It seems an awful lot of people in Ferguson, Mo., believe they already know what's coming their way a riot, or something close to it.

It's possible the violence that exploded this summer after a white cop shot and killed an unarmed black teenager is all behind them, but they doubt it.

There's been a pause in the action, that's all. And now the imminent release of a grand jury's findings could get everything in motion again.

Every Wednesday since the end of summer, a grand jury has met in St. Louis to hear evidence on whether to bring criminal charges against police officer Darren Wilson.

Wilson shot 18-year-old Michael Brown at least six times early one Saturday afternoon in August on a quiet street in Ferguson.

That much we know.

Brown and Wilson may have scuffled; there may have been a struggle for the officer's weapon. Brown may have been surrendering to police, hands in the air.

Maybe all that happened, or some of it, or none of it, that's what we don't know.

But while Ferguson waits for the grand jury's decision, it has dawned on those watching these events closely that the case is boiling down to the word of a handful of witnesses against that of one policeman.

And for many of them, past experience has shown that if that's the case there aren't likely to be charges.

Rules of engagement

Maybe they will be wrong, but they will not be unprepared.

A group calling itself the "Don't Shoot Coalition," for example, has presented police with a list of demands, including 19 "rules of engagement" for how to handle crowd reaction to the grand jury decision when it comes.

(Rule 7: police must not wear riot gear "except as a last resort." Rule 15: police must "tolerate minor law breaking," such as being bombarded with water bottles.)

Ferguson Police Chaplain

Member of the St. Louis County Police tactical team pray before heading out to deal with crowds and protesters in Ferguson, Mo. this summer. Months of unrest in Ferguson has led many police officers to seek counsel with chaplains, the force said. (The Associated Press)

The police have not agreed to these rules. Instead they have stockpiled extra pepper balls, smoke grenades, body armour and 2,000 pairs of plastic handcuffs.

Missouri Governor Jay Nixon has ordered the National Guard to stand by.

Constance Garnett, owner of the Taste of Honey Hair Salon in Ferguson, read the local mood and decided to get the big picture window on the front of her shop boarded up.

"If they should come and loot our area, then it's going to cost us," she said.

All over Ferguson, shopkeepers have covered the glass in their storefronts with plywood.

John Stephenson, the manager of a nearby gun shop says his sales of weapons for self-protection are up more than 50 per cent because of what happened in Ferguson in August.

"We're seeing new faces every day, dozens of new faces," he says, of his booming business.

The talk

African-American history is a history of injustice, a simple fact of life that black parents explain to their children just as parents explain things like the birds and the bees. They call it "the talk."

But the Michael Brown case has its particular history, too.

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Lesley McSpadden, mother of teenager Michael Brown, has asked people to stay calm after the grand jury report. (The Associated Press)

Witnesses said the teen was on his knees, arms up, facing officer Wilson when the cop shot him.

"Hands up! Don't shoot!" became a protest cry all over the U.S.

Four hours after the shooting, Brown's body still lay in his own blood in the middle of the street, while police shuffled around sorting out what to do next.

What they did not do next was arrest the officer who killed Brown. Wilson is on paid administrative leave.

Though paid leaves are not uncommon in the case of police shootings, that too became a source of national outrage.

Cornel West, the black activist and public intellectual arrived in Ferguson specifically to get himself arrested to make that point.

It worked. Police grabbed West and about 40 other protesters, said they were disturbing the peace and took them away in handcuffs.

Before they took him away, West said what he came to say: "Everybody knows if you shoot somebody down you should be arrested."

Jack in the Box

Actually, an on-duty police officer involved in a shooting is almost never arrested before a lengthy investigation.

"I can understand the concern about this," says Roger Goldman of the School of Law at Saint Louis University.

"But practice nationwide seems to be, in these officer-involved shootings in the line of duty, there tends not to be the arrest when there's so much up in the air."

Police Shooting Missouri Protests

Writer and activist Cornel West is taken into custody after performing an act of civil disobedience at the Ferguson, Mo., police station in October. "Everybody know if you shoot somebody down, you should be arrested." (The Associated Press)

In this case, there are also suspicions about the prosecutor who is guiding the grand jury.

Robert McCulloch has been the St. Louis County prosecutor since 1991, and has had his share of controversies.

The most famous is getting fresh play lately. It is a case from 2001 in which two undercover police officers shot and killed two unarmed black men as they sat in a car outside a Jack in the Box restaurant in Dellwood, the town next to Ferguson.

The men were drug dealers. The officers who killed them (21 shots fired) said they feared being run down by the men as they tried to escape in their car.

Only three of 13 witnesses told the grand jury back then that they saw the car move.

The police were not indicted.

Conflicting interests

McCulloch is thought to be sympathetic toward police. His father, brother, nephew and cousin all served with the St. Louis police. His father was shot and killed in the line of duty by a black man.

People see past history and conflicting interests.

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St. Louis County Prosecuting Attorney Robert McCulloch was asked to step aside in the Michael Brown case, but refused. He is overseeing the grand jury deliberations into whether the officer who shot Brown should be charged. (The Associated Press)

"I have no faith in him," said St. Louis Congressman William Lacy Clay. And that was before the Brown case even went to the grand jury.

Missouri State Senator Jamilah Nasheed asked McCulloch to step aside and appoint a special prosecutor in the Brown case. He refused.

"If you should decide not to indict this police officer, the rioting we witnessed [in August] will seem like a picnic," she said. "The black community will never accept that there was an impartial investigation from your office."

Only a fraction of police officers are ever indicted in excessive force cases. And even when they are, only a fraction of that fraction ends up convicted.

"These are extraordinarily difficult cases to win," says Goldman.

Society and the law treat on-duty officers differently from the rest of us.

They are expected to put their lives on the line to defend the public. In exchange, they are given authority to use physical force and weapons in their own defense.

Their snap judgments in the heat of the moment get the benefit of the doubt so long as the community trusts them.

But when police are not trusted in the community, and when the system that should hold them to account isn't either, it's reasonable to expect there will be trouble.

The protesters, the police, the governor of Missouri and even Michael Brown's family have all said that whatever the grand jury decides people should keep cool heads.

And maybe they will.

But in the meantime, the National Guard is suiting up and folks are boarding over their windows in Ferguson.