Federal prosecutors sought to halt fact-finding Thursday in a civil case related to the ongoing bribery investigation involving ComEd that has implicated former House Speaker Michael Madigan, noting it goes “to the core” of a secret grand jury investigation. Meanwhile, a judge also Thursday tossed a separate lawsuit related to the ComEd investigation, finding that it fell short of proving allegations that bribery of Madigan directly led to passage of legislation favoring ComEd.