The blurry photograph, taken by an unnamed witness, was mistakenly sent to reporters along with 61 pages of Zimmerman's college grades and other records.
The photocopied image appears to show the teenager lying face down on grass or a lawn, a United Press International review of the image indicates.
After the material was e-mailed, an aide to special prosecutor Angela Corey sent a second e-mail to news organizations stating a "photo depicting the killing of a person" was "confidential and exempt," based on state law, and was not intended to be released.
The Smoking Gun Web site posted the image under the headline, "Zimmerman Prosecutors in Huge Screw-Up." The Web site regularly posts legal documents, arrest records and police mug shots.
Zimmerman's academic records indicated he got D's in two criminal justice classes at Seminole State College in Sanford, Fla., but got a C in a course about violent predators, the New York Daily News reported Friday.
Zimmerman's C, in a class called "Evil Minds, Violent Predators," followed the lower grades in "Introduction to Criminal Justice" and a juvenile delinquency course, the transcripts indicated.
Zimmerman, on academic probation when he was expelled from the school following the shooting of Martin, got an A in criminal litigation and a B in criminal investigation, the transcripts show.
But Zimmerman's overall grade point average was lowered by poor math and science grades, including F's in two algebra classes.
Zimmerman's records surfaced Thursday shortly after his defense team announced it would seek a hearing under Florida's controversial "Stand Your Ground" self-defense law that could result in the dismissal of all criminal charges against the shooter.
Zimmerman, 28, has pleaded not guilty to a charge of second-degree murder and is free on $1 million bond. He has said the shooting of Martin on a rainy Feb. 26 night in Sanford was an act of self-defense, sparked by a fight that the teenager provoked. Martin, 17, was unarmed.
"The primary focus of a 'stand your ground' hearing is whether George Zimmerman reasonably believed that his use of his weapon was necessary to prevent great bodily harm to himself at the hands of Trayvon Martin," defense attorney Mark O'Mara wrote on his Web site.
The defense team said it would use the law -- which allows deadly force when someone fears severe injury or death -- because there is "clear support for a strong claim of self-defense," O'Mara wrote.
The hearing will likely occur in a few months, the Los Angeles Times reported.
Circuit Judge Kenneth Lester Jr., who has overseen much of the legal process so far, is expected to preside, the newspaper said.
Lester would decide the outcome, not a jury. The burden of proof lies with the defense, not the prosecution.
If the judge rules against the defendant, the case will still go to trial. If the charges are dismissed, Zimmerman will receive immunity from future prosecution in Martin's death.
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