The formal charges against Balfour were announced Tuesday in the deaths of Hudson's mother, brother and 7-year-old nephew.
Balfour has been in custody for a parole violation since October, when the bodies of Hudson's mother, Darnell Hudson Donerson, 57, and brother, Jason Hudson, 29, were discovered. Three days later, Hudson's young nephew, Julian King, was found dead in the back of an SUV.
Balfour was supposed to appear before the parole board at the Stateville Prison Wednesday, but he is now in custody at Area 1 police headquarters. Police say the timing of the charges has nothing to do with with the parole hearing.
Balfour was also charged with one count of home invasion. Police say they believe the three victims were killed on the same day in a domestic dispute and that Balfour acted alone.
"My son did not do this. I'm sick of this. They need to focus on somebody else," said Michele Davis-Balfour, William Balfour's mother.
William Balfour's mother rushed to Area 1 police headquarters Monday night, telling reporters her son did not kill Jennifer Hudson's three family members.
Police have been focusing on the 27-year-old since the investigation began October 24, the day Jennifer Hudson's mother and brother were found shot to death inside their Englewood home. Three days later, the body of Hudson's nephew, Julian King, was found on the West Side. Police believe he was shot and killed inside the vehicle.
"If they found a gun on him, they had a case. If they found a fingerprint on the truck that he did this, they have a case. But you don't have nothing," said Davis-Balfour.
Two days after King's body was discovered, police found a .45 caliber handgun they say is the murder weapon in some bushes near where the SUV containing King's body was found. The Sun-Times reports that the gun is believed to have belonged to Jason Hudson.
All along, police have called Balfour a "person of interest." They say the Hudson family and Balfour's girlfriend have been cooperating with investigators.
"I know a lot of people beginning to doubt, 'Was it this guy? Maybe it's a killer walking amongst us. I guess it is in a sense--it's a relief, a big relief," said Charles Ousley, Hudson family friend.
But Balfour's attorney says police do not have a case.
"Any evidence pointing to Mr. Balfour is not even fit. It is very, very weak," said Joshua Kutnick, Balfour's lawyer.
"There is no direct evidence. There is a big difference between direct evidence and circumstantial evidence. Circumstantial evidence is perfectly good and perfectly good to convict someone of a crime in this state. However, direct evidence, someone seeing him directly doing this, we don't have," said Thomas Glasgow, Criminal defense attorney.