Fulton County District Attorney Fani Willis has been subpoenaed to testify in a fellow prosecutor’s divorce proceedings, according to a court filing, in a move that could reveal more information about claims that Willis and the colleague engaged in an improper affair as they prosecute former President Donald Trump.

Mike Roman, one of Trump’s 14 remaining co-defendants in the sweeping racketeering indictment, filed a complaint Monday that Willis has engaged in personal relations with the special prosecutor she hired to lead the case, who has received hundreds of thousands of dollars for his work.

A process server said he arrived at Willis’s office in Atlanta on Monday with a subpoena seeking testimony in the Cobb County divorce case of Nathan Wade, a local attorney she hired to be special prosecutor in the Trump case, and his wife, Jocelyn Wade, according to court filings reviewed by the Wall Street Journal.