Updated 04/30/12 – 7:15 p.m.

CHICAGO (CBS) — Prosecutors continued to build their case Monday in the trial of the man accused of killing three members of singer Jennifer Hudson’s family, including the first testimony that Hudson’s 7-year-old nephew was killed in his uncle’s stolen SUV, not the Hudson home like the other two victims

William Balfour, now 30, is accused of killing Hudson’s mother, Darnell Donerson; her brother, Jason Hudson; and her nephew, Julian King, on Oct. 24, 2008. Prosecutors have said Balfour, the ex-husband of Hudson’s sister Julia, killed the victims in a jealous rage, believing Julia was dating another man.

Although prosecutors have said all three victims were killed on the same day, it wasn’t until Monday that testimony revealed Julian was apparently killed inside Jason Hudson’s SUV, which Balfour allegedly stole after killing Jason and Donerson.

Chicago Police forensic investigator Raymond Jaster testified that Jason’s SUV was located three days after the murder when a West Side couple noticed it had been parked near their house for three days.

Jaster said he was called to 1313 S. Kolin on Oct. 27, 2008, and, when he looked inside Hudson’s SUV, he saw Julian’s body on the floor of the rear seat, covered in a shower curtain..

“When I looked inside the vehicle I saw a body in the back seat,” he said.

Because the discovery of the stolen SUV had drawn a large crowd of onlookers, as well as a throng of reporters and news helicopters, police decided to have the SUV towed to an auto pound to process it for evidence.

RELATED: Hudson 911 Tape: “Somebody Killed My Mama!”

Once at the auto pound, Jaster found a shell casing next to Julian’s hand and discovered the boy had been shot in the head – apparently while inside the SUV. There was a pool of blood under Julian’s body and an apparent bullet hole through the floor under him.

Prosecutors also showed the jury photos of Julian King’s body inside the SUV and, as they did when other graphic photos were shown in court, Jennifer Hudson and her sister Julia left the courtroom to avoid seeing the pictures.

Jaster said, while processing the SUV for evidence, investigators swabbed the entire vehicle for DNA and collected gunshot residue from the headliner and other parts of the vehicle. They also removed the cloth covering from the driver’s seat to check it for DNA.

Jason Hudson’s state ID card and several empty soda bottles were also found on the floor of the SUV.

Earlier in the day, Chicago Police Officer Terrence Fowler, who was a new police recruit at the time of the killings, testified about finding the alleged murder weapon less than a block away from where the SUV was found.

Fowler was assigned to a search team tasked with looking for physical evidence two days after police located the SUV.

Police Sgt. William Svilar had earlier testified that he assigned a team of 90 police recruits, including Fowler, to assist in that search. Svilar split the team into two groups to search for evidence along a path between where the SUV was found and the location where Balfour had been arrested on Oct. 24, at 1925 S. Spaulding — his girlfriend’s home.

One group started at Spaulding and the other started at Kolin, then gradually worked toward each other, searching every vacant lot, vacant building, alley, garbage can and other open space along the way.

Fowler was searching a vacant lot less than a block from where the SUV had been found, using an expandable metal baton to sift through grass and debris, when he heard a clinking sound. When he cleared away the grass and debris around him, he saw a .45 caliber handgun on the ground.

According to Fowler, other officers conducting the search tried to get a closer look at the gun before forensics teams arrived, but he kept them away, telling the jury “this was a crime scene.”

Svilar, who was overseeing the search, testified he helped Fowler secure the scene until forensics teams could process the evidence. According to Svilar, the gun found in the lot was a .45 caliber Sig Sauer semiautomatic handgun. That is the gun that prosecutors have said was used in the slayings, after Balfour allegedly stole it from Jason Hudson earlier the same year.

Jurors also heard from the police officer who found Balfour’s green Chrysler outside Robeson High School on the day of the murders, about a half mile from the murder scene.

Police processed the car for evidence that same day, and later recovered a surveillance video from the school.

Jurors were also told about how investigators collected DNA and fingerprint evidence from Balfour; the bullet from Jason Hudson’s skull; blood, fingerprint evidence and DNA from all three victims; and the effort to find fingerprints at the murder scene, although a forensic investigator said there were no useable prints at the Hudson home.

Balfour, an alleged drug dealer, has denied any involvement in the killings and his attorneys have noted that DNA evidence collected from the murder weapon does not match Balfour. DNA and fingerprints taken from the stolen SUV also does not match the defendant.

The defense has suggested that the killings might have been linked to Jason Hudson’s own drug dealings.

The trial is expected to last two to three more weeks. Much of the upcoming testimony likely will revolve around the police effort to gather physical evidence that, while crucial, won’t carry the emotional weight that Jennifer and Julia Hudson provided about the victims, or of Balfour’s alleged confession to his girlfriend, which jurors heard about on Friday.