What does the National Academy of Sciences/PNAS research say in detail about sanctuary policies and violent crime/deportations?

1. What the PNAS study measured and how

Hausman combines ICE administrative deportation records with FBI Uniform Crime Report data and county-level information on the timing of sanctuary-policy adoption to run event-study and difference-in-differences analyses focused on 2010–2015, using “local-fingerprint” removals as the primary deportation outcome and testing crime trends before and after policy adoption ^{[4] [2]}.

2. The headline deportation effects: fewer removals overall

The paper’s central quantitative finding is that sanctuary policies reduced deportations of people fingerprinted by local authorities by roughly one-third relative to counterfactual trends in those counties between 2010 and 2015, an effect the author interprets as meaningful at scale ^{[5] [1]}.

3. Composition matters: non-criminals vs. violent convictions

A key nuance is compositional change: deportations of people with no criminal convictions fell by more than half under sanctuary policies, whereas deportations of people with violent convictions showed no consistent decline—Hausman stresses that deportations of violent offenders were relatively rare and often governed by policy exceptions, which helps explain why sanctuary status did not appear to shield violent offenders from removal ^{[2] [3]}.

4. Public-safety finding: no detectable increase in violent crime

Contrary to federal claims that sanctuary policies raise crime, the PNAS analysis finds no detectable increase in violent or property crime rates in jurisdictions that enacted sanctuary measures during the study window; the author situates this null effect alongside other recent county- and city-level work that similarly reports little or no positive association between sanctuary policies and violent crime ^{[1] [6] [7]}.

5. Scale estimates, exceptions, and real-world interpretation

The paper provides scale context—reporting, for example, an estimated prevention of roughly 22,300 deportations nationwide between 2013 and 2015, including some thousands of non-convicted individuals—while noting many sanctuary policies explicitly exempt people accused or convicted of serious violent crimes, a statutory and operational detail that helps reconcile the reduction in overall removals with the unchanged rate for violent convictions ^{[3] [8]}.

6. Limits, alternative evidence, and ongoing debate

Hausman is explicit about limits: the analysis covers 2010–2015 and relies on administrative categorizations (local-fingerprint removals, ICE conviction categories) that make violent-conviction deportations a low-frequency outcome and therefore harder to measure precisely; other scholars and policy advocates point to complementary studies that find null or sometimes negative associations between restrictive immigration enforcement and crime, while critics argue different datasets, definitions, or later policy regimes (post-2015) could yield different results—those possibilities are outside the PNAS paper’s empirical window ^{[2] [6] [9]}.

7. Bottom line for policy and reporting

The PNAS/NAS-backed finding is straightforward: within its 2010–2015 county-level design, sanctuary policies clearly reduced deportations overall—especially of people without convictions—without producing measurable increases in violent crime, and they did not appear to block the deportation of people with violent convictions; however, the study’s temporal scope, the rarity of violent-deportation events, and policy heterogeneity mean the results should be read as strong evidence for null public-safety harms in that period rather than as a universal, immutable rule for every jurisdiction or later policy change ^{[1] [2] [3]}.