Cook County Circuit Judge Jessica A. O’Brien has pleaded not guilty to federal mail and bank fraud charges filed against her earlier this month.O’Brien appeared for arraignment this morning before U.S. Magistrate Judge Sheila M. Finnegan at the Chicago federal courthouse. O’Brien’s plea was accepted and Finnegan explained O’Brien’s rights as they pertain to the charges against her.Federal prosecutors indicted O’Brien and one other person April 11 on one count of mail fraud …