Police and protesters have been clashing in Ferguson, Mo., since the shooting death of teen Michael Brown on August 9.
Toronto's police force faced angry protesters when the city hosted the G20 political summit, and some of the lessons they learned could be applied in Ferguson.
When anti-G20 protesters started rioting in Toronto, police used tear gas in the city for the first time.
An after-action report later revealed that "displays of real or implied force can lead to negative crowd reactions that may escalate a situation."
Steven Summerville, a former police trainer, agrees.
"You don't wish to create alarm. You don't wish to create anger or fear with your crowd," he said. Police need to "get out there" and lighten up on the uniform, he said.