WASHINGTON (AP) — A George Washington University law professor is filing a complaint against Baltimore State’s Attorney Marilyn Mosby over the investigation and prosecution of six police officers in the death of a black man who was critically injured in the back of a police van.

John F. Banzhaf III says his complaint is being filed Wednesday with Maryland’s Attorney Grievance Commission. Among other things, Banzhaf says in his 10-page complaint that Mosby appears to have violated Maryland’s rules of professional conduct for lawyers, which requires that a prosecutor refrain from prosecuting a charge unless it is supported by probable cause.

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So far, Mosby’s office has tried three of the six officers charged in Freddie Gray’s 2015 death. Two prosecutions ended in not guilty verdicts and a third resulted in a mistrial.

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Gray’s death set off protests and rioting in the city.

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