Prisoners spend 23.5 hours a day locked in their cells, with a brief, daily 30-minute window for exercise or religious activities in a central hallway.

Under U.S. immigration law, a country such as El Salvador can accept someone deported from the U.S. who isn’t a citizen of that country if the person’s homeland refuses to accept them, says Theresa Cardinal Brown, a former homeland security official under the administrations of Presidents George W. Bush and Barack Obama.