Little is known about the nature of the complaint, the Orlando Sentinel reported Tuesday, including what it alleges or who made it. But its origin is O'Mara's work on the high-profile Martin case.
O'Mara volunteered to represent Zimmerman during the trial and successfully fended off a second-degree murder charge prosecutors filed against the former Sanford neighborhood watch captain who shot and killed Martin, an unarmed black teenager, during a confrontation in the gated community.
Since then, the relationship between O'Mara and Zimmerman has soured. Following the trial, O'Mara, a respected $400-per-hour criminal defense and divorce attorney from Orlando, handed Zimmerman a $2.5 million bill for his services, saying he logged more than 3,000 hours on the case.
In subsequent legal cases against Zimmerman, O'Mara has said he will no longer represent him.
O'Mara declined to comment on the bar association's ethics investigation.
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