“Sanctuary-city policies make communities less safe.”

• Mechanically, sanctuary policies do reduce interior immigration enforcement: a peer-reviewed PNAS study found sanctuary policies cut deportations by roughly a third, meaning some removable non-citizens — including a subset with criminal convictions — remain in the community rather than being transferred to ICE.
• ICE detainers are sometimes declined for individuals who later commit serious crimes; widely publicized cases (e.g., the 2015 San Francisco killing of Kathryn Steinle by a man released despite an ICE detainer) demonstrate that the policy can have identifiable individual-level public-safety costs, even if aggregate crime rates do not move.
• Law-enforcement officials and DHS/ICE leadership have argued that releasing detainer subjects into the street rather than into ICE custody is more dangerous for officers and the public than a controlled jail transfer; this operational argument is not refuted by aggregate crime statistics.
• Studies finding 'no increase' or 'lower crime' in sanctuary jurisdictions are observational and face selection problems — sanctuary jurisdictions are disproportionately large, diverse, economically dynamic cities and counties with different baseline crime trends — so critics argue the null findings are not clean causal estimates.

• The same PNAS study that found sanctuary policies reduce deportations found no detectable effect on crime rates (including violent crime), directly undercutting the claim that reduced enforcement translates into more victimization.
• Analysis of FBI and ACS data comparing sanctuary and non-sanctuary counties (Tom Wong, 2017) found sanctuary counties had, on average, roughly 35 fewer crimes per 100,000 people than comparable non-sanctuary counties, along with higher median household income and lower poverty and unemployment.
• Peer-reviewed work on sanctuary city policies and city-level violence (Martínez-Schuldt & Martínez) found no increase in violent crime and some evidence of reductions in robbery in cities with large Latino populations, consistent with a trust/reporting mechanism.
• The underlying premise — that immigrants, including the undocumented, are unusually crime-prone — is not supported: the National Academies' comprehensive review and a large body of criminology (Ousey & Kubrin's review of decades of studies) find immigration is associated with no increase or a decrease in crime, and immigrants are incarcerated at lower rates than native-born Americans.
• There is a credible safety mechanism running the other way: aggressive local entanglement with immigration enforcement (287(g), Secure Communities) is associated with reduced crime reporting and cooperation by immigrant victims and witnesses, which police chiefs' organizations say impairs investigations.
• Evaluations of Secure Communities — the enforcement program sanctuary policies partially opt out of — found that it did not reduce crime rates, weakening the inference that limiting it must increase crime.
• No peer-reviewed study has been produced showing a statistically robust increase in crime caused by sanctuary policies; the claim rests largely on anecdotes and advocacy reports rather than systematic evidence.

85/100 — the lab’s own confidence in the score above, not a second reading of the claim.

Proceedings of the National Academy of Sciences (Hausman 2020, 'Sanctuary policies reduce deportations without increasing crime')journal · 95 · Center for American Progress (Tom K. Wong, 2017)other · 60 · National Academies of Sciences, Engineering, and Medicineedu · 95 · Annual Review of Criminology (Ousey & Kubrin, 'Immigration and Crime: Assessing a Contentious Issue')journal · 92 · The Marshall Project / New York Timesnews · 82 · FactCheck.orgfactcheck · 88 · Congressional Research Service, 'Sanctuary Jurisdictions: Federal, State, and Local Policies and Related Litigation'gov · 93 · U.S. Immigration and Customs Enforcement (detainer policy, agency position)gov · 70

• There is a plausible case-level mechanism: if a jail declines an ICE detainer and releases a person who otherwise might have been transferred to immigration custody, that person can remain in the community and may reoffend. ICE annual reports document declined-detainer concerns and removals/arrests involving people with criminal convictions, although these reports do not prove sanctuary policies raise overall crime rates.
• High-profile incidents support the possibility of individual failures. In the Kate Steinle case, San Francisco had released an undocumented immigrant after a local case was dropped despite a federal immigration request; he later fatally shot Steinle. This shows how limits on honoring detainers can be involved in specific public-safety tragedies, though it does not establish a general citywide crime effect.
• Some law-enforcement and immigration-enforcement officials argue sanctuary policies make custody transfers harder, require ICE to make arrests in the community rather than jails, and can leave more opportunity for absconding or reoffending. This is a coherent operational argument, but the stronger available evidence is mostly anecdotal or administrative rather than causal population-level evidence.

• Peer-reviewed research generally does not find that sanctuary policies increase crime. A study in Urban Affairs Review, “The Politics of Refuge: Sanctuary Cities, Crime, and Undocumented Immigration,” found no statistically meaningful increase in violent crime, property crime, or rape associated with sanctuary policies.
• Another peer-reviewed study in Justice Quarterly, “Sanctuary Policies and City-Level Incidents of Violence, 1990 to 2010,” found no evidence that sanctuary policies increased violence; if anything, sanctuary policies were associated with lower robbery rates in some models.
• FactCheck.org reviewed claims that sanctuary jurisdictions “breed crime” and found the cited statistics were misleading because they relied on raw crime totals in large cities rather than crime rates or causal evidence; experts told FactCheck.org there was no clear evidence sanctuary policies increase crime.
• The claim is phrased categorically—“make communities less safe”—but the best evidence distinguishes between anecdotal risks from individual releases and overall community safety. The broader empirical record does not support a general causal claim that sanctuary-city policies make communities more dangerous.

84/100 — the lab’s own confidence in the score above, not a second reading of the claim.

Urban Affairs Review / SAGE Journalsjournal · 92 · Justice Quarterly / Taylor & Francisjournal · 92 · U.S. Immigration and Customs Enforcementgov · 78 · CNNnews · 74

• Opponents of sanctuary policies argue that by refusing to honor Immigration and Customs Enforcement (ICE) detainers, local authorities are forced to release undocumented immigrants who have been arrested for crimes back into the community, providing them opportunities to reoffend.
• Federal agencies, including ICE and the Department of Homeland Security under various administrations, have publicly stated that sanctuary policies hinder federal law enforcement efforts and provide safe havens for criminal organizations like transnational gangs.
• Advocates for the claim frequently point to high-profile anecdotal tragedies, such as the 2015 killing of Kathryn Steinle in San Francisco by an undocumented immigrant who had been released from local custody despite an ICE detainer, as proof that non-cooperation policies cost lives.

• Extensive empirical research in criminology and sociology consistently demonstrates that sanctuary policies do not increase crime. A comprehensive 2020 study published in the Proceedings of the National Academy of Sciences (PNAS) found that while sanctuary policies significantly reduce deportations, they have no detectable effect on crime rates.
• Local law enforcement agencies in sanctuary jurisdictions often argue that these policies actively improve public safety. When undocumented residents do not fear that interacting with local police will lead to deportation, they are more likely to report crimes, serve as witnesses, and cooperate with investigations.
• A widely cited 2017 statistical analysis by the Center for American Progress found that there are actually 35.5 fewer violent crimes committed per 10,000 people in sanctuary counties compared to non-sanctuary counties, alongside stronger economic indicators.
• Independent fact-checkers have repeatedly analyzed uniform crime data and debunked claims by politicians that sanctuary cities harbor higher violent crime rates than jurisdictions that fully cooperate with ICE.

95/100 — the lab’s own confidence in the score above, not a second reading of the claim.

Proceedings of the National Academy of Sciences (PNAS)journal · 95 · Center for American Progressother · 75 · The Heritage Foundationother · 60

• Some analyses report higher crime in particular sanctuary jurisdictions or find that sanctuary policies do not reduce crime; this can support a narrow concern that the policies may fail to improve safety. However, the cited research does not establish that sanctuary policies make communities less safe.
• Sanctuary-city definitions vary substantially, and comparisons can be confounded by differences in population, urbanization, poverty, policing, and reporting practices. PolitiFact found that no definitive nationwide measurement establishes that sanctuary cities are safer or less safe. [2]

• A peer-reviewed study of sanctuary policies found no statistically discernible difference in violent crime, rape, or property-crime rates and concluded that the policies had no effect on crime rates. [3]
• Additional research summarized by PolitiFact found no statistically significant effect of sanctuary policies on crime, including violent, property, and rape offenses. [1][7]
• A later academic analysis reported that sanctuary policies did not increase crime and found weaker evidence of reduced property crime. [4]
• Research summarized by PolitiFact found that sanctuary counties had lower crime rates than comparable non-sanctuary counties, though such comparisons do not by themselves prove that sanctuary policies caused the difference. [1][8]
• Some research indicates that cooperation between immigrant communities and law enforcement can increase crime reporting and may be associated with lower crime, suggesting that limiting local involvement in federal immigration enforcement does not inherently reduce public safety. [7]
• Sanctuary policies generally concern limits on local cooperation with federal immigration enforcement; they do not ordinarily require police to release people charged with crimes. [6]

88/100 — the lab’s own confidence in the score above, not a second reading of the claim.

PolitiFactfactcheck · 93 · PolitiFactfactcheck · 93 · PolitiFactfactcheck · 93 · Cato Institute Center for Growth and Opportunityother · 78 · PolitiFactfactcheck · 93 · PolitiFactfactcheck · 93 · Urban Affairs Reviewjournal · 84 · Illinois Wesleyan Universityedu · 72

• High-profile incidents in which undocumented immigrants with prior criminal records and outstanding ICE detainers were released by sanctuary jurisdictions and later committed violent crimes (e.g., the 2015 Kate Steinle killing in San Francisco).
• ICE and DHS reports documenting that individuals released despite detainers were later arrested for additional offenses including homicide, assault, and sexual crimes.
• Analyses from restriction-oriented groups reporting correlations between sanctuary policies and certain crime metrics in selected jurisdictions.

• Texas conviction data (which records immigration status) and multiple analyses showing undocumented immigrants have lower arrest and conviction rates than native-born citizens for homicide and most other crimes.
• Peer-reviewed and think-tank studies finding no statistically significant increase in overall crime rates after cities adopt sanctuary policies; some find lower rates after demographic controls.
• Law-enforcement arguments that limiting civil-immigration cooperation increases crime reporting and witness cooperation in immigrant communities, potentially improving net public safety.
• Fact-checkers have repeatedly found insufficient evidence that sanctuary cities as a class are less safe or experience crime spikes attributable to the policies.

64/100 — the lab’s own confidence in the score above, not a second reading of the claim.

The New York Timesnews · 82 · Cato Instituteother · 76 · Center for Immigration Studiesother · 52