On a rainy Monday morning in April, more than a hundred sheriffs, doctors, nurses, and jail guards from around the country sat in a ballroom on the outskirts of Nashville, sipping on coffees and listening to Daniel Potenza, a psychiatrist from New Hampshire, describe one of their most vexing problems: treating schizophrenia.

The conference, on medical care inside America's jails and prisons, had been put on by an organization that sets standards for treatment in correctional facilities. Potenza paced the stage, talking animatedly about a national mental-health epidemic that had burdened jails and prisons. He flipped to a presentation slide showing that nearly half of all inmates diagnosed with schizophrenia were "non-adherent," meaning that they weren't taking their daily medications as prescribed.