FERGUSON, Mo. » During a recent demonstration here against a grand jury’s decision not to indict a white police officer in the killing of an unarmed black teenager, a 28-year-old black protester approached a white police sergeant in a line of heavily armed, mostly white officers. The protester did not taunt, and the sergeant did not issue orders. They simply talked past each other.

"I ain’t never seen a police officer do anything good," the man said. "If I had to worry about someone chasing me with a knife and I saw you, I would be more worried about you killing me than that person with a knife."

"How do I change your perception?" the officer, Sgt. Kevin Stevener, asked.

"I keep telling you the whole time – stop killing us," the man replied.

As the St. Louis region tries to recover from the death of the teenager, Michael Brown, which laid bare racial tensions and set off months of sometimes violent protests, one of the biggest unresolved problems in Ferguson is the deep suspicion, anger and mistrust that separates its mostly black population from its almost entirely white police force.

It is a problem that police departments across the country are now confronting in the midst of an anguished national debate over whether the police too often use deadly force against minorities. New York, where a grand jury on Wednesday declined to indict a white officer in the July death of an unarmed black man, and Cleveland, where the Justice Department will require an independent monitor of the police department in the wake of fatal police shootings, are just the most recent examples.

Closing this gap, experts say, will require a broad shift in police training and culture, and in officers’ behavior and attitudes – the sorts of almost philosophical changes that are complex, time-consuming and, at times, costly. Creating civilian review boards and putting body cameras on officers, as New York started doing on Friday, are the first steps in a process to improve community relations that could take years.

Attorney General Eric H. Holder Jr., in announcing the findings of the Justice Department’s scathing review of the Cleveland Police Department on Thursday, said the department’s actions stemmed from "systemic deficiencies" that included inadequate training and engagement with the community. This is not unlike what critics have said about the Ferguson Police Department.

"You’ve got to bring officers out there and make them stand up in somebody’s living room, make them stand up in front of a church," said Russ Leach, a former police chief in Riverside, California, who oversaw court-ordered changes there after the fatal shooting in 1998 of a 19-year-old black woman by four white officers.

"Giving the cops bulletproof vests and cameras, that’s fine," Leach said. "But what needs to be managed is the mentality. You can’t have a siege mentality and be an effective police officer."

Last Monday at the White House, in response to the events in Ferguson, President Barack Obama announced the formation of a task force to examine ways to strengthen community policing, a law enforcement strategy that focuses on preventing crime and addressing neighborhood concerns rather than merely reacting to crime.

After a steady increase during the late 1990s, community policing programs declined as the federal government shifted more grant money to fighting terrorism. From 2000 to 2007, the number of full-time community policing officers nationwide fell by more than half, to 47,000 from 103,000, according to Justice Department data.

"I think that community policing has been there all along, but it has gotten less attention," said Laurie O. Robinson, a former Justice Department official who is leading Obama’s task force with the Philadelphia police commissioner, Charles H. Ramsey.

"It didn’t have the emphasis from Washington, from the White House," Robinson said. "It’s about local police departments having the capacity, ability and willingness to build relationships, to establish a positive dialogue, to hire a diverse workforce. And building that legitimacy and that trust is not something that happens overnight, obviously."

Several police departments that have made changes after fatal shootings or excessive-force scandals, including those in Cincinnati, Los Angeles and New Orleans, provide models for Ferguson. Such changes have often been a result of public and political pressure; court orders; state intervention; and agreements, known as consent decrees, between the Justice Department and the police agencies.

In Cincinnati, the Rev. Damon Lynch III helped lead a push to overhaul the police department after the fatal shooting in 2001 of an unarmed 19-year-old black man, Timothy Thomas, by a white officer. The filing of a class-action lawsuit against the city led to a 2002 agreement among community leaders, the police and others.

"The cops had to sit through a process that initially they hated, but at the end of the day, most people in Cincinnati, cops included, will tell you we’re better for it," said Lynch, who has twice visited Ferguson to hand out copies of the agreement.

Even before the Ferguson police officer, Darren Wilson, shot and killed Brown on Aug. 9 in a brief encounter near the predominantly black Canfield Green apartments, tensions were high. One black Canfield Green resident, Kevin Seltzer, 30, said some residents would car pool to the convenience store just a few blocks away because they did not want to risk being harassed by officers if they walked.

The mistrust was apparently mutual, as Wilson made clear in his testimony to the grand jury investigating the killing.

Wilson, who did not get out of his vehicle when, just before the shooting, he asked Brown and his friend to walk on the sidewalk, described Canfield Green to prosecutors as "an anti-police area for sure," adding: "There’s a lot of gun activity, drug activity. It is just not a very well-liked community. That community doesn’t like the police."

Seltzer, standing at Brown’s flower-strewn memorial at Canfield Green recently, rejected Wilson’s description. "We weren’t anti-police," Seltzer said. "We were afraid of the police. We tried to avoid the police."

Some community-policing experts said Ferguson needed a change in police leadership, including the departure of Chief Thomas Jackson, who has declined to resign. Others suggested there would be little progress until the Justice Department completed its broad civil rights investigation of the Ferguson police’s practices, similar to the review it just finished in Cleveland.

In the meantime, relations between the two sides seem to have only gotten worse. At Canfield Green, some residents have tried to police themselves, conducting their own security patrols, handing out body cameras to monitor the police and complaining that police officials have made few, if any, efforts to improve their communication with residents.

Some experts say the onus for change should be on the police.

"They cannot continue to engage in a mind-set that they’ve done no wrong, that everything they’ve done has been by the book and it’s OK to continue down that path," said Joseph Brann, the former director of the Justice Department’s community-oriented policing office and a former police chief in Hayward, California. "If they do that, there’s no hope for reform."

In Ferguson, late in the night of rioting that followed the grand jury’s decision, an African-American man walked alone holding a sign that read, "Darren Wilson Is a Murderer."

The man, Andre’ C. Coffer, 49, is a certified public accountant whose office is across the street from Ferguson City Hall. He said he was fed up with being pulled over by the police in Ferguson and other municipalities – traffic stops that he said were a result of racial profiling and that, because he missed a court date, led to the suspension of his driver’s license.

"It’s been a simmering anger," Coffer said. "This is bigger than Mike Brown. There’s not too many CPAs picketing tonight. But I’ve got a vested interest in this. I’ve got four sons."

Manny Fernandez, New York Times

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