Last Monday, Judge Shira Scheindlin of the Southern District of New York, the subject of Jeffrey Toobin’s piece in last week’s issue, heard closing arguments in Floyd v. City of New York, a landmark challenge to the New York Police Department’s stop-and-frisk policies. Scheindlin is expected to rule in favor of the plaintiffs—led by David Floyd, a medical student in the Bronx who was searched twice—who argue the N.Y.P.D. has infringed their constitutional rights with a program reliant on racial profiling and warrantless stops. “A lot of people are being frisked or searched on suspicion of having a gun and nobody has a gun,” Judge Scheindlin said at the hearing. “The suspicion turns out to be wrong in most of the cases.” Scheindlin’s decision, which she could issue as early as next month, may include a controversial remedy: the plaintiffs have requested the creation of an independent monitor for the N.Y.P.D., most likely in the form of a team of law-enforcement experts with authority to make sure that the department’s tactics respect constitutional protections.

New York City Mayor Michael Bloomberg, Police Commissioner Ray Kelly, and the new department chief, Philip Banks III, all oppose the idea, calling federal oversight a bureaucratic measure that would be, in Bloomberg’s words, “disastrous for public safety.” But there is little evidence that such monitoring undermines crime-fighting; quite the opposite.

Over the past fifteen years, the Department of Justice has accused police departments in two dozen jurisdictions, including New Orleans, Pittsburgh, Cincinnati, Detroit, Oakland, and Seattle, of offenses ranging from corruption and racial profiling to pervasive brutality. Each of those departments accepted a settlement agreement, also known as a consent decree, under which it was assigned, for a period of five to seven years, an independent monitor to institute new guidelines, review civilian complaints, and audit uses of force. If the department being monitored is uncoöperative, a federal judge can hold it in contempt. Only two of the seventeen jurisdictions that have served out their full consent decrees failed to meet their benchmarks within seven years. (One of those is the state of New Jersey, which decided to retain its independent monitor indefinitely.) “Any success these departments have had is owed to the role the independent monitor played,” Joshua Chanin, a professor of public administration and criminal justice at San Diego State University, said. “It’s much more likely that a department will not adhere to the spirit of reform without someone overseeing the process.”

One of the best-known examples of a monitor’s impact involves the man who once implemented New York’s stop-and-frisk policy, the former N.Y.P.D. commissioner William Bratton, and the Los Angeles force he went on to lead.

In the nineties, the L.A.P.D. was in a state of crisis. In 1991, a videotape captured three officers beating Rodney King, and in 1992, riots followed the officers’ acquittal. Seven years later, seventy L.A.P.D. officers, many of them members of the city’s hard-hitting anti-gang unit, were implicated in the Rampart scandal, which included allegations of stealing and selling seized drugs, planting false evidence, and, in one case, robbing a bank.

The L.A.P.D.’s relationship with many neighborhoods seemed irreconcilably shattered. Still, in 2000, when the Department of Justice threatened to sue the city unless it signed a consent decree that would allow the D.O.J. to appoint an independent monitor, Mayor Richard Riordan said the L.A.P.D. should be fixed internally. The police chief, Bernard C. Parks, was reportedly furious. The police union filed its own lawsuit against the city in a last ditch attempt to block it. The decree was approved anyway, and Kroll, the private security firm, was brought in to act as monitor. (William Finnegan wrote about Kroll for The New Yorker in 2009.)

One member of the Kroll team was the former New York City police commissioner William Bratton. After his two-year stint in New York had ended abruptly over personal differences with the then-Mayor, Rudolph Giuliani, he reluctantly drifted into the private-sector world of security consulting. In L.A., with the chief’s post open (Parks had departed), Bratton had a perfect opportunity to rebuild his legacy.

Bratton got the job—and the consent decree that came with it. Over the next seven years, his officers collected and made public detailed information about use of force, officer-related shootings, and racial profiling. It was an intense, and at times contentious, period. “No city wants to have federal oversight,” Bratton told me. “It’s an incredible encumbrance on the operations of the department.” Bratton said that the L.A.P.D. had to devote significant resources to new paperwork, but many of the reforms were successful. “Some elements of the decree were absolutely essential,” Bratton said. “The Department really did need to change its use-of-force policies and procedures, and it needed to change many of its accountability systems.” (Bratton, who is now running his own consulting firm, expressed some interest in returning to his old post in New York someday—“but at this stage of the game, that would be very, very speculative.”)

Shortly before he resigned, in 2009, Bratton commissioned a report from a team of criminal-justice professors at Harvard’s Kennedy School of Government. The researchers found that both community relations and public safety had improved. Violent crime in L.A. had dropped by almost fifty per cent; an unprecedented eighty-three per cent of residents approved of the job the L.A.P.D. was doing, and a majority believed the police treated all races and ethnicities fairly. Even more surprising, anonymous interviews revealed that morale on the force had improved. Officers expressed greater pride and were less afraid of being punished for honest mistakes, suggesting that transparency had led to a greater sense of fairness within the L.A.P.D.

In 2001, New York avoided a consent decree after the D.O.J. declined to sue the police department for the wrongful death of Amadou Diallo, the unarmed man shot forty-one times by officers in the Bronx. As a result, a handful of civil-liberties groups filed Daniels v. City of New York, the first class-action suit challenging the city’s stop-and-frisk policies. It emerged in Daniels that for every sixteen African-Americans stopped by the N.Y.P.D. only one was arrested. As Toobin recounts in his piece, Scheindlin presided in the Daniels case, too, but, before she reached any decision, the two sides agreed to a settlement. The N.Y.P.D. agreed to track every encounter based on “reasonable suspicion,” and to use public outreach to teach young people about their legal rights.

The plaintiffs in Floyd argue that the N.Y.P.D. has become diligent in its paperwork but far more liberal in its use of stop-and-frisks—the official tally has risen from ninety-seven thousand, in 2002, to six hundred and eighty-five thousand, in 2011. In a survey conducted by Baruch College last year, views of the N.Y.P.D. depended on race and ethnicity, educational attainment, and income. Only fifty per cent of blacks gave the N.Y.P.D. positive marks. Almost seventy per cent of New Yorkers reported believing the N.Y.P.D. to engage in racial profiling, but only groups likely to be profiled seem to care. About two-thirds of whites and Asians, and about sixty per cent of Hispanics, supported stop-and-frisk; more than half of black respondents opposed it. Two-thirds of white respondents believed police use good judgment in the stops; an equal share of black respondents said they did not.

These numbers are a reflection of why the city may lose in Floyd. But if it does, Los Angeles’s experience suggests that the police have less to fear than they may thinkif and when a monitor steps in. So would the people they protect. In the Harvard study, researchers asked members of the L.A.P.D. if patrol officers were treating people better while the force was being monitored. “Yeah, they have to,” one officer responded. “When I came on the job, some cops treated people like shit. Now they can’t.”

Photograph by Antonio Bolfo.