion spanning criminal justice, legal, and healthcare sectors. Public health can provide clarity to the field by providing a population viewpoint of diversion within and between the criminal justice, legal, and healthcare systems to unify understanding of diversion. Using a public health lens, the chapter will describe: 1) Deinstitutionalization of persons with mental illness (policy, healthcare, criminal justice, legal), 2) Criminological Risks for an individual versus a population with mental illness, 3) Metrics to compare diversion programs, 4) Unifying diversion research agendas across criminal justice, legal, and healthcare systems.