Good Morning America

By MATT GUTMAN

Enhanced video footage of George Zimmerman being taken into custody less than 30 minutes after he shot and killed Florida teenTrayvon Martin shows the neighborhood watch captain with an injury to the back of his head.

The never-before-seen evidence of an injury to Zimmerman, in this case a gash or mark to his head, would appear to back his claim that he shot Martin in self defense after he was attacked by Martin on the night of Feb. 26 in Sanford, Fla

Zimmerman, 28, claims Martin, 17, punched him in the nose, knocked him down and repeatedly slammed his head into the ground.

The police surveillance video, first obtained exclusively by ABC News last month and clarified by Forensic Protection, Inc., shows Zimmerman exiting the police cruiser with his hands cuffed behind his back. Zimmerman is frisked and then led down a series of hallways, still cuffed. At one point, one of the officers stops to look briefly at the back of Zimmerman's head.

There was no obvious sign of any injury to Zimmerman's head or face on the video until it was enhanced. But the enhanced video does not show any visible injury to Zimmerman's nose, nor any signs of blood on his shirt.

Police Video Surveillance of George Zimmerman

The initial police report noted that Zimmerman was bleeding from the back of the head and nose, and his lawyer later claimed that Zimmeran suffered a broken nose. After receiving medical attention at the scene of the shooting, it was decided that he was in good enough condition to travel in a police cruiser to the Sanford, Fla., police station for questioning. He did not check into the emergency room following the police questioning.

The surveillance tape of Zimmerman, later released by the Sanford Police Department, could be used as evidence if Zimmerman is brought up on charges, sources tell ABC News.

Zimmerman's lawyer, Craig Sonner, has said his client felt "one of them was going to die that night," when he pulled the trigger.

The case has gained national prominence with rallies across the country demanding that Zimmerman be arrested and charged with murder.

Lawyers for Martin's family sent a letter to the Justice Department today asking that the federal probe into the killing look into the fact that Sanford Police Chief Bill Lee met with State Attorney Norm Wolfinger on the night of shooting. Lawyer Benjamin Crump also claims in the letter that members of Zimmerman's family were also present in the police station that night.

The lead homicide investigator, Chris Serino, wrote in an affidavit that he recommended manslaughter charges be brougth against Zimmerman but was advised by the prosecutor not to file charges because there was not enough evidence for a conviction, sources have told ABC News.

"We look forward to your thorough and comprehensive review of the suspicious circumstances surrounding this meeting," Crump wrote.

State prosecutors are expected to go before a Seminole County grand jury on April 10 to determine what, if any, files should be charged.

An analysis of a 911 call done over the weekend by the Orlando Sentinel determined that screams for help overhead on a 911 came from Martin, although Zimmerman's family insist they recognize his voice in the screams.

Two evidence experts consulted by the Sentinel found the voice heard in a 911 call placed by a woman in a home near where the shooting occurred was only a 48 percent match to Zimmerman's voice. One of the experts, Tom Owen, told the Sentinel to reach a positive match he would expect higher than 90 percent.

"As a result of that, you can say with reasonable scientific certainty that it's not Zimmerman," Owen told the paper.

Owen,the chair emeritus at the American Board of Record Evidence, was not able to determine if the voice was that of Martin, the Sentinel reports, because he did not have audio of the teen's voice to compare to the shouts for help in the 911 call.

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