Across the western world, since the latter part of the twentieth century, people with mental and cognitive disabilities have been funneled into criminal justice systems, remanded, sentenced and imprisoned in larger numbers than previously and in far higher proportions than their presence in the general population. Australian criminal justice systems are no exception. The use of societal punishment and control systems in this manner is a deeply disturbing turn. People with these disabilities who become enmeshed with the police, courts and prisons are largely from the most disadvantaged backgrounds and communities, with Indigenous Australians significantly over-represented amongst them. As criminal justice processes are primarily to assess guilt and administer punishment, they tend to intensify experiences of disability; prison is not a therapeutic place. So why are there so many people with mental and cognitive disability incarcerated? Evidence from recent studies and cases suggest that at heart, this is a matter of how Australian society supports, enacts social justice for and affords human rights to the most vulnerable people.