One crime wave, three hypotheses: using interrupted time series to examine the unintended consequences of criminal justice reform, computer tablet recording of crime and a long-term hot spots policing programme

After sustained reductions in robberies and thefts in 2016, the city of Montevideo, Uruguay, experienced a sudden increase in these crimes in late 2017. Using interrupted time series regressions, and controlling for seasonality using ARIMA models, we investigated three potential explanations for this increase: (1) the failure of a hot spots policing program to maintain crime decreases; (2) improved crime recording by police patrols using tablet computers; and (3) the change from an inquisitorial to an adversarial criminal justice procedure. We found that the hot spots policing program that began in April 2016 continued to be associated with crime reductions during 2017, that the increases observed after November 2017 were strongly associated with the new criminal justice procedure, and that tablets had a positive, albeit negligible, effect. The findings illustrate that criminal justice reforms, desirable as such reforms may be, can have unintended consequences on crime levels.