William Balfour was the estranged husband of Hudson's sister, Julia. He is charged with three counts of first degree murder in the Oct. 2008 killings.
Her mother and brother were found dead in the family's Chicago home in the South Side. Her 7-year-old nephew was found in a car 10 miles from the home a few days later.
Prosecutors allege the motive for the killings was jealousy over Hudson's sister dating another man.
Court filings include Hudson's interviews with detectives following the murders. According to the documents, Hudson said she had known Balfour since childhood and had advised her sister against marrying him.
Hudson rarely discusses the murders publicly. It is unclear if she will actually testify at the trial, which is slated to being April 9.
The Associated Press contributed to this report.
Correction: In an earlier version of this story, one instance of "Hudson" was incorrectly labeled "Houston."