From Boston to Los Angeles, police departments are bracing for large demonstrations when a grand jury decides whether to indict a white police officer who killed an unarmed black teenager in Ferguson, Missouri.

The St. Louis County grand jury, which has been meeting since Aug. 20, is expected to decide this month whether Officer Darren Wilson is charged with a crime for killing 18-year-old Michael Brown after ordering him and a friend to stop walking in the street on Aug. 9.

The shooting has led to tension with police and a string of unruly protests there and brought worldwide attention to the formerly obscure St. Louis suburb, where more than half the population is black but few police officers are.

For some cities, a decision in the racially charged case will, inevitably, reignite long-simmering debates over local police relations with minority communities.

"It's definitely on our radar," said Lt. Michael McCarthy, police spokesman in Boston, where police leaders met privately Wednesday to discuss preparations. "Common sense tells you the timeline is getting close. We're just trying to prepare in case something does step off, so we are ready to go with it."

In Los Angeles, rocked by riots in 1992 after the acquittal of police officers in the videotaped beating of Rodney King, police officials say they've been in touch with their counterparts in Missouri, where Gov. Jay Nixon and St. Louis-area law enforcement held a news conference this week on their own preparations.

"Naturally, we always pay attention," said Cmdr. Andrew Smith, a police spokesman. "We saw what happened when there were protests over there and how oftentimes protests spill from one part of the country to another."

In Las Vegas, police joined pastors and other community leaders this week to call for restraint at a rally tentatively planned northwest of the casino strip when a decision comes.

Activists in Ferguson met Saturday to map out their protest plans. Meeting organizers encouraged group members to provide their names upon arrest as Darren Wilson or Michael Brown to make it more difficult for police to process them.

In a neighboring town, Berkeley, officials this week passed out fliers urging residents to be prepared for unrest just as they would a major storm -- with plenty of food, water and medicine in case they're unable to leave home for several days.

In Boston, a group called Black Lives Matter, which has chapters in other major cities, is organizing a rally in front of the police district office in the Roxbury neighborhood the day after an indictment decision.

In Albuquerque, New Mexico, police are expecting demonstrations after having dealt with a string of angry protests following a March police shooting of a homeless camper and more than 40 police shootings since 2010.

Philadelphia police spokesman Lt. John Stanford said he anticipated his city will see demonstrations, regardless of what the grand jury returns.

But big-city police departments stressed they're well-equipped to handle crowds. Many saw large but mostly peaceful demonstrations following the 2013 not-guilty verdict in the slaying of Florida teen Trayvon Martin by neighborhood watch coordinator George Zimmerman. In New York, hundreds of protesters marched from Union Square north to Times Square, where a sit-in caused gridlock.

The New York Police Department, the largest in the nation, is "trained to move swiftly and handle events as they come up," spokesman Stephen Davis said.

In Boston, McCarthy said the city's 2,200 sworn police officers have dealt with the range of public actions, from sports fans spontaneously streaming into the streets following championship victories to protest movements like Occupy.

"The good thing is that our relationships here with the community are much better than they are around the world," he said. "People look to us as a model. Boston is not Ferguson."