George Zimmerman, son of a white father and a Hispanic mother, has said he acted in self defence when he killed Trayvon Martin, 17, on a rainy night in February 2012.
The killing riveted the United States at the time, drawing an expression of sympathy from President Barack Obama. It also sparked a debate on so-called "stand your ground" laws in Florida and other gun-friendly states.
Sanford police initially released Zimmerman after the shooting because they said he was acting in line with "stand your ground" rules, which give immunity to those who use firearms when they feel their lives are in jeopardy.
But a public outcry and dozens of protests about the killing ensued, accompanied by allegations from Zimmerman about Martin's conduct amid distress and frustration from Martin's relatives about how police had handled the case.
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Public opinion has divided roughly into those who think the shooting of an unarmed black youth was racially motivated and those who see it as yet another instance of gun violence in a nation obsessed with firearms.
"We are tired of going to jail for nothing and others going home for something," black activist Al Sharpton said at a rally in March 2012.
"Zimmerman should have been arrested that night ... You cannot defend yourself against a pack of Skittles and iced tea." He was referring to what Martin was carrying with him the night of the shooting.
The "stand your ground" law is one of the most lax gun-use laws in the United States and was the target of much criticism after Martin's killing.
African-American activists such as Sharpton and Jesse Jackson have said recently they believe the black community will respect whatever verdict comes out of the trial, which could last more than a month.