We study criminal recidivism in Argentina by focusing on the rearrest rates of two groups: individuals released from prison and individuals released from electronic monitoring. Detainees are randomly assigned to judges, and ideological differences across judges translate into large differences in the allocation of electronic monitoring to an otherwise similar population. Using these peculiarities of the Argentine setting, we argue that there is a large, negative causal effect on criminal recidivism of treating individuals with electronic monitoring relative to prison.