Trump Used ‘Stingrays’ to Hunt Immigrants. Now Biden Is Too.

When Milton Marin Caceres-Molina was arrested in New York for false impersonation—essentially a charge over lying to a police officer about a name or birthdate—his fingerprints showed that he had been deported to his home country of El Salvador in 2010.

But by the time authorities figured out who Caceres-Molina was, he was already gone.

Federal law enforcement officials tried to locate Caceres-Molina based on selfies he posted to Facebook. But when that effort failed, a U.S. Marshal applied for a warrant to authorize the use of a controversial technology...