Bad Cop, Bad Cops: Peer Effects in Police Misconduct

We provide the first evidence of causal peer effects in police misconduct using data from about 50,000 officers and staff from London’s Metropolitan Police Service for the period 2011-2014. Previous research is limited to short-term or cross-sectional studies, which prevents inference about causality in peer misconduct. A novel aspect of our data is that it follows employees over time as they change roles and identifies their peers and their supervisors, allowing us to estimate reliable causal relationships. We use instrumental variable techniques and exploit the variation in peer misconduct that results when officers switch peer groups. We find that moving one officer with an incident of misconduct into a group of nine officers increases each of the nine officer’s personal misconduct risk by an absolute 9%