On Thursday afternoon, Cook County prosecutors also linked him to the stabbing murder of another person following an argument in 2019, although there are few details known about that killing.
Turner's body was found by a garbage collector in an alley trash can in the 7300-block of South Kenwood Avenue in March 2017.
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She had been reported missing by family and had last been seen leaving Red's Lounge on South Stony Island Avenue. An autopsy concluded she had been beaten to death with a large hammer and dumped in the alley.
Turner's family has since released secret recording to the I-Team, where Hilliard gives a vivid description of the crime.
"I'm going to give you the whole story. I ain't never seen anything like this in my whole life expect on TV," Hilliard is heard saying on the recording.
Hilliard didn't know he was being recorded in 2017 when he talked about the day his girlfriend, Turner, died in his apartment. He even included where to find the weapon that was used.
"Just open the basement door. You're going to go to that corner, right behind that is the murder weapon. A big (expletive) sledgehammer," he said.
Despite having the recording, police said they needed the DNA results to charge Hilliard.
"He was the primary suspect and the return of the DNA is what took so long," CPD Interim Superintendent Charlie Beck said. "Ya know, we don't have full ability as in some police departments to analyze our own DNA so we have to rely on the state as soon as the DNA came back the warrant was served."
Even though Hilliard is now behind bars, Turner's loved ones say the DNA delay was inexcusable.
"I feel like they need to hurry up and get a better system with their DNA because this shouldn't take three years before he gets charged," said Latonya Turner, the victim's aunt.
The I-Team talked to Hilliard in 2017 when he blamed one of his roommates for the sledgehammer murder. He also claimed he'd given Turner's family enough information "to get street justice."
I-TEAM REPORT: Justice for Diamond Turner
Although she is still mourning her daughter after nearly three years, Turner's mother said she hopes Hilliard is gone for good.
Hilliard, 52, and a father of five children, has been charged with one count of first degree murder. As first reported by the I-Team, he was taken into custody Wednesday afternoon.
He was a career criminal with a lengthy record, and continued to commit crimes during the time he knew that he was a suspect in the Diamond Turner case.
As police waited for the crime lab, a year and a half after Turner's murder, Hilliard was involved in another homicide of Andra Williams. Hilliard ended up pleading guilty to concealing the homicide of the man on the West Side, and was soon free again. That victim had been stabbed to death and left in a shopping cart in September, 2018. Hilliard was sentenced to less than a year in jail for the concealment.
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Thursday prosecutors announced that they now suspect him in a third murder. He is now accused in a 2019 stabbing attack of another person during an argument. Hilliard has not yet been charged in that case.
"If he went to jail March 3 when we told them that he killed Diamond and we got all the evidence, he wouldn't have gotten the chance to kill these extra two people," Latonya said.
The arrest of Arthur Hilliard was met with relief by Diamond Turner's loved ones.
"We're great. We're glad that he's in jail. It's been three long years of us waiting for them to arrest him for her murder," said Latonya. "That's a long time for somebody to be out and about, doing what they're doing and your loved one is gone. You will never see that person again but he's out living his life and probably the same thing he was doing before, probably going to harm somebody else and he's just out and you are sitting at home waiting on the police to call to say they got him, waiting to say they are charging him with her murder. That's stressful."
Cook County Associate Judge Mary Marubio denied bond for Hilliard in the first degree murder case-noting a blood trail from his apartment and a witness who allegedly saw Hilliard cleaning the hammer he is believed to have used in the fatal attack on Diamond Turner.
Turner's family tells the I-Team, "It's been 3 long years of agony and pain for our family. But justice is finally about to be served. Our family can now be at peace. We will never get Diamond back but at least now we have closure. Diamond was sweet as pie and would do anything for anyone so for him to do her like that was senseless. We will always live and remember Diamond and she will always live through her family!"