Controversial police use-of-force incidents have eroded police legitimacy, and body-worn cameras (BWCs) have received extensive attention as a key reform. In the first chapter, I study the causal effects of BWCs on the use of force and law enforcement outcomes. Previous studies that randomized BWC deployment at the officer level within a single agency faced empirical challenges as (1) the control group officers are also indirectly affected by BWCs due to interactions with the treatment group officers (spillover), (2) there may be fundamental differences between agencies that agree to be researched and agencies that do not (site-selection bias), and (3) researchers could not directly examine agency-wide variables such as crime rates and public opinion. I overcome these limitations by conducting the first nationwide study of BWCs across more than 1,000 agencies in the US. I find that BWCs lead to substantial decreases in the use of force, both against whites and minorities. Nationwide, they reduce police-involved homicides by 58%. In contrast to previous studies on police accountability, I find no evidence of an association between police oversight through BWCs and reduction in policing efforts. By examining social media usage from Twitter, I find that BWC adoption has improved public opinion toward the police. These findings imply that BWCs can be an important tool for improving police accountability without sacrificing policing capabilities. In the second chapter, I include my work from another related line of my research that aims to understand of bureaucrats’ incentives and their decision-making. Police agencies, like other public bureaucracies, have rigid promotion structure. Combining the rigid structure based on exam or tenure with one based on merit may incentivize better police behavior or retain officers. In the Chicago Police Department, eligibility requirement in service length expedited the first promotion opportunity to officers with enough tenure by seven years relative to officers with slightly less tenure who are otherwise similar. I use this discontinuity in promotion chance to examine the effects of promotion opportunities on performance and career decisions. Overall, I find that the promotion opportunity led to less police misconducts, while I do not find evidence of changes in arrest performance or retention. I also find that it encouraged officers to invest in their career capital by joining specialized units, where promotion occurs more frequently. The results suggest a more flexible promotion policy based on merit by an evaluation board could be used to complement rigid promotion structures to improve bureaucratic behavior.