SANFORD, Fla. -- Attorneys for the family of slain black teenager Trayvon Martin are asking the U.S. Justice Department to review reports that prosecutors undermined a police investigation of shooter George Zimmerman by overruling a detective who wanted to charge him.
The Justice Department's civil rights division had already agreed to review the local Florida investigation into the racially charged case that has riveted the country. Waves of demonstrations have called for Zimmerman's arrest.
A leading expert in forensic voice identification told the Orlando Sentinel late last week that Zimmerman was not the voice in the call to 911 moments before Martin was shot.
Tom Owen, forensic consultant for Owen Forensic Services LLC, used voice identification software to rule out Zimmerman, the Sentinel reported. Another expert contacted by the Sentinel, utilizing different techniques, came to the same conclusion.
Zimmerman claims self-defense in the shooting and told police he was the one screaming for help.
Lawyers for Martin's family are preparing a formal request that the federal government also investigate the specific report that state attorney's office prosecutors interfered with a homicide detective who wanted to charge Zimmerman with manslaughter.
"We are asking the Justice Department to investigate that," attorney Benjamin Crump, who has been retained by the Martin family as it pressures authorities to arrest Zimmerman, told Reuters late Saturday. "We are concerned about interference in the investigation."
Zimmerman, 28, who is half white and half Hispanic, was a neighborhood watch captain who shot dead the 17-year-old in a gated community on Feb. 26 after following him upon considering him suspicious.
Zimmerman has disappeared from public view but his father and brother have come to his defense in media interviews, saying Martin attacked Zimmerman and Zimmerman feared for his life when he shot the unarmed teen.
Police declined to arrest him, citing Florida's "Stand Your Ground" law, which permits citizens to use deadly force when they feel threatened with death or great bodily harm.
Sanford police detective Chris Serino, unconvinced by Zimmerman's story of self-defense, wanted to charge him with manslaughter but was overruled by the office of State Attorney Norm Wolfinger, the prosecutor whose district includes the city of Sanford, ABC News reported on Tuesday.
Wolfinger has declined all comment since removing himself from the case on March 22. Gov. Rick Scott named a special prosecutor, Angela Corey, to replace Wolfinger on the Trayvon Martin investigation. Corey has yet to say if she intends to charge Zimmerman, who remains free but in hiding.
A law enforcement source who has been informed by Sanford police investigators told Reuters that Serino was eager to make a case but encountered resistance from the prosecutor.
"Chris would have made a recommendation for manslaughter but Norm Wolfinger's office wanted it to be a slam dunk," the source said. "They don't want to hear that this is wrong or that is wrong with the case. That's the way this county does business."
A separate report by TheGrio.com, unconfirmed by Reuters, said Wolfinger left his home the Sunday night of the shooting to meet with Sanford police in person.
"Why did he get out of his bed and go to the police station that night and overrule the lead investigator?" Crump said. "It doesn't fit well."
Crump said Justice Department lawyers investigating the case invited him to provide relevant updates, and that his team would forward its request soon.
Federal authorities could step into the case if they believe the state investigation is lacking, and the Justice Department periodically takes an interest in matters where there is a potential civil rights violation.
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