A Study of Protests and Police Response

[R]esearchers at UC Berkeley [...] studied clashes between police and activists during the Occupy movement three years ago, found that protests tend to turn violent when officers use aggressive tactics, such as approaching demonstrators in riot gear or lining up in military-like formations.

Recent events in Ferguson, Mo., are a good example, the study's lead researcher said.

[...]

"Everything starts to turn bad when you see a police officer come out of an SUV and he's carrying an AR-15," said Nick Adams, a sociologist and fellow at UC Berkeley's Institute for Data Science who leads the Deciding Force Project. "It just upsets the crowd."

  SFGate

I can’t imagine why.

But finding the appropriate balance between being too aggressive and not aggressive enough hasn't been easy.

[...]

This week's protests in Oakland, to show solidarity with Ferguson activists, have been peaceful. Officers have restricted where marches can take place but have kept their distance.

Oakland police officials declined to be interviewed for this story.

[...]

In San Francisco, officials say they try to use force sparingly.

"We don't use tear gas. We don't use rubber bullets or dowels in crowd control," said police spokesman Officer Albie Esparza. "San Francisco is a professional protest city. We have protests here all the time. Our department is well versed in facilitating First Amendment rights."

[...]

During the Occupy protests [...] police in some cities deployed officers in small clusters rather than in skirmish lines. Such cities tended to see fewer clashes between demonstrators and police, the researchers said.

But, ask the Ferguson police chief – that’s no “show of force.”

Adams' team is still evaluating its findings and is incorporating other factors to determine whether they influence crowd behavior, including city rules for holding protests, an area's political makeup and local demographics. They expect to publish their findings by the end of the year.