Jennifer Hudson's sister, Julia, celebrated turning 31 on Oct. 23 with cake and a small party at home.

The next morning, police say, Julia's estranged husband William Balfour – booted last February from the house on Chicago's South Side where they lived with Julia's mother and 7-year-old son – showed up and spotted a gift he believed came from another man.

That jealousy is the motive that led Balfour, 27, to return to the house after Julia had left for work and shoot her mother Darnell Donerson, 57, Jennifer's brother Jason, 29, then take Julia's son, 7-year-old Julian King, and later kill him as well, prosecutors allege.

Jennifer and other Hudson family members were "relieved and happy" after Balfour was charged Dec. 2 with three counts of first-degree murder and one count of home invasion, Chicago Police Deputy Superintendent Steve Patterson has said. Those family members assisted "every step of the way under very stressful and painful circumstances," adds police Superintendent Jody Weis.

Balfour's attorney Joshua Kutnick says the stormy relationship between Balfour and Julia Hudson makes his client a convenient target.

"We are extremely confident that once all of the evidence has come to light and has been tested by our vigorous analysis of the case, that William will be found not guilty," Kutnick said after a judge ordered Balfour held without bail.

A Growing Tension
But the revelation that gunpowder residue turned up in Balfour's green Chrysler "is indicative that he fired a handgun," Cook County Assistant State's Attorney LuAnn Snow says. "So yes, indeed, there is physical evidence."

In detailing their case against Balfour, prosecutors described a growing tension between Balfour and Julia Hudson.

In early October, Balfour confronted Julia at her workplace. He accused her of dating another man and threatened her family if she continued, Cook County Assistant State's Attorney LuAnn Snow said during the bail hearing.

Julia dismissed him because Balfour hadn't acted on earlier threats to her family, Snow told Cook County Circuit Judge Raymond Myles.

Morning of Murders
On the morning of the murders, Balfour went to the Hudson home in Chicago's struggling Englewood neighborhood, where Jennifer grew up singing in the church choir, and where her success and Oscar win are a source of community pride.

That's where Balfour saw the birthday gift that he attributed to Julia's alleged boyfriend and warned her again, Snow said.

Both left around 8:10 a.m., when Julia went to work as the three victims slept.

Balfour told detectives he went home on the train using a public transit card. But the card wasn't used that day, Snow said, and Balfour didn't turn up on security video taken at the train station. Instead, cell phone records place him near the Hudson house until about 9 a.m., by which time authorities say both Donerson and Jason Hudson had been killed. Donerson was shot in the living room. Jason was shot while still in bed.

Forensic Evidence
Balfour moved his own car from the home before driving away in Jason's white Chevrolet Suburban with Julian inside, Snow said.

The timing of Julian King's death is still in question – his body was found three days later in the back seat of Jason's missing SUV, parked on a west side street several miles away – but police believe Julian was shot in the vehicle the same day as the first two murders.

Forensics tests later matched a .45 caliber handgun found in an alley near the parked Suburban with shell casings found at the house. And prosecutors said the gun belonging to Jason Hudson had been stolen by Balfour last summer and seen by Balfour's girlfriend, to whom they say he admitted his role in Donerson's and Jason Hudson's deaths.

A "Viable Case"
Balfour has been in custody since the day of the murders. He subsequently was transferred to a state prison for a suspected parole violation – he served seven years on a 1999 conviction for attempted murder and carjacking – and was returned to police custody after his arrest in the Hudson slayings.

"At this time," said police Deputy Superintendent Peterson, "it doesn't appear that anyone else was involved."

"He's not confessed to these crimes," said police Superintendent Weis. He added, "You never know how a jury is going to decide cases, so whenever you go to trial, it is somewhat a roll of the dice. But I am confident that the evidence has been collected, the testimony that's been secured is strong, and I think we can make a very viable case in court."