A jury has begun deliberations in the murder trial of a Florida neighbourhood watchman who shot dead an unarmed black 17-year-old last year.
The judge told the six-women panel to consider whether George Zimmerman, 29, acted in self-defence and with justifiable use of deadly force.
Earlier, his lawyer said he had proven his client's "pure, unadulterated innocence" in Trayvon Martin's death.
But prosecutors said the accused had told a series of lies.
Mr Zimmerman could be acquitted, or convicted of second-degree murder or manslaughter.
Jurors have adjourned from their first day of deliberations on Friday after requesting a list of evidence from the judge. They will return for a second day of deliberations on Saturday.
After 12 days of testimony from dozens of witnesses, the jury must decide who was at fault in the fatal confrontation on the night of 26 February 2012 as Martin walked from a shop to the home of his father's fiancee in a gated community in Sanford, Florida.
While the nation awaits the outcome, police and city leaders in southern Florida say they are ready for any mass protests or even civil unrest if Mr Zimmerman walks free.
Following the jury's withdrawal on Friday, police asked residents of Sanford and the surrounding area to remain peaceful once a verdict is announced.
Defence lawyer Mark O'Mara told the sequestered jury in his closing arguments earlier on Friday that Mr Zimmerman's guilt had not been proven beyond reasonable doubt. He said the shooting was in self-defence.
The prosecution's case was built on a series of "could've beens" and "maybes", he added.
He said the defendant had shown no ill will, hate or spite during his encounter with Martin.
Mr O'Mara also challenged the jury to think about what Martin was doing for four minutes - after a friend on the phone told him to start running, but before he came face to face with Mr Zimmerman.
The defence lawyer fell silent for four minutes, and said the teenager had spent that amount of time planning his attack instead of returning home.
Mr O'Mara said the aggressor was Martin, "the guy who decided not to go home when he had a chance to".
Summing up, he used a slideshow, an animation of the fight, and cardboard cut-outs of Mr Zimmerman and Martin.
'Every child's nightmare'
In rebuttal, prosecutor John Guy argued that Mr Zimmerman had repeatedly lied in his statements about the shooting.
Mr Zimmerman's account of how he grabbed his gun from his holster at his waist as the teenager straddled him is physically impossible, the prosecutor said.
"The defendant didn't shoot Trayvon Martin because he had to - he shot him because he wanted to," Mr Guy said. "That's the bottom line."
"Isn't that every child's worst nightmare, to be followed on the way home in the dark by a stranger?" he added. "Isn't that every child's worst fear?"
Without explicitly discussing race, the prosecution has suggested Mr Zimmerman assumed the African-American teenager, who was wearing a hooded sweatshirt as he walked in the rain, was up to no good.
But the defence says Martin punched their client, slammed his head into the pavement and reached for Mr Zimmerman's gun.
The accused, who was legally armed with a pistol, had been sitting in his vehicle on a dark street when he saw Martin.
Mr Zimmerman telephoned police to report a suspicious person, then left his vehicle in apparent pursuit of the teenager.
Shortly afterwards, Martin was dead of a gunshot wound to the chest.
The defendant, who identifies himself as Hispanic, could face life in prison if convicted on the murder charge. If found guilty of manslaughter, he could face up to 30 years in prison.
Last year, the case prompted mass, peaceful protests across the US, with critics questioning why it took police six weeks to arrest Mr Zimmerman.