Despite a steep decline in crime, admissions to local jails have nearly doubled nationwide over the last 30 years. Attempting to explain the paradox, a new report from the Vera Institute of Justice concludes that jails are grossly misused. Unlike federal and state prisons, jails are meant to hold people who have not been convicted of crimes but who are deemed too dangerous to release pending trial, or those who are likely to flee before a trial can begin. But that’s no longer the best description of what jails do, or who’s in jail, the report says.

Sixty percent of jail detainees are too poor to pay even the minimum bail required for the minor crimes they’re accused of — most often traffic, drug, property or public order offenses, the report says. Almost always one or more social problems are intertwined: substance abuse, chronic poverty, failure in school, homelessness and, most notably, mental illness.

For many people with mental disorders, jail becomes a kind of revolving-door lifestyle. Over time, a relatively few people — arrested again and again — take up a disproportionate amount of the jail space. In Chicago, over a five-year span, 20 percent of inmates filled half of the jail cells. In New York, over a similar period, 473 people were sent to jail 18 times or more.

The emerging picture is one of local jails becoming modern-day debtors prisons and places to stash the mentally ill. Hennepin County Sheriff Rich Stanek estimates that 30 percent of the 37,000 people locked up every year in Minnesota’s largest local jail have serious mental problems. “Obviously, jail isn’t the best place for treating mental disorders,” he said.

Deinstitutionalization, while a noble undertaking, explains part of the problem. The mass closing of mental hospitals in recent decades has left side effects for a segment of patients and for the public. A few people who might otherwise have been institutionalized have committed violent acts — most notably mass shootings in schools or at work places or at public meetings.

A larger segment has simply been dumped on the sidewalks of major cities, including Minneapolis and St. Paul. Many of those people divide their time between jail and the street with far too little attention to their mental health.

Locally, a new psychological evaluation team stationed within the Hennepin County jail has helped authorities to deal more promptly and expertly with some of those cases, Stanek said. And a new Minnesota law forbidding jails to hold mentally ill inmates charged with a crime for more than 48 hours has helped the situation in jails throughout the state. Still, a huge problem remains: Where to send inmates who need mental health treatment?

Too often it’s back on the street with a sheet of paper suggesting where they might go to get help, according to state Sen. Barb Goodwin, DFL-Columbia Heights. But that doesn’t work with this particular population, she said. What’s needed is an option for police to take unruly and troubled people to psychiatric crisis centers rather than to jail. There are 500 such diversion programs across the country, Goodwin said, but none in Minnesota. Indeed, Minnesota ranks near the bottom in the per-capita supply of psychiatric beds.

Rather than worry so much about stigmatizing patients, the state should be focused on providing treatment. Minnesota legislators should consider Goodwin’s proposal (Senate File 141) to offer grants to counties for jail diversion programs. The need is particularly critical in rural counties where mental health facilities — when available — are sometimes more than 100 miles away.

Relying on jails only compounds the problem. As the Vera report concludes: “The consequences are corrosive and costly for everyone because no matter how disadvantaged people are when they enter jail, they are likely to emerge with their lives further destabilized and, therefore, less able to be healthy, contributing members of society.”