William Balfour was arrested at Stateville Correctional Center and released to detectives as he awaited formal charges in the shooting deaths of the singer and Oscar-winning actress' relatives, said Chicago police spokeswoman Monique Bond.

Until yesterday, police had identified Balfour, 27, only as a "person of interest" in the investigation. He had not been charged by late yesterday afternoon, said Andy Conklin, a spokesman for the Cook County state's attorney's office.

The bodies of Jennifer Hudson's mother, Darnell Hudson Donerson, and brother, Jason Hudson, were discovered October 24 at the family's home on the South Side of Chicago. The body of 7-year-old Julian King was found three days later in a sport utility vehicle on the West Side. All three had been shot.

Police took Balfour into custody the same day the bodies of Donerson and Hudson were discovered. After 48 hours - the longest Chicago police can hold a person without charges - Balfour was taken by the Illinois Department of Corrections on the suspected parole violation.

Balfour - Julian's stepfather and the estranged husband of Jennifer Hudson's older sister, Julia Hudson - served seven years for a 1999 attempted murder and vehicular hijacking conviction.

His mother, Michelle Balfour of Chicago, has denied that her son had anything to do with the deaths. Telephone numbers for Balfour's mother and sister were disconnected yesterday.

Balfour had refused to take a lie-detector test and stopped cooperating with detectives in the case, a police official, who was not authorized to discuss the case publicly and spoke on condition of anonymity, has said.

Police have confirmed they found the gun used in the killings. The .45-caliber gun was discovered October 29 in a vacant lot in the West Side neighborhood where the King's body was found a few days earlier.

Bond declined to discuss any evidence yesterday. But after a hearing at the prison, the chairman of the Illinois Prisoner Review Board said a woman had told authorities that a gun used in the slayings was "identical" to the gun that was recovered.

At the time, board Chairman Jorge Montes said the evidence was key to a decision finding probable cause that Balfour violated his parole and should remain locked up pending a tomorrow hearing before a review board panel.

Balfour did not have an attorney at the November hearing, and the Cook County public defender's office said at the time that nobody from the office had been assigned because he was not formally charged with a crime.

No one in the public defender's office was assigned to Balfour's case late yesterday, and it' was not clear whether he had other representation.