CHICAGO (AP) – A judge has appointed a former federal prosecutor to investigate the Cook County state’s attorney’s office for wrongdoing during the aborted re-trial of an accused cop killer. Judge Alfredo Maldonado on Wednesday appointed Lawrence Oliver to investigate the Cook County state’s attorney’s office and a former employee who allegedly lied on the witness stand during the third trial of Jackie Wilson. Former Assistant State’s Attorney Nicholas Trutenko in October testified he had a personal relationship with a jail informant who helped convict Wilson at a second trial in 1989. The charges against Wilson were dropped as a result of Trutenko’s testimony. Oliver can convene a special grand jury to investigate and potentially bring criminal charges against Trutenko.