Warriors and Vigilantes as Police Officers: Evidence from a field experiment with body-cameras in Rio de Janeiro

By Beatriz Magaloni, Vanessa Melo, and Gustavo Robles  

We present the first randomized experiment on police body-cameras in a high-violence setting: Brazil. Camera assignment -regardless of whether police turned it on -reduced stop-and-searches and other forms of potentially aggressive interactions with civilians. Cameras also produced a strong de-policing effect, where police wearing cameras were significantly less likely to engage in any form of activity, including responding to requests of help. These changes in police behavior took place even when most officers disobeyed the protocol that required them to turn their cameras on when interacting with civilians. To address this problem, we randomly assigned cameras to supervisors during part of the study. When officers’ supervisors wore a camera, policing activities and camera usage increased. Police surveys, interviews and focus groups strengthen the finding that technological advances can only have a limited impact in so far an organizational culture that perpetuates lack of compliance with internal protocols and violence persists.

Stanford, CA: Stanford University, Poverty, Violence and Governance Lab (PoVgov), Working Paper, 2020. 38p.