CHICAGO (CBS) — Prosecutors say the man accused of killing the family of actress Jennifer Hudson told Hudson’s sister Julia: “I’m going to kill your family first, then kill you.”

As WBBM Newsradio’s Steve Miller reports, prosecutors say William Balfour made the threat at least 25 times.

LISTEN: WBBM Newsradio’s Steve Miller reports

“If you leave me, I’ll kill you,” prosecutors say he told Julia Hudson on July 31, 2008. “You’ll be the last to die.”

A month or so before the murders, prosecutors say Balfour threatened to kill Julia Hudson’s new boyfriend.

He made that threat again when Julia told him she was planning to be intimate with her new boyfriend on her birthday, Oct. 23, prosecutors said.

And then on Oct. 24, 2008, after the murders but before the body of Hudson’s 7-year-old son, Julian King, was found inside a sport-utility vehicle, prosecutors say Balfour called Julia Hudson and Hudson asked him where he was. He stuttered and said “up north,” prosecutors said.

Balfour is charged in the shooting deaths of Jennifer Hudson’s mother, Darnell Donerson, 57; her brother, Jason Hudson, 29; and young Julian.

CBS 2’s Mai Martinez reports Cook County prosecutors want Julia Hudson to testify against Balfour, but that might not happen. Jennifer Hudson is also on the witness list, but it is not clear yet if she will be called to testify.

Even though they were estranged, Julia Hudson and William Balfour were still married when he allegedly killed her family, and there are marital statutes which protect communications between a husband and wife that are made in private. That could mean Julia Hudson will not be allowed to testify against her husband.

Jury selection for Balfour’s trial has been scheduled for April 9. Opening statements are expected to begin April 23.