What empirical evidence links local‑federal immigration cooperation to changes in local crime rates?
Executive summary
Empirical studies offer mixed but consistent patterns: formal cooperation between local police and federal immigration enforcement (programs like 287(g) and Secure Communities) is associated in several studies with worse community policing outcomes and sometimes higher measured crime, while sanctuary or pro‑immigrant policies tend to be associated with equal or lower violent crime in multiple analyses [1][2][3]. The causal channel most often invoked by researchers is not that immigrants are inherently more criminal, but that enforcement‑cooperation alters reporting, trust, and local policing capacity—effects observable in a range of quasi‑experimental and survey studies [4][5][6].
1. Quasi‑experimental and aggregate studies: what the numbers show
Panel and difference‑in‑differences analyses that track jurisdictions before and after adoption of federal‑local programs or sanctuary policies find heterogeneous effects: some papers link increased local cooperation with DHS/ICE to rises in reported crime or reductions in reporting, while others find no increase and some even find declines in violent crime where sanctuary protections exist [1][2][3]. National reviews and meta‑analyses summarized by policy institutions conclude that immigration overall is not associated with higher crime and that sanctuary policies have, at minimum, no systematic crime‑increasing effect—and some studies estimate cost savings from reduced violent victimization where trust is improved [7][8][3].
2. Mechanisms identified by researchers: trust, reporting, and policing capacity
Scholars consistently point to three mechanisms linking local‑federal cooperation to measured crime outcomes: erosion of trust that reduces immigrant victims’ and witnesses’ willingness to report crimes; diversion of local police resources toward immigration tasks; and community disruptions that can alter social control and economic life—each mechanism has been documented in empirical work and police surveys [1][4][5]. For example, research on Secure Communities and 287(g) finds increases in detentions that coincided with declines in Hispanic victims’ reporting and strained police–community relations, a dynamic plausibly producing higher unreported crime even if offender behavior did not change [4][5].
3. Mixed findings, data limits, and methodological caveats
The literature’s heterogeneity partly reflects data challenges: studies rely on different crime measures (FBI/UCR, NCVS, local records), uneven coding of policy timing and scope, and potential selection bias where jurisdictions that adopt or reject cooperation differ systematically [1][2]. National Academy and other reviews note sanctuary policies did not prevent deportations of people with violent convictions and emphasize that jurisdictions vary in how they implement “cooperation,” limiting broad generalizations [3]. Some critics argue local enforcement has no effect on cooperation with police, a position advanced by think tanks and contested by police foundation and academic surveys pointing the other way [5].
4. Political stakes, agendas, and how they shape interpretation
The debate is politically charged: advocacy groups and academic centers emphasize evidence that limiting cooperation improves trust and lowers victimization and fiscal costs, while enforcement‑focused organizations and some policymakers emphasize potential threats to public safety and selective cases of violent criminality—both sides selectively foreground studies that support their policy preferences [8][5]. Methodological choices—choice of crime data, the definition of “sanctuary,” and whether to measure reported versus actual victimization—have clear normative implications and are exploited by actors aiming to justify or oppose federal‑local partnerships [1][3].
5. Bottom line for policymakers and researchers
Empirical evidence does not support a simple claim that local‑federal immigration cooperation reduces crime; instead, multiple studies document that cooperation can undermine community trust and reporting and in several jurisdictions correlate with higher measured crime, while sanctuary‑oriented policies generally show no increase and sometimes reductions in violent crime—yet results vary by context and measurement [1][2][3]. Because causal pathways hinge on reporting behavior and local implementation, further research using victimization surveys, careful policy timing, and measures of police capacity is needed before sweeping national prescriptions can be justified [4][6].