The prosecutor argued Zimmerman built a mountain of lies to conceal vengeful frustration and powerful determination not to allow someone he had already decided was a criminal to escape.
And, Guy contended, his under-his-breath commentary, captured on a police recording, about "f***ing punks" -- apparently directed at Martin -- revealed Zimmerman's hatred and ill-will toward the teenager.
That's important because under Florida law, a conviction on second-degree murder requires jurors to find that Zimmerman shot Martin out of "ill will, hatred, spite, or an evil intent."
"Common sense tells you it's the person talking like the defendant who had hate in his heart," Guy said.
"What is that when a grown man, frustrated, angry, with hate in his heart, gets out of his car with a loaded gun and follows a child? A stranger? In the dark? And shoots him through him heart? What is that?"
It was, defense attorney Mark O'Mara argued, nothing more than self-defense.
Defense: Case against Zimmerman full of 'what ifs'
"How many 'coulda beens' have you heard from the state in this case," O'Mara asked Friday. "How many 'what ifs' have you heard from the state in this case? They don't get to ask you that. No, no, no."
"Do not give anybody the benefit of the doubt except for George Zimmerman," the lawyer said.
O'Mara tried to discredit the prosecution's portrayal of Zimmerman as a frustrated, spiteful vengeance-seeker.
His client wasn't the aggressor, the defense argued, contending it was Martin who stalked Zimmerman and emerged from the darkness to pounce. There, O'Mara said, the teenager pinned Zimmerman to the ground and slammed his head into the sidewalk.
The defense attorney lugged a heavy block of cement to show jurors what, he said, Zimmerman had struck.
"And that is not an unarmed teenager with nothing but Skittles trying to get home," said O'Mara. "That was somebody who used the availability of dangerous items, from his fist to the concrete, to cause great bodily injury against George Zimmerman."
Guy ridiculed the argument that Zimmerman had suffered substantial injuries, saying repeated blows against concrete would have caused more damage than the rivulets of blood and bumps seen in photographs from the night of the shooting.
Authorities brace for post-verdict reaction
While this drama played out in a Sanford courtroom, authorities -- in that central Florida city and elsewhere around the state and the country -- braced for what might happen when or if the jury makes its decision.
In the weeks after Martin's death, tens of thousands attended rallies demanding Zimmerman's arrest and castigating authorities for their handling of the case. Some of them wore hoodies, as did Martin the night he was killed, in support of his family.
On Friday, a lawyer for the late teenager's family said that, while he wouldn't call Zimmerman a racist, "this case in its totality has a racial undertone to it."
Daryl Parks told CNN's Anderson Cooper that the defendant surmised Martin was a criminal like those who'd struck in his neighborhood before -- at least one of whom was black. "The problem, in this case, ... is that Trayvon was not one of those people," Parks said.
The defense, meanwhile, has strongly rejected accusations that Zimmerman is a racist, with O'Mara citing his client's work as a mentor to black children and his having taken a black girl to his prom as evidence of his non-racist beliefs.
But the perception is still out there, and it's a big reason Zimmerman moved out of his home after receiving death threats, his father Robert had said, then stayed at an undisclosed location awaiting trial.
His defenders have been passionate as well, especially about a person's right to defend himself with a gun when attacked. Debate swirled over Florida's "stand your ground" law, which allows those who believe they are in imminent danger to use deadly force to protect themselves.
Soon after the jury got the case, Zimmerman's family released a statement urging people to accept the verdict, whatever it is.
"Though we maintain George committed no crime whatsoever, we acknowledge that the people who called for George's arrest and subsequent trial have now witnessed both events come to pass," the family said. "We hope now that as Americans we will all respect the rule of law, which begins with respecting the verdict. The judicial system has run its course -- pray for justice, pray for peace, pray for our country."
Authorities similarly appealed for calm -- and took steps in case some did not heed those appeals.