Since President Joe Biden took office, the U.S. population has grown by at least 4 million more migrants who entered the United States illegally.
During last week’s debate with Biden, former President Donald Trump asserted the tally includes “millions” of criminals and mental patients — an eye-popping claim not supported by government data.
The Trump campaign ignored repeated requests to provide evidence.
“I’d love to ask him, and will, why he allowed millions of people to come in here from prisons, jails and mental institutions to come into our country and destroy our country,” Trump said early in the CNN debate.
Migration experts, including conservatives who share the ex-president’s desire to tighten border controls, say Trump’s claims are wildly exaggerated.
“In a debate like what you saw between Biden and Trump … sometimes people engage in a bit of hyperbole,” said Dan Stein, president of the Federation for American Immigration Reform, which supports restrictions in immigration.
Precise data on the number of convicted criminals and former residents of mental institutions is hard to come by. These are not statistics kept or reported by the Department of Homeland Security.
This wasn’t the first time Trump accused Biden of allowing “millions” of criminals and mental patients into the country. After he asserted it again in late May, during his New York criminal trial, Politifact called the claim “absurd.”
At a New Hampshire campaign rally last October, Trump told supporters that “they’ve allowed, I believe, 15 million people into the country from all of these different places like jails, mental institutions.”
Trump’s belief, 15 million, is implausibly high — nearly as many as the top-end estimates of the total number of people living in the country illegally.
Advocacy groups and government agencies do estimate the overall number of migrants who enter the country, and whether they get deported or turned back, or are allowed into the country to await further processing.
According to the Center for Immigration Studies, a group that supports tighter immigration policy, the number of illegal immigrants in the country has risen by 6.6 million since Biden took office in January 2021.
Republicans in Congress regularly cite a figure of 8 million illegal entries, though that doesn’t account for people who are quickly turned back at the border.
Factcheck.org, using federal data, put the figure at 4.2 million in February, counting people who either slipped into the country without getting caught since Biden took office, or who entered illegally and were then released into the country to await further proceedings.
Pew Research Center estimated that about 11 million were living in the United States in 2021. In June 2023, FAIR issued an estimate of nearly 17 million.
Stein said FAIR has no evidence of any country releasing prisoners in recent history and sending them to the United States, though he doesn’t rule out that possibility, citing the past and current presidents of Venezuela, Hugo Chávez and Nicolás Maduro.
“Why wouldn’t someone like Chávez or Maduro want to use the opportunity of our poorly regulated borders to offload the undesirables?” he said.
At a campaign event in April, Trump falsely claimed Venezuela’s crime was down 67% because its government was sending criminals into the United States. Apart from the lack of evidence about Venezuela sending criminals to the U.S. The claim vastly exaggerated the drop in crime in that country.
Migration experts say they are unaware of widespread entry into the United States by criminals and mental patients, including among migrants who crossed the border undetected. Anyone with a serious criminal record, or who appears on a terrorist watch list, would be ineligible to be released into the country to await an asylum hearing.
“There is no evidence of any such effort nor has the Trump campaign offered any proof of this allegation,” said Michelle Mittelstadt, director of communications at the nonpartisan Migration Policy Institute.
Border security and illegal immigration are among Trump’s favorite campaign topics. Building a border wall was a central promise in 2016.
“If you think of how Donald Trump got elected,” said Charis Kubrin, a criminology professor at the University of California Irvine, “immigration was sort of his claiming that he’s gonna clean up immigration and round up all these individuals and deport them back. That resonated with voters that supported him.”
Trump has taken a similar approach in 2024, highlighting attacks by people in the country illegally against innocent U.S. citizens.
“I call it Biden migrant crime,” he said during the debate.
Trump leveled the claim about “millions” of criminal immigrants repeatedly during the debate, unchallenged by CNN’s moderators or by Biden.
“We had the safest border in the history of our country. … He decided to open up our border, open up our country to people that are from prisons, people that are from mental institutions, insane asylums, terrorists,” Trump said.
Apart from criminals and mental patients, Trump also claimed at the debate that “we have the largest number of terrorists coming into our country right now.”
Encounters of people with terrorist affiliations are rare, but the number of people apprehended at the border with terrorist connections has increased in the last three years.
So far under Biden, 1,703 migrants with terrorist connection have been apprehended at the border, CBP data shows — far outpacing the 1,432 during all of Trump’s time in the White House.
Kubrin said that decades of data show that mass shootings by fellow Americans are a bigger source of concern than the relative handful of sensationalized crimes committed by people in the country illegally.
“Immigrants commit crime at a lower rate compared to their native born peers,” she said. “When there are challenges in society, we are looking for scapegoats.”
Customs and Border Patrol screens asylum-seekers for criminal records and gang affiliation, and checks names against terrorists watchlists.
From October through May — fiscal year 2024 so far — CBP has arrested 27,082 migrants at the border who had criminal records. That compares to 11,501 for fiscal year 2020, the last full year during Trump’s presidency.
Those arrested would not have been released into the country in the way Trump described, however.
For Stein, even one crime committed by someone who had no right to be in the country is one too many.
“The fact that we can grow our own criminals and we don’t really need to import them isn’t really an answer,” he said.
This article was produced by Cronkite News at the Walter Cronkite School of Journalism and Mass Communication at Arizona State University.