What percentage of illegal immgrants are criminals
Executive summary
Available federal and independent reporting shows that only a minority of undocumented (commonly termed “illegal”) immigrants have criminal convictions: counts of people in ICE detention indicate roughly 27–28% have convictions while long‑term incarceration of the undocumented population is much lower (around 1%); scholars and policy groups also report that immigrants—documented and undocumented—tend to have lower crime and incarceration rates than the U.S.-born population [1] [2] [3] [4].
1. What the raw detention numbers show — a minority with convictions
Records captured by detention-focused trackers and fact‑checks find that most people held by ICE at given snapshots lack a criminal conviction: TRAC reported that 48,377 of 65,735 people in ICE custody (73.6%) had no criminal conviction as of November 30, 2025, and independent fact‑checks using TRAC data put the share without convictions at about 72% in September 2025—implying roughly 27–28% with convictions among that detained population [1] [2]. These detention figures are frequently cited in public debate to support the claim that most apprehended noncitizens are not “criminal aliens,” but they reflect the characteristics of the detained population at a moment in time, not the entire unauthorized population.
2. One percent in prison — a very different metric of “criminal”
Longer‑range estimates of the undocumented population’s contact with the penal system tell a different story: research summarized by the Center for Migration Studies and Congressional sources finds that only a small share of the resident undocumented population is incarcerated — the Congressional Research Service estimated roughly 140,000 undocumented people in prison at one point, which is only slightly more than 1% of the total undocumented population—far below the rates implied by snapshots of enforcement caseloads [3].
3. Crime rates and comparative research — immigrants commit less crime
A broad academic consensus and policy analyses conclude that immigrants overall, including unauthorized immigrants, commit crimes at lower rates than the U.S.-born population; Migration Policy’s explainer cites multiple peer‑reviewed studies and state‑level data showing reduced criminality among immigrants, and a Texas study that can disaggregate by immigration status supports the finding that undocumented individuals have lower arrest and conviction rates than native‑born residents [4] [5]. The American Immigration Council similarly documents falling overall crime rates concurrent with rising immigrant shares of the population, arguing that immigration has not increased crime [6].
4. Federal sentencing and enforcement categories complicate the picture
Federal sentencing data show that many non‑U.S. citizens who are sentenced in federal courts receive immigration‑related guidelines (72.3% under immigration guidelines) and that over half had little or no prior criminal history, which underscores the fact that a large portion of federal cases involving noncitizens concern immigration violations rather than violent or serious criminality [7]. At the same time, ICE and DHS produce tallies of “noncitizens with criminal histories” on enforcement dockets—hundreds of thousands by agency counts—which officials use to argue for enforcement resources even though those counts mix offense types and include past convictions of varying severity [8].
5. Why different numbers exist — definitions and selection bias
Divergent figures stem from differing definitions (convictions vs. arrests vs. types of offenses), sample frames (people in custody or on enforcement dockets versus the whole undocumented population), and policy incentives: enforcement agencies highlight criminal‑history tallies to justify operations, whereas advocacy groups and researchers emphasize population‑level incarceration and comparative crime rates to counter narratives that immigration drives crime [9] [8] [6]. Each source has an implicit agenda—agencies justify enforcement, advocacy groups defend immigrant communities, and researchers aim for analytical clarity—so claims must be read in context.
6. Bottom line and limits of the evidence
There is no single, definitive percentage that captures “what percentage of illegal immigrants are criminals” because that depends on the metric chosen; using detention snapshots, roughly 27–28% of people in ICE custody have criminal convictions [1] [2], but population‑level incarceration is much lower (about 1% in prison at a point estimate) and broad research shows immigrants generally commit crimes at lower rates than the U.S.-born [3] [4]. The existing sources do not permit a single precise national percentage of undocumented people who are “criminals” across all definitions, and reporting limitations mean any definitive‑sounding number should be treated with caution [1] [3].