The lead investigator in the case wanted to charge Zimmerman with manslaughter in the weeks after the shooting but was overruled.
These are among the details revealed in nearly 200 pages of documents, photos and audio recordings released Thursday in a case that's riveted the nation. Yet it's still unclear what exactly happened and whether it was racially motivated.
The evidence supports Zimmerman's contention that he was being beat up when he fired the fatal shot. At the same time, it bolsters the argument of Martin's parents that Zimmerman was profiling Martin and that the whole confrontation could have been avoided if not for Zimmerman's actions.
Many of the pertinent questions remain unclear: What was in Zimmerman's mind when he began to follow Martin in the gated community where he lived? How did the confrontation between the two begin? Whose screams for help were captured on 911 calls? And why did Zimmerman feel that deadly force was warranted?
Another opportunity for answers isn't likely to come until a hearing later this year in which Zimmerman is expected to claim the shooting was justified under Florida's "stand your ground" law. Zimmerman's attorney, Mark O'Mara, didn't return a phone call seeking comment Thursday.
Martin's autopsy indicated that medical examiners found THC, the psychoactive ingredient in marijuana, when they tested Martin's blood and urine. The amount described in the autopsy report is such a low level that it would have played no role in Martin's behavior, said Larry Kobilinsky, a professor of forensic science at John Jay College of Criminal Justice in New York.
"This kind of level can be seen days after somebody smokes," Kobilinsky said. "If it comes up in the case, I would be surprised. It wouldn't benefit the defense, it wouldn't benefit the prosecution, and if the defense tried to bring it up, the judge would keep it out."
A police report shows the 17-year-old had been shot once in the chest and had been pronounced dead at the scene. The autopsy says the fatal shot was fired from no more than 18 inches away.
The evidence supporting Zimmerman's defense includes a photo showing the neighborhood watch volunteer with a bloody nose on the night of the fight. A paramedic report says Zimmerman had a 1-inch laceration on his head and forehead abrasion.
"Bleeding tenderness to his nose, and a small laceration to the back of his head. All injuries have minor bleeding," paramedic Michael Brandy wrote about Zimmerman's injuries in the report.
Whether Zimmerman was injured in the Feb. 26 altercation with Martin has been a key question. The 28-year-old has claimed self-defense and said he only fired because the unarmed teenager attacked him.
Zimmerman was not arrested for weeks because he invoked Florida's "stand your ground" law, which does not require a person to retreat in the face of a serious threat. He was released on bail and is in hiding while he awaits trial on a second-degree murder charge. He has pleaded not guilty.
Other evidence supports the contention of Martin's parents that Zimmerman was the aggressor.
The investigator who called for Zimmerman's arrest, Christopher Serino, told prosecutors that the fight could have been avoided if Zimmerman had remained in his vehicle and awaited the arrival of law enforcement. He said Zimmerman, after leaving his vehicle, could have identified himself to Martin as a concerned citizen and talked to him instead of confronting him. The report was written on March 13, nearly a month before Zimmerman's eventual arrest.
He said there is no evidence Martin was involved in any criminal activity as he walked from a convenience store to the home of his father's fiancee in the same gated community where Zimmerman lived.
The lawyer for Martin's parents seized on the investigator's recommendation.
"The police concluded that none of this would have happened if George Zimmerman hadn't gotten out of his car," said attorney Ben Crump. "If George Zimmerman hadn't gotten out of his car, they say it was completely avoidable. That is the headline."
The release of evidence did little to clear up whose voice is screaming for help in the background of several 911 calls made during the fight.