CHICAGO - Jurors in the case of the man accused of killing relatives of Jennifer Hudson began deliberations late Wednesday afternoon after prosecutors trying to counter defence claims of a weak case insisted that "a tsunami of evidence" linked him to the crime.

The defence told jurors during closing arguments that prosecutors had failed to prove that Hudson's former brother-in-law, William Balfour, was the killer. Hudson has attended every day of testimony in the murder trial and was there for closing arguments as well.

The actress and singer bent forward, her head on her knee, and sobbed as prosecutor Jennifer Bagby described what she called "the execution" of the Oscar winner's mother, brother and 7-year-old nephew in October 2008.

Bagby showed jurors photos of the victims' bloody bodies juxtaposed with pictures of them alive.

"This defendant is the one that made (them) into these images," Bagby said, glancing back at the photos.

Closing arguments lasted for about four hours, and the jury didn't begin deliberations until shortly before 5 p.m.

Prosecutors contend Balfour killed Hudson's relatives in an act of vengeance against Hudson's sister, Julia Hudson, his estranged wife at the time. Juila Hudson fiddled nervously with a piece of string as Bagby described how her ex-husband allegedly shot her son, Julian King, whom she called Juice Box, through the head.

Balfour "left that innocent child to die in his own pool of blood," covered by an old shower curtain, Bagby told jurors, who looked on intently, many of them taking notes.

Public defender Amy Thompson started her closing by pacing the room, walking up to Balfour and then toward the prosecution table, angrily pointing at the three state's attorneys.

"They know as they sit there that they have failed to prove the case," Thompson said almost at a shout.

"I am offended," she went on, "that they would ask you to throw your logic away."

Lead prosecutor James McKay told jurors later that the circumstantial facts against Balfour amounted to "a tsunami of evidence ... that is drowning him in guilt."

During her closing, Bagby laid the alleged murder weapon on the podium, the silver and black .45-calibre handgun clanging as it hit the wood. Bagby said gunshot residue from that gun was found on the steering wheel of Balfour's green Chrysler; bullets taken from the bodies were fired from the same gun, she said.

"Make no mistake, there is physical evidence ... linking him to the murders," she said.

She also explained that circumstantial evidence includes everything short of a direct witness.

"Contrary to what you may have heard on television ... circumstantial evidence isn't lesser evidence," she said.

The last word to jurors was left to McKay, whose voice soared as he walked up to the defence table and looked straight at Balfour, a one-time Gangster Disciple who spent nearly seven years in prison for attempted murder.

"Calling the defendant a dog is an insult to dogs!" McKay said.

McKay also lashed out at Thompson, who had finished her closing minutes earlier.

"I don't know what the acoustics are like in this courtroom," McKay said after pointing at Thompson. "But what in the world was she listening to here (during two weeks of testimony)?" he shouted.

Balfour pleaded not guilty to three counts of first-degree murder. If convicted on all counts, he faces a mandatory life prison term.

Prosecutors presented weeks of testimony, starting with actress and singer Jennifer Hudson. She told jurors about the last time she saw her three family members alive and spoke endearingly about her nephew.

The defence called just two witnesses -- two detectives who had testified earlier -- in a bid to suggest investigators botched the triple-homicide investigation.

Prosecution witnesses testified that Balfour threatened to kill the Hudson family dozens of times if Julia Hudson refused to reconcile with him.

Prosecutors say Balfour shot Hudson's mother, Darnell Donerson, 57, in the living room of the Hudson family home on Chicago's South Side on Oct. 24, 2008, then shot Hudson's 29-year-old brother, Jason Hudson, in the head as he lay in bed.

Balfour then allegedly abducted Julian and shot him as he lay behind a front seat of an SUV. His body was found in the abandoned vehicle miles away after a three-day search.