Neighborhood watch volunteer George Zimmerman was cleared of all charges Saturday in the shooting of Trayvon Martin, the unarmed black teenager whose killing unleashed furious debate across the U.S. over racial profiling, self-defense and equal justice.

Zimmerman, 29, blinked and barely smiled when the verdict was announced. He could have been convicted of second-degree murder or manslaughter. But the jury of six women, all but one of them white, reached a verdict of not guilty after deliberating well into the night Saturday.

Martin's mother and father were not in the courtroom when the verdict was read; supporters of his family who had gathered outside yelled "No! No!" upon learning of the not guilty verdict.

The jurors considered nearly three weeks of often wildly conflicting testimony over who was the aggressor on the rainy night the 17-year-old was shot while walking through the gated townhouse community where he was staying.

Defense attorneys said the case was classic self-defense, claiming Martin knocked Zimmerman down and was slamming the older man's head against the concrete sidewalk when Zimmerman fired his gun.

"We're ecstatic with the results," defense attorney Mark O'Mara after the verdict. "George Zimmerman was never guilty of anything except protecting himself in self-defense."

Another member of his defense team, Don West, said: "I'm glad this jury kept this tragedy from becoming a travesty."

Prosecutors called Zimmerman a liar and portrayed him was a "wannabe cop" vigilante who had grown frustrated by break-ins in his neighborhood committed primarily by young black men. Zimmerman assumed Martin was up to no good and took the law into his own hands, prosecutors said.

State Attorney Angela Corey said after the verdict that she believed second-degree murder was the appropriate charge because Zimmerman's mindset "fit the bill of second-degree murder."

"We charged what we believed we could prove," Corey said.

As the verdict drew near, police and city leaders in the Orlando suburb of Sanford and other parts of Florida said they were taking precautions against the possibility of mass protests or unrest in the event of an acquittal.