How do outcomes (crime, trust in police, deportation rates) compare between declared sanctuary cities and similar non‑sanctuary cities?

1. How crime compares: null effects and some lower‑crime signals

Multiple difference‑in‑differences and county‑level studies report no detectable increase in violent or property crime after sanctuary policies are adopted, and several analyses even find lower crime rates in sanctuary counties relative to matched non‑sanctuary places ^{[1] [3] [4]}; policy reviews and advocacy summaries likewise conclude that sanctuary measures “did not affect crime rates” or in some samples correspond with fewer crimes per 10,000 people ^{[2] [5]}.

2. Deportation outcomes: fewer removals overall, but violent offenders still leave at similar rates

Empirical work combining ICE records with crime data shows sanctuary policies reduce deportations of people without criminal convictions and substantially lower total deportation counts in affected counties, while deportations of those with violent convictions show little or no decline, indicating targeted public‑safety removals continue despite sanctuary rules ^{[1] [2] [6]}.

3. Trust in police: theory, qualitative evidence, and measured impacts

A central argument for sanctuary policies is that limiting local cooperation with federal immigration enforcement builds trust so immigrants report crimes and cooperate with investigations; law‑enforcement leaders and some studies frame this as a “spiral of trust” that improves public safety, and policy statements from police chiefs and advocacy groups echo that rationale, though much of the evidence on trust is inferential or qualitative rather than causal ^{[7] [5] [8]}.

4. Competing interpretations and methodological caveats

Scholars caution that cross‑sectional correlations (sanctuary cities having lower poverty, higher incomes, and lower crime) can reflect selection: cities that adopt sanctuary policies may already differ in ways that predict safer outcomes, and causal inference hinges on timing, controls, and matching strategies—papers using different methods sometimes reach different nuances, and critics argue sanctuary policies could lower formal sanctions which theoretically might alter incentives ^{[9] [10] [4]}.

5. What federal claims and local realities disagree about

Federal rhetoric has repeatedly claimed sanctuary policies prevent removal of violent criminals and increase crime; rigorous analyses that link ICE deportation records to local crime data dispute those broad claims, showing instead reductions in nonviolent deportations without measurable increases in crime—this divergence reflects differing agendas: federal enforcement authorities emphasize immigration control, while local jurisdictions emphasize community policing and public‑safety cooperation ^{[1] [6] [11]}.

6. Where evidence is thin and what researchers still want to know

The literature is strong on short‑to‑medium run county‑level patterns between 2010–2015 and in studies through the early 2020s, but gaps remain: long‑term causal channels for trust, heterogeneous impacts in very small jurisdictions, and the effects of layered state laws or federal crackdowns are less well quantified; several authors explicitly call for more work to disentangle selection from policy effects and to measure trust and reporting behavior directly ^{[4] [3]}.

7. Bottom line for policymakers and the public

Taken together, peer‑reviewed analyses and policy research consistently undercut the simple political claim that sanctuary policies cause more crime: they reduce deportations of nonviolent people, do not raise violent or property crime in the studied samples, and plausibly improve police‑community cooperation, although methodological caveats and political incentives on all sides mean continued scrutiny and better data are warranted ^{[1] [2] [7]}.