O'Mara was co-counsel for Zimmerman when the former Neighborhood Watch volunteer sued the network broadcaster just over a year ago, accusing it of falsely portraying him as racist in five reports.
At the time, Zimmerman had admitted killing Trayvon Martin, an unarmed black 17-year-old, but had not been arrested, and the investigation was a national story.
A few weeks later Zimmerman was charged with second-degree murder, but a Seminole County jury acquitted him last year.
His defamation suit has sat dormant for 11 months. Both sides agreed last February that they'd do nothing until Zimmerman's criminal case was closed.
Although his criminal trial is over, the case is still technically open. That's because O'Mara and co-counsel Don West asked Circuit Judge Debra Nelson to impose sanctions against prosecutor Bernie de la Rionda, accusing him of hiding evidence and creating delays.
Nelson presides over Zimmerman's defamation case as well. She called Thursday's hearing, saying she'd received a letter from Zimmerman's main defamation lawyer, James Beasley Jr. of Philadelphia, saying there were no pending matters in the criminal case, so it was time to move forward.
O'Mara did not appear in court , but a lawyer from his firm, Lorna Truett, took part by phone. The judge asked if her firm was withdrawing its motion for sanctions, and she said she was unsure. Based on that, the judge ruled the libel case cannot move forward.
The judge removed O'Mara, at his request, as one of Zimmerman's defamation lawyers.
O'Mara's would not say why he was leaving the case but in a prepared statement, called Zimmerman's claim "strong."
One of the law firms defending NBC is Thomas & LoCicero, which also represents the Orlando Sentinel.
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