One witness, a 13-year-old boy, told investigators he saw a man in a red shirt crying for help, but told reporters he could not tell what clothes the injured person wore. Zimmerman wore a reddish-orange jacket.

Another witness, No. 12, said she wasn’t sure who was on top of whom. But when she had time to think about it, she decided it was definitely Zimmerman on top, because she had seen him on TV and he was larger.

Prosecutor Bernardo de la Rionda asked her if by larger, she meant “broader.” “Yes,” she said.

Zimmerman was much shorter than Trayvon, but wore a size 38 pants and was consistently described by most of the witnesses as the larger of the two.

Newirth, of the Innocence Project, said memories are affected by stress, the presence of a weapon, and can be influenced by everything from the question an investigator asks, to media reports and statements of other witnesses. The phenomenon is known as “memory contamination.”

“I think in a case like this, there is likely contamination coming from all over the place,” she said. The Innocence Project is not involved in this case and has not reviewed the evidence.

Studies show people who witnessed the same simulated event reported different memories depending on the language used by the questioner. People who were given false information about the simulated event often incorporated the made-up details into their own accounts.

Newirth said studies also show people’s memories change as they learn more information about the incident they saw, making it critical to get their full accounts early and in their own words.

The recordings submitted as evidence by the Sanford Police conducted the night of Trayvon’s killing showed investigators only taped about two minutes with each person.

“Memories do not improve over time,” she said. “In fact, they worsen over time and the worsening, which is demonstrated by something called the memory curve, begins very soon after the memory is created.”

“Ear witnesses,” who heard something but did not see it, she said, are even less reliable then eyewitnesses.

There were no follow up interviews for the teen witness or the two ear-witnesses who vehemently believed Trayvon Martin called for help and that Zimmerman shot Trayvon from some distance from where the fight occurred. FDLE tests on Trayvon’s shirt show he was shot at very close range.

In an interview with The Miami Herald, Zimmerman’s defense attorney, Mark O’Mara, said the witness testimony seemed to change, and sometimes appeared to be swayed by the prosecutor’s probing. At least one witness said she was basing her testimony on a 2005 picture of Zimmerman, when he weighed significantly more than he did at the time of the shooting.

“It’s a good thing they have to prove this case,” he said of the state attorney. He declined to comment further on the witness statements, saying he is prohibited by attorney rules of conduct.

“If I were to say, ‘Hey, the evidence looks great for my guy,’ it would be commenting on the evidence,” he said. “I’m the one who has been complaining that everyone has been making up their mind with less than half the evidence. I am trying to undo the horrible prejudice done to my client.”