How do law enforcement agencies differentiate between legal and illegal immigrant crime?
Executive summary
Law enforcement distinguishes criminal conduct from immigration status by using separate legal authorities: federal immigration agencies (ICE/CBP) enforce civil immigration laws and prosecute immigration offenses, while local police investigate crimes under state law and—depending on agreements—may cooperate with ICE through programs like 287(g) or task forces [1] [2] [3]. Research shows that shifting local police toward immigration enforcement can reduce crime reporting and community trust, while many studies find immigrants overall commit crime at equal or lower rates than U.S.-born residents [4] [5] [6].
1. Two legal tracks: criminal law versus immigration law
U.S. law separates state and federal criminal jurisdiction from immigration enforcement. ICE’s Enforcement and Removal Operations (ERO) categorizes arrests by criminal history—those with U.S. convictions, pending charges, or those with only immigration violations (e.g., overstays, reentry after removal)—and uses administrative authority to remove noncitizens even when no state criminal charge exists [1]. CBP likewise records “apprehensions” that may not equal criminal arrests, signaling a distinct administrative track for immigration status [3].
2. How agencies identify someone’s status and criminality
Border and federal agents use identity checks, criminal records, international information-sharing and risk assessments to decide detention, prosecution or release; CBP and ICE report using biographical checks and intelligence-driven targeting to separate national-security/public-safety threats from immigration-only cases [3] [1]. Available sources do not mention detailed biometric or database mechanics beyond “record checks” and “intelligence-driven” operations [1] [3].
3. Local police: cooperation, limits and choices
Local law enforcement can partner with federal immigration authorities through formal programs such as 287(g) or task forces, enabling local arrests to lead to immigration detainers or referrals to ICE [2]. Advocacy and legal groups argue that disentangling local policing from federal immigration aims preserves trust and reporting; scholarship shows sanctuary policies that limit cooperation can improve reporting and community safety [6] [4].
4. Reporting bias and the data problem
Scholars warn that enforcement policy affects crime statistics: when police enforce immigration, immigrants may avoid reporting victimization or cooperating, changing measured crime trends even if underlying behavior is constant [4]. The Cato and other policy reviews underscore the difficulty of separating undocumented from documented immigrants in many datasets, complicating comparisons of offending rates [7] [8].
5. What research finds about immigrant crime rates
Multiple research syntheses and think-tank briefs report that immigrants generally commit crimes at lower rates than native-born Americans, and some long-term studies link rising immigration with reductions in violent crime [5] [9] [6]. The National and academic literature cited in migration-policy and advocacy analyses supports that overall immigration is not associated with increased crime [5] [9].
6. Enforcement as public-safety policy: competing narratives
Federal policy documents and executive actions frame expanded immigration enforcement as a public-safety priority and call for coordination across departments to target “removable aliens” who threaten security [10]. Critics and empirical studies counter that heavy local-federal cooperation (e.g., 287(g)) can undermine policing goals by reducing community trust and diverting police resources from evidence-based crime prevention [6] [11].
7. Practical distinctions in case handling
In practice, someone arrested for a violent felony will be processed under criminal law; if they are noncitizen, ICE may place a detainer or pursue removal after criminal proceedings. By contrast, visa overstays or first-time unlawful entries are typically immigration violations handled administratively and sometimes criminally depending on statutes invoked [1] [3]. TRAC data show immigration prosecutions—especially for illegal entry—fluctuate sharply with policy priorities, demonstrating that enforcement choice affects whether matters wind up in criminal courts [12].
8. Limits of available reporting and what’s missing
Available sources explain institutional roles, trends, and research findings but do not provide granular, nationwide protocols for every agency nor full technical details on information systems used to classify noncitizens [1] [3]. They also note methodological limits: many datasets cannot reliably separate undocumented from documented immigrants, creating uncertainty in measuring offending differentials [8] [7].
9. Bottom line for policymakers and the public
Distinguishing “illegal immigrant crime” from regular criminality is both legal and operational: immigration status triggers administrative removal processes while criminal acts trigger prosecution under criminal law; cooperation between agencies is discretionary and contentious [1] [2]. Evidence cited by migration-policy researchers, the American Immigration Council and public-policy analysts shows immigrants are not driving higher crime rates, and scholars warn that mixing immigration enforcement into routine policing reduces reporting and may harm public safety [5] [9] [4] [6].