This chapter explains the motivation for the study. A stark reality is that states often fail to provide justice in many communities enduring criminal group violence. Deaths from criminal group violence roughly equal deaths from war between states, intrastate conflict (namely, civil war and insurgency), and terrorism combined. Moreover, criminal group affiliates who engage in the violence do so with near impunity in many communities. Criminal groups’ ability to escape accountability means that these communities face what I term vacuums of justice. The chapter goes on to argue that justice provision is a core responsibility of the state and, by failing in this regard, states shirk one of their raisons d’être (reasons for existence) under the social contract. The chapter’s final section explains the link between justice provision and cooperation with the police, positing that the police’s reliance on information from witnesses often makes cooperation a necessary albeit insufficient linchpin for justice provision.