Trump’s immigration authorities were also far more likely than their predecessors in the Obama administration to cite reasons such as “suicide risk” or “protective custody for LGBT people” as justification for sending immigrant detainees to solitary confinement. Under Trump, one out of every 200 detainees has spent at least two weeks in isolation, according to the documents.

Adam Serwer: A crime by any name

The documents used in this investigation were obtained through a half-dozen open-records requests filed separately over the past four years by The Atlantic, The New York Times, the Project on Government Oversight, the American Civil Liberties Union, and the National Immigration Justice Center. After more than a year, ICE fulfilled some of my records requests by providing thousands of pages of heavily redacted files. The agency erred, however, in its effort to conceal electronically much of the information in these records: Blacked-out portions had been digitally misformatted, making the redaction easily reversible, which in hundreds of cases revealed which detainees were being held for extended periods in solitary, as well as where and why.

Additional materials were provided to me by a whistle-blower lawyer named Ellen Gallagher, who contacted me in 2015 in response to an investigation I had co-produced for The New York Times about immigrants being put in solitary confinement. Gallagher, who has worked for more than two decades as a civil servant in the federal government on immigration and prison issues, including in the Obama and Trump administrations, said she was ready to become a whistle-blower because she was alarmed at how, despite talk of reform, severe problems persisted in how the United States was using solitary confinement. Gallagher, who also told her story to reporters with the International Consortium of Investigative Journalists, now works at Homeland Security’s Office of Inspector General as a director in the Office of Integrity and Quality Oversight.

The records obtained do not capture all cases when solitary was used, just those that triggered reporting requirements, which is supposed to happen within a few days of placement for people considered part of a vulnerable population, such as those with diagnosed mental-health conditions, or at 14 days for the general population.

From 2016 to early 2018, about 40 percent of the cases of people being placed in solitary confinement by ICE involved immigrants with mental illnesses—even though the agency’s own doctors and lawyers warn that such treatment severely worsens these illnesses.

Medical experts say that the use of solitary confinement is especially dangerous for vulnerable populations such as the mentally ill. Human-rights lawyers add that the use of the practice by ICE is particularly egregious because immigrant detainees are most often being held on civil, not criminal, charges. Consequently, they are not supposed to be punished, merely confined in order to ensure that they appear for administrative hearings.