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Focusing police efforts on "hot spots" has gained acceptance among researchers and practitioners. However, little rigorous evidence exists on the comparative effectiveness of different hot spots strategies. To address this gap, we randomly assigned 83 hot spots of violence in Jacksonville, Florida, to receive either a problem-oriented policing (POP) strategy, directed-saturation patrol, or a control condition for 90 days. We then examined crime in these areas during the intervention period and a 90-day postintervention period. In sum, the use of POP was associated with a 33% reduction in "street violence" during the 90 days following the intervention. While not statistically significant, we also observed that POP was associated with other non-trivial reductions in violence and property crime during the post-intervention period. In contrast, we did not detect statistically significant crime reductions for the directed-saturation patrol group, though there were non-significant declines in crime in these areas during the intervention period. Tests for displacement or a diffusion of benefits provided indications that violence was displaced to areas near the POP locations, though some patterns in the data suggest this may have been due to the effects of POP on crime reporting by citizens in nearby areas. We conclude by discussing the study's limitations and the implications of the findings for efforts to refine hot spots policing.

The next phase of evidence-based policing requires both scholars and practitioners to move from lists of specific studies about "what works" to using that information strategically. This requires developing generalizations or principles on the nature of effective police strategies and translating the field of police evaluation research into digestible forms that can be used to alter police tactics, strategies, accountability systems, and training. In this article, we present a tool intended for such use: the Evidence-Based Policing Matrix. The Matrix is a consistently updated, research-to-practice translation tool that categorizes and visually bins all experimental and quasi-experimental research on police and crime reduction into intersections between three common dimensions of crime prevention-the nature of the target, the extent to which the strategy is proactive or reactive, and the specificity or generality of the strategy. Our mapping and visualization of 97 police evaluation studies conducted through December 31, 2009, indicate that proactive, place-based, and specific policing approaches appear much more promising in reducing crime than individual-based, reactive, and general ones. We conclude by discussing how the Matrix can be used to guide future research and facilitate the adoption of evidencebased policing.

Research Summary In this article, we provide the most comprehensive narrative review to date of the research evidence base for body‐worn cameras (BWCs). Seventy empirical studies of BWCs were examined covering the impact of cameras on officer behavior, officer perceptions, citizen behavior, citizen perceptions, police investigations, and police organizations. Although officers and citizens are generally supportive of BWC use, BWCs have not had statistically significant or consistent effects on most measures of officer and citizen behavior or citizens’ views of police. Expectations and concerns surrounding BWCs among police leaders and citizens have not yet been realized by and large in the ways anticipated by each. Additionally, despite the large growth in BWC research, there continues to be a lacuna of knowledge on the impact that BWCs have on police organizations and police–citizen relationships more generally. Policy Implications Regardless of the evidence‐base, BWCs have already rapidly diffused into law enforcement, and many agencies will continue to adopt them. Policy implications from available evidence are not clear‐cut, but most likely BWCs will not be an easy panacea for improving police performance, accountability, and relationships with citizens. To maximize the positive impacts of BWCs, police and researchers will need to give more attention to the ways and contexts (organizational and community) in which BWCs are most beneficial or harmful. They will also need to address how BWCs can be used in police training, management, and internal investigations to achieve more fundamental organizational changes with the long‐term potential to improve police performance, accountability, and legitimacy in the community.

What is the aim of this review? This Campbell systematic summarizes the evidence from 30 studies of the effects of BWCs on several officer and citizen behaviors. The majority of studies are from the United States. 1.2 | What is this review about? The last decade has been marked by the rapid adoption of BWCs by the police and a growing body of evaluation research on the technology's effects. Spurred on by high-profile officer-involved shooting incidents and protests, many citizens and community groups have supported the adoption of BWCs, hoping that this technology will deter police misconduct, better capture use-of-force events, and increase police accountability and transparency. At the same time, some police officers and community members have expressed concerns that BWCs might discourage citizens from reporting crimes or cause officers to pull back on preventative or proactive activities that may help prevent offending. This Campbell