Federal appeals judges this week fired skeptical questions at lawyers for key players of the largest mortgage fraud ring ever prosecuted in Georgia.

During a lively, 90-minute session on Tuesday at the 11th U.S. Circuit Court of Appeals, attorneys for the convicted ringleader, real estate investor Phillip E. Hill, and his co-defendants asked for their 2007 guilty verdicts to be tossed out. Among their claims: prosecutors discriminated against African Americans during selection and violated a defendant’s agreement to provide information in return for immunity.