With technology, this company turns migrants into easy prey for Trump.

At least once a week, the migrant, a former Honduran police officer living in Louisiana, took a selfie using the app, which uses facial recognition, to confirm his identity and location. By surrendering some of his privacy, he avoided detention and obtained a work permit.

In February, he received a message: he needed to report to an immigration office to have his tracking technology updated. When he arrived, federal agents were waiting. They handcuffed him and put him in a vehicle bound for a detention center, where he has remained ever since, according to his wife and Jacinta González, a program manager for the advocacy group MediaJustice, who works with the detained migrant. Both González and his wife declined to give their names for fear of jeopardizing his legal case.

The app he used was developed by Geo Group, the largest private prison operator in the United States. Over the past decade, the company has also built a lucrative side business of digital tools—ankle monitors, smartwatches, and tracking apps, among other things—to monitor migrants on behalf of the federal government.