The Conclusion first summarizes the study’s findings. It then presents the study’s policy implications that might help inform local actors’ decisions on interventions related to police–citizen cooperation in communities with criminal groups. Additional research questions are also proposed. In particular, how the study’s findings might relate to contexts experiencing political violence such as civil war or insurgency remains an avenue for future research. The final section highlights that populations are projected to grow fastest in countries with strong criminal groups and weak state institutions for fighting those groups. This trend increases the urgency to understand vacuums of justice and how they might be filled.

This chapter presents the results of a survey experiment testing cooperation interventions in Lagos. It provides background information on the relatively limited efforts to date to promote police–citizen cooperation in the megacity. The chapter describes the virtual reality–based survey experiment used to test the interventions in which respondents are shown a hypothetical area boy fight from a shopkeeper’s point of view. The results indicate that respondents who viewed the vignettes with an anonymous tip line and the intervention to raise awareness of cooperation support among shopkeepers boosts information sharing. Exposure to co-ethnic police officers in the vignette, however, shows little effect on information sharing. The chapter also discusses the mechanisms through which cooperation support exists despite widespread distrust of the Nigeria Police Force among Lagosians.

This chapter presents the results of a survey experiment testing cooperation interventions in Baltimore. It describes existing efforts in the city to promote cooperation with the police and how police rely on information from witnesses. The survey experiment entails respondents viewing and responding to a professionally produced fictional news report of a shooting with experimental variations to test the various interventions. The results show police encouraging cooperators to call an anonymous tip line (as opposed to a non-anonymous line) as well as creating awareness of cooperation norms both increase information sharing. The police commander portrayed in the news report being the same race as the respondent does not change the amount information that they are willing to share. The chapter also discusses the mechanisms of how support for cooperation exists in Baltimore despite distrust of the police.

This chapter theorizes how interventions employed by police and community safety advocates might promote cooperation. The evaluation focuses on two interventions that plausibly reverse cycles of silence: facilitating cooperator anonymity to reduce the risk involved in information sharing and creating awareness of support for cooperation to strengthen the perceived norms favoring information sharing. Given that these interventions do not address distrust in the police, which places a ceiling on cooperation support, the evaluation also includes the trust-based intervention of exposing citizens to police officers of the same race or ethnicity. The chapter concludes with enumerating principles that should be considered when evaluating the appropriateness of implementing interventions to promote cooperation.

The Introduction previews cycles of silence theory, which seeks to explain how criminal groups constrain citizen cooperation with the police. The Introduction focuses on laying out the book’s central contributions. Theoretically, the book provides a new explanation for how criminal groups prevent cooperation with the police, highlighting the role of their violence in suppressing perceived norms favoring cooperation. The theory speaks to the political science literatures on state-building, political conflict, and criminal governance as well as literatures from other social science disciplines including criminology. Methodologically, the study bridges research divides between the Global North and Global South by testing the theory in both regions. The study also employs realistic survey experiments including a virtual reality–based survey experiment. Finally, the Introduction puts the study into perspective: While the book’s focus may be centered around the effect of violence, the violence should not be interpreted as a defining feature of communities that endure criminal groups.