One of the great scandals of the American criminal justice system is that on any given day, there are about half a million people locked up in jail who have not been convicted of any crime. They’re behind bars because they’ve been arrested and are awaiting hearings or trial dates. Some of them are there because they’ve been deemed dangerous, or because a court determined that they could not be counted on to show up for their next appearance. But in many cases, they are in jail because only they couldn’t afford to pay the bail set for them by a judge.

There are extreme stories about “unconvicted” people spending years in jail before their cases are resolved. Kalief Browder spent more than 1,000 days on Rikers Island, only to have the charges against him dropped. The experience so traumatized Browder, who was profiled in the New Yorker last October, that his suicide earlier this month has come to symbolize the cruel folly of forcing people who pose no threat to public safety, and are presumptively innocent, to sit endlessly in jail waiting for their number to be called. But even those who are detained for just a few days often suffer collateral consequences in the form of lost wages, disruptions to their family life, and negative effects on their physical and mental health.

The growing realization that America’s jail system is broken has spurred some intriguing reform efforts. The MacArthur Foundation recently gave out grants to 20 jurisdictions where officials have committed to reducing their reliance on jail and addressing racial disparities in jails. According to the Vera Institute of Justice, which is working with MacArthur on the initiative, blacks and Latinos make up 51 percent of the U.S. jail population, even though they represent only 30 percent of the general population.

Among the cities participating in the MacArthur program is New Orleans, a place that just 10 years ago had a higher percentage of its population in jail than any other American city. According to a report published this week by the Data Center, an independent nonprofit that produces research on issues like disaster recovery, workforce development, and housing in Greater New Orleans, the city has since made great strides that could make it into a national model for reform.

Before Hurricane Katrina decimated New Orleans in 2005, the rate at which the city incarcerated people in Orleans Parish Prison, its jail complex, stood at five times the national average. From 1981 until the arrival of the storm, the jail population grew from 2,300 inmates to about 6,300. A report by the nonprofit Metropolitan Crime Commission found that close to half of the people who did time in the OPP between 2003 and 2004 did not end up getting prosecuted, and just 7 percent ultimately received prison sentences. Of all the arrests that resulted in jail time, 86 percent were the result of nonviolent charges.

It was a grim situation. But over the past 10 years, New Orleans has reversed course. The Data Center report, which was co-written by two policy experts from the Vera Institute as well as retired Orleans Parish Judge Calvin Johnson, describes how a reform movement, sparked by the devastating damage Hurricane Katrina did to the OPP facility, has reduced the city’s daily jail population by 67 percent, from 6,000 before the storm to fewer than 1,900 in April.

“The storm and its aftermath required the rebuilding of the entire jail complex, just physically speaking,” said Jon Wool, one of the Vera experts, adding that attention became focused on the system’s deeper problems when it was revealed that some inmates had been abandoned in the OPP as it filled with floodwater before finally being evacuated.

Ironically, the daunting task of rebuilding the jail after Katrina had a positive effect, in that it forced city officials to take stock of how they had been using the jail system up to that point.

“One of the things you have to understand about us—that is, New Orleanians—is how late we have been coming to the realization that we have to actually manage, in some fashion, the criminal justice system,” said Judge Johnson.

But for the storm, we didn’t have the thing that caused us to really look at what it was that we were doing. … We were not thinking about it in terms of how many people get arrested, what they get arrested for, how many people we have in jail, how long they stay in jail, how they come into the court system, what happens when they come into the court system, and what happens as a result of that—we weren’t really thinking about any of those things. The storm was the precursor for everything that’s come since.

Initially, the post-Katrina plan was to just rebuild the jail complex more or less as it was before—with a total capacity of 5,832 beds—and to use FEMA funds to do so. But when the plan was made public, local activists started working to convince officials in the mayor’s office and on the City Council that instead of just rebuilding the jail, they had an opportunity to do something about the systemic flaws that had for so long been plaguing the local justice system. After the activists won support from several key officials, the mayor agreed to convene a working group to investigate the issue. In November 2010 that group came back with a proposal ambitious in its limitations: The New Orleans jail system would be capped at just 1,438 beds. “The decision was made to rethink and not simply rebuild,” said Wool.

The cornerstone of the population reduction plan was the introduction of a system for deciding who should and shouldn’t be in jail while awaiting a disposition of his or her case. This system called for the introduction of what’s known as “pretrial risk assessment,” which operates on the principle that the only people who really need to be held in custody before they’ve been convicted are those who are likely to commit more crime or flee if given the chance. Before this, New Orleans had no such system, according to the Data Center report, and as a result, it was virtually unheard-of for a defendant to be spared pretrial detention without having to pay bail.

Having that hard limit of 1,438 beds in place was crucial, according to Wool. “There’s absolutely no underestimating how important it is to constrain demand for jail beds by restricting supply,” he said. By capping the number of available beds, the City Council sent a signal to everyone in the system—police, prosecutors, judges—that jail was a resource that was not to be overused.

Still, actually getting the city’s jail population down by two-thirds required a few separate initiatives. One was changing the funding structure for the jail. In the old system, the facility received a per diem from the city for every inmate and was therefore directly incentivized to maintain a high population. Another involved the police: Thanks to a series of ordinances enacted in 2008 and 2010, simple marijuana possession—along with other nonviolent municipal offenses—started being punished with court summonses instead of jail time, meaning people accused of minor crimes could go on with their lives as long as they showed up to their court date. According to the Data Center report, prior to this shift in policy, 70 percent of people charged with nonviolent municipal offenses were being arrested and sent to jail for as long as 45 days, the state limit on how long someone suspected of a misdemeanor can be held captive before being formally charged. Since the policy change, the Data Center reports, the numbers have flipped, with officers writing 70 percent of nonviolent offenders summonses instead.

Interestingly, pretrial risk assessment, despite being at the center of the city’s plan for reducing the jail population, has been only modestly successful thus far: According to the Data Center report, only 10 percent of low- and low-moderate-risk defendants are being released without bail. While that is an improvement compared with the pre-Katrina years, when virtually all defendants were asked to pay bail, Judge Johnson said that a lot of his former colleagues are still demanding money from defendants at pretrial hearings in exchange for their freedom. Getting those judges to switch to a risk-based model, he said, is going to require a serious culture change. “I think there’s still, in the judges’ minds in New Orleans, the notion that If I approve a release and a bad thing happens—that is, the individual goes out and he does a bad thing—that will adversely affect my re-election opportunity,” Johnson said. “That thought pattern still prevails with judges.”

While Johnson and Wool both emphasize that there’s a lot more work for New Orleans to do—Wool pointed out that the city’s local incarceration rate is still double the national average—they say that the progress that has been made so far is proof of what is possible at the national level.* The city’s success is especially significant because it has been achieved in the South, a region of the United States where, according to Wool, overuse of local incarceration is a worse problem than it is in the rest of the country.

“To the extent that a Southern city makes progress in this area, it puts wind at the sails of the movement toward more appropriate use of jails nationally,” Wool said. “If they can do it here, it can be done anywhere.”

The only problem with that reasoning is that reform in New Orleans happened only because Hurricane Katrina—an extraordinary event that profoundly transformed the city—brought the overincarceration issue to the fore. Judge Johnson said other cities in America should be more proactive. “Don’t wait, America, for some kind of calamity to make you look at the reality of your justice system,” Johnson said. “It’s past time for America to truly examine what the justice system is, and from there, what it ought to be.”

*Correction, June 21, 2015: This article originally misstated the factor by which the local incarceration rate in New Orleans is larger than the national average. It is twice, not 1.5 times, as high. (Return.)