Alvarez said Hudson would not speak to the media about the verdict but would release a statement "at the appropriate time."
The jury foreman said he hoped the verdict would bring Hudson closure.
"I hope she can put this thing behind her and get on with the rest of her life," Robert Smith, a 47-year-old employee at Chicago Public Schools told reporters outside court.
Hudson, 30, rose to prominence as a 2004 "American Idol" finalist. But she became a bona fide star for her performance in the film adaptation of the musical, "Dreamgirls," for which she won the 2007 Academy Award for Best Supporting Actress.
Hudson was the first witness prosecutors called to testify, and during her more than 30 minutes on the stand she talked about her murdered family members and spoke endearingly about her nephew, Julian King, whom she called Tugga Bear. She said she knew Balfour since the eighth grade and always deeply disliked him.
Balfour had lived in the Hudsons' three-story Englewood home after marrying Julia Hudson in 2006. He moved out in early 2008 after falling out with his wife, but witnesses told jurors he often stalked the home.
The killings occurred the morning after Julia Hudson's birthday, and prosecutors said he became enraged when he stopped by the home and saw a gift of balloons in the house from her new boyfriend.
After his estranged wife left for her job as a bus driver on the morning of Oct. 24, 2008, prosecutors said Balfour went back inside the home with a .45-caliber handgun and shot Hudson's mother, Darnell Donerson, 57, in the back; he allegedly then shot Jason Hudson, 29, twice in the head as he lay in bed.
Prosecutors said Balfour then drove off in Jason Hudson's SUV with Julian — Julia's son, whom she called Juice Box — and shot the boy several times in the head as he lay behind a front seat. His body was found in the abandoned vehicle miles away after a three-day search.
The defense tried to counter the portrayal of Balfour as an embittered husband by noting Julia Hudson continued to have sex with him until just days before the killings.
In heated closings Wednesday, Thompson, almost shouting, said prosecutors had failed to prove their case. Prosecutor James McKay shot back that the defense was exploiting a popular misunderstanding that circumstantial evidence is lesser evidence.
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