She is the hometown hero, the Oscar-winning actress and singer, Hollywood celebrity. But on Monday Hudson was the first witness in the murder trial of the man accused of killing her mother, brother and nephew.
In a nod to her celebrity, the court allowed her to come in through a back door to avoid the cameras in the courtroom lobby, but Hudson sat in the courtroom the entire day, along with her fiancé, David Otunga, and a bodyguard.
Hudson cried when asked about the last time she saw them alive.
The defendant, William Balfour had been married to Hudson's sister Julia, who is considered the star witness and followed Jennifer on the stand.
She told the court the family never really liked William Balfour, who was married to her sister Julia.
"None of us wanted her to marry William," she testified. "We did not like how he treated her."
After testifying, Hudson took a seat next to her fiancé in the courtroom as jurors looked on.
"It's going to have a tremendous impact," said Chicago-Kent law professor Richard Kling. "Sympathy and empathy."
Next up was the state's star witness and the reason prosecutors say Balfour killed the three family members. Julia Hudson listened as prosecutors played a recording of the 9-1-1 tape when she called after discovering her mother's body in their Englewood home.
"Oh my god, oh my god!" she is heard screaming. "Please help me. Someone killed my mother!"
Julia Hudson says when her marriage to Balfour started to go bad, he began threatening to kill her, threats she says he repeated a couple dozen times during their marriage.
"He said, 'if you leave me I will kill your family and I will kill you last.'" she said.
On cross examination however Balfour's attorneys asked why, if she felt threatened, she never reported the threats to police or sought an order of protection.
Nevertheless, legal experts say the alleged threats make for compelling evidence.
"It's going to be a difficult thing to overcome," Kling said. "Threats go to motive, whether or not he did it."
Defense attorneys also questioned why Julia Hudson continued to have a romantic physical relationship with Balfour in the weeks leading up the murders.
They appear to be trying to establish the possibility that neighborhood enemies of her brother Jason, an alleged drug dealer could be responsible for the killings.