Large crowds of people assembling on the streets in reaction to the Zimmerman verdict have been reported across the United States, including in San Francisco, Washington, DC, New York and Chicago.
Demonstrators have been burning flags and smashing windows and police cars.
Los Angeles police issued a citywide tactical alert after about 200 protesters gathered in Leimert Park, LA Times cited police authorities as saying.
In Chicago, protesters marched with signs and shouted: “Who killed Treyvon Martin? The whole damn system?”
About 100 demonstrators gathered outside the Sanford, Florida courthouse since the jury began their deliberations on Friday, shouting slogans, waving placards and entering heated debate with one another about the case.
Night of incident
The deadly encounter took place on February 26, 2012, as Martin walked back to his father's fiancee's house through the rain from a Sanford convenience store. The 17-year-old was carrying Skittles and a drink.
Zimmerman, a neighborhood watch volunteer, spotted him and called police.
A 911 dispatcher told Zimmerman that officers were on the way and not to follow the allegedly suspicious person.
Nonetheless, Zimmerman got out of his car, later telling police he just wanted to get a definitive address to relay to authorities.
Sometime after that, Zimmerman and Martin got into a physical altercation. Some neighbors took notice: On one 911 call, anguished cries for help can be heard.
Who was yelling? Martin's mother testified she's "absolutely" sure it was her son; Zimmerman's parents said, with as much conviction, that it was their own child.
There are also disputes about who was the aggressor, and some also accuse Zimmerman -- who identifies himself as Hispanic -- of racially profiling the African-American teenager.
The prosecution argue that he wrongly and spitefully prejudged Martin as one of those "f***ing punks," as he's heard saying under his breath in his call to police, who had pulled off crimes in his neighborhood.
"The defendant didn't shoot Trayvon Martin because he had to," Assistant State Attorney John Guy said. "He shot him because he wanted to. That's the bottom line."
The defense contended that Martin jumped out of some bushes and pounced on Zimmerman as he was walking back toward his car that night, then punched him and slammed his head repeatedly into the concrete sidewalk.
NTJ/SHI