Closing arguments begin in Zimmerman trial

(CNN) -- It all comes down to this: after more than a year of impassioned public debate, months of sometimes heated legal wrangling and more than three weeks of trial, the men trying to put George Zimmerman away and those seeking to keep him free faced off Thursday in closing arguments of his second-degree murder trial.

"A teenager is dead through no fault of his own, dead because a man made assumptions and acted on them, unfortunately, because his assumptions are wrong, Trayvon Benjamin Martin no longer walks on the earth," prosecutor Bernie de la Rionda said as he opened his argument.

"He profiled him as a criminal. He assumed certain things, that Trayvon Martin was up to no good. And that's what led to his death," de la Rionda said.

If things go as planned, the six-member jury could have the case as soon as Friday.

And when they do, they'll have more than one charge to consider in deciding the fate of the 29-year-old former neighborhood watch volunteer, who acknowledges shooting 17-year-old Trayvon Martin in 2012.

Judge Debra Nelson ruled Thursday that jurors will be allowed to consider manslaughter instead of the original second-degree murder charge against Zimmerman. But she denied prosecutors' request to let the jurors also consider third-degree murder in their deliberations.

Prosecutors argued that charge on the theory that Zimmerman had committed child abuse when he shot and killed 17-year-old Trayvon Martin on February 26, 2012. Nelson questioned a requirement in Florida law that would have required jurors to find Zimmerman intentionally committed child abuse.

"I just don't think the evidence supports that," she said.

Before Nelson's ruling, defense attorney Don West reacted angrily to the proposal, accusing prosecutors of springing the theory at the last minute and calling it a "trick."

"Oh my God," he told Nelson. "Just when I thought this case couldn't get any more bizarre, the state is seeking third-degree murder based on child abuse."

But Nelson agreed to allow the manslaughter charge after prosecutors argued that Florida law requires its inclusion.

In arguing unsuccessfully against the manslaughter charge, West told Nelson that Zimmerman believes that because the "state has charged him with second-degree murder, they should be required to prove it, if they can."

Prosecutors sought the additional charges to give jurors more options should they find Zimmerman didn't commit second-degree murder when he killed Martin.

Zimmerman, who did not testify, has said he shot Martin in self-defense. Prosecutors say he racially profiled the African-American teenager, following him through his Sanford, Florida, neighborhood despite a dispatchers' request not to, and then killed him without provocation.

Zimmerman is Hispanic.

In other issues, attorneys also argued over a defense request that Nelson tell jurors that following someone isn't a crime.

"You are absolutely allowed to follow, especially if you want to tell the police, that cannot be considered provocation, carrying a licensed firearm cannot be considered a threat," West argued.

But Nelson said there's no Florida law that explicitly says following someone is not illegal, so she couldn't tell the jury that it's part of the law.

She also denied the defense's request to instruct jurors about how they should view circumstantial evidence.

No testimony from Zimmerman

Zimmerman, who has spoken publicly about what happened that night, kept trial-watchers waiting until the very last minute Wednesday before announcing he wouldn't testify in his own defense.

After a series of testy exchanges with West, Nelson asked Zimmerman to say for himself what he wanted to do.

"After consulting with counsel," Zimmerman replied, he'd decided "not to testify, your honor."

Moments later -- and after Nelson refused a request from Zimmerman's team to dismiss the case before the jury could weigh in -- the defense rested its case.

Lawyer wrestles with foam dummy

The prosecution had once stated its intention to call up to three witnesses in the rebuttal phase of the trial but did not call any. One potential rebuttal witness was not called because the judge ruled prosecutors couldn't pursue one line of questioning. Another was ruled out because the prosecution wasn't certain the witness was available. The exclusion of the third potential witness wasn't explained.

That left Zimmerman's father, Robert Zimmerman, as the last witness in the widely watched trial.

He testified -- like his wife, Gladys, had earlier in the trial -- that he believes it was his son who was screaming on the infamous 911 recording of the altercation that ended in Martin's death.

Contrast their testimony to that of Martin's mother, Sybrina Fulton, who said she was "absolutely" certain that the panicked voice was that of her son. The late teenager's brother, Jahvaris Fulton, made a similar declaration in court.

The fatal gunshot

Absent a chance to hear directly from Zimmerman, the star Wednesday may have been a foam dummy.

Prosecutor John Guy and defense lawyer Mark O'Mara both grappled with the life-size model inside the courtroom, working to show rapt jurors the competing versions of what happened the rainy night Martin was killed.

Assistant State Attorney John Guy brought out the dummy in an effort to demonstrate that it would have been difficult for Zimmerman to retrieve his handgun from his pocket with Martin straddling him, as defense attorneys have argued was the case.

The fatal gunshot, Guy reminded defense witness Dennis Root, was fired at a 90-degree angle into Martin's body.

"Wouldn't that be consistent with Travyon Martin getting off of George Zimmerman and George Zimmerman raising the gun and firing it?" Guy asked Root, a use-of-force expert.

"It could be consistent with any kind of movement ... We weren't there so the info that we have is George Zimmerman's statement," he said.

Later, O'Mara straddled the dummy himself, pounding the back of its head against the carpeted courtroom floor, demonstrating how he says Martin gave Zimmerman the head wounds seen in police photographs from the night of the shooting.