CHICAGO -- Chicago prosecutors created a buzz by calling Oscar-winner Jennifer Hudson as their first witness during the trial of the man accused of killing her mother, brother and nephew. But the hard part starts Tuesday, when they'll have to get down to the nitty-gritty of their case.With no surviving witnesses to the murders, prosecutors must offer overwhelming circumstantial evidence that William Balfour, the ex-husband of Hudson's sister, committed the grisly crime on Oct.