Key mistakes sway jury in Zimmerman trial

The prosecution asked the judge to instruct the jury that it could consider who was the first aggressor in the altercation between Zimmerman and Martin. If the judge had agreed to give that instruction, the jury might have concluded that, by following Martin, Zimmerman provoked a physical response from Martin. The defense objected to the instruction, and the judge decided not to give the first aggressor instruction.

The jury was instructed to consider only whether Zimmerman reasonably believed deadly force was necessary to prevent imminent death or great bodily harm to himself - when he later tussled with Martin on the ground. The jury was also told Zimmerman had no duty to retreat, that he could stand his ground, and meet force with force- including deadly force - if he was not engaged in an unlawful activity and was attacked in a place he had a right to be. Finally, the judge instructed the jury that if it had a reasonable doubt about whether Zimmerman was justified in using deadly force, they should find him not guilty.

The instructions prevented the jury from considering whether Zimmerman was the first aggressor when he got out of his truck and began following Martin. When Zimmerman told the 911 operator, "Shit, he's running," the operator asked, "Are you following him?" Zimmerman said that he was. "OK, we don't need you to do that," the operator told Zimmerman. But Zimmerman followed Martin nevertheless. Rachel Jeantel testified that Martin told her on the cellphone he was being followed by a "creepy ass cracker."

The jury was only given partial instructions on self-defense – those parts that helped Zimmerman. They were prevented from considering whether Zimmerman might have been the first aggressor, which would have negated his claim of self-defense.

Ultimately, nothing mattered to the jury, Juror B-37 told Cooper, except whether Zimmerman feared for his life in the seconds before he shot Martin.

Juror B-37 said that Zimmerman was guilty of nothing more than "not using good judgment." She added, "Both were responsible for the situation they had gotten themselves into."

Sanford police officer Chris Serino, the chief investigator on the case, testified that, given all the evidence, he believed Zimmerman was telling the truth. It is well-established that witnesses cannot make credibility judgments – it invades the jury's exclusive province of determining the credibility and weight of any evidence. But the prosecution didn't object to Serino's testimony until the next morning, at which point the judge told the jury to disregard it. Yet the damage was done, and Serino again testified that there were no significant inconsistencies in Zimmerman's statements to police.

From the beginning, Serino did not believe there was enough evidence to file criminal charges against Zimmerman. The officer told the FBI that he was pressured into making the arrest. Zimmerman finally was charged for Martin's death only after a powerful national outcry, and the governor's appointment of a special prosecutor - 40 days following the killing.

Serino testified, "In this case, [Zimmerman] could have been considered the victim also." Likewise, Juror B-37 felt sorry for both of them - the dead boy and the shooter alike.