Cincinnati lawyer Stan Chesley, who helped negotiate Kentucky’s $200 million fen-phen settlement, has disclosed he won’t testify for three fellow lawyers accused of bilking their clients out of $46 million.

Chesley, a nationally known class-action lawyer, had previously defended the conduct of attorneys Shirley Cunningham Jr., William Gallion and Melbourne Mills, supporting their contention that they had to withhold millions of dollars from the fen-phen clients in the event that additional claims arose.

By refusing to testify for the attorneys, now accused of conspiracy to commit wire fraud, “Chesley obviously wants to distance himself” from them, said attorney Angela Ford, who now represents the former fen-phen clients, who’ve already won a $42 million civil judgment against Cunningham, Gallion and Mills.

The three lawyers are scheduled to be tried May 12 in U.S. District Court in Covington, and Cunningham and Gallion had listed Chesley as an expert witness.

Chesley’s refusal to serve in that role—disclosed in court papers filed late last month—will make it more difficult for the lawyers to argue they relied on his advice in the fen-phen litigation, Ford and other lawyers said.

While they could subpoena him to appear in court, he could refuse to testify, citing his Fifth Amendment right against self-incrimination.

Chesley’s criminal lawyer, Scott C. Cox of Louisville, said Chesley will “honor any subpoena,” but he wouldn’t say if his client would testify.

Chesley is not charged in the criminal indictment, though he is named as a defendant in the ex-clients’ lawsuit, which alleges that he received a $20.5 million fee—about $7 million more than he should have been paid.

Cox and government lawyers declined to say whether Chesley will testify for the prosecution or has struck an agreement with the government not to appear for the defense.

Cox said only that Chesley elected not to appear as a witness for his former colleagues because his role was limited to “negotiating the best possible settlement for the three lawyers currently charged.”

“Because his involvement was so limited,” Cox said, “I don’t anticipate him being a witness for either side in the case.”

The fen-phen plaintiffs say Chesley played a major role in the underlying case, and they point to an affidavit from attorney David Helmers, who worked for Gallion and said Chesley “actively assisted” in the fen-phen case.

Chesley’s withdrawal as a witness is one of several developments in the criminal prosecution of what Ford alleges is the largest theft in Kentucky history.