Several months ago, as a federal judge worked through a docket of smuggling cases in the bustling border city of Laredo, Texas, three people were escorted into the courtroom.
Because they were undocumented immigrants, the judge explained, they would be sent to jail. But they were not being charged with a crime. Instead, they would be compelled to testify against the people accused of helping them enter the United States.
The hearing took less than five minutes. The immigrants never spoke, not to ask questions or explain why they had made the illegal journey across the Rio Grande. They were then taken to jail, where they joined a long list of people — nearly 104,000 since 2003 — detained as so-called material witnesses in federal criminal proceedings.
While the law allowing the detention of witnesses in criminal cases dates back to George Washington’s presidency, its modern use has been most prevalent along the Mexican border as successive administrations have prioritized the prosecution of human-smuggling cases, according to an analysis by The New York Times of U.S. Marshals Service data obtained through a public records request.
The annual number of detainees first spiked during the George W. Bush administration, peaked at more than 8,500 during Donald J. Trump’s presidency, dipped with the onset of the pandemic and then rebounded last year under President Biden, with nearly 5,000 people jailed, the data show. Detentions in the first four months of 2023 were up 30 percent compared with last year.