Proceedings of the National Academy of Sciences

The US government maintains that local sanctuary policies prevent deportations of violent criminals and increase crime. This report tests those claims by combining Immigration and Customs Enforcement (ICE) deportation data and Federal Bureau of Investigation (FBI) crime data with data on the implementation dates of sanctuary policies between 2010 and 2015. Sanctuary policies reduced deportations of people who were fingerprinted by states or counties by about one third. Those policies also changed the composition of deportations, reducing deportations of people with no criminal convictions by half—without affecting deportations of people with violent convictions. Sanctuary policies also had no detectable effect on crime rates. These findings suggest that sanctuary policies, although effective at reducing deportations, do not threaten public safety.