The Chicago jail and many of its 3,300 counterparts across the country have become treatment centers of last resort for people with serious mental illnesses, most arrested for non-violent crimes. And like other jails, it is awash in a tide of booking and releases that make it particularly unsuited for the task.

U.S. jails, most of whose 731,000 inmates are trying to make bail or awaiting trial, hold roughly half the number in prisons. But last year, jails booked in 11.7 million people — 19 times the number of new prison inmates. The revolving door complicates the task of screening for mental illness, managing medications, providing care and ensuring inmate safety.

"Jails are churning people," says Henry J. Steadman, a consultant to government agencies on how courts and correctional facilities deal with people with mental illnesses.

Experts have pointed to rising numbers of inmates with mental illnesses since the 1970s, after states began closing psychiatric hospitals without following through on promises to create and sustain comprehensive community treatment programs.

But as the number of those with serious mental illnesses surpasses 20 percent in some jails, many have struggled to keep up, sometimes putting inmates in jeopardy.