Crime can be costly to society, and incarceration can also be costly: to the government that funds prisons, and to the individuals whose freedoms are curtailed. Criminal justice reform focuses on improving the criminal justice and prison systems to reduce these imprisonment costs.
Criminal justice reform is particularly promising in the United States. It is also unusually tractable, due to the adverse US fiscal situation and the confluence of liberal and conservative interest in this area. For these reasons, the Open Philanthropy Project considers criminal justice reform a promising intervention, and has funded several charities working in this space (Open Philanthropy Project 2016).
Open Philanthropy Project. 2016. Criminal justice reform.