The somewhat muffled recording was clear enough to hear his November 24, 2007 confession.
Cooper confessed to all the murders, including the death of 48-year-old Ricky High, who according to Cooper, was in the wrong place at the wrong time.
Cooper's own legal team says he did kill five Wake County men between 2006 and 2007, but the question is what his state of mind was at the time.
He's using a defense called "diminished capacity," claiming to have been programmed to kill by a father so abusive, physically and sexually, that Cooper became mentally unstable.
However, prosecutors argue Cooper is a cold blooded killer and they showed the jury dash cam video of a police chase after a Garner bank robbery in late 2007.
The gun Cooper dropped during the chase, matches bullets used in the five murders.
Cooper's confession may also hurt his case, because at times, it appears to suggest premeditation.
At one point in the confession Cooper tells investigators about the murder of Timothy Barnwell.
"I'm a good shot bro," Cooper told authorities in 2007. "I believe I shot him from the balcony."
"After you shot him, what did you do," investigators asked.
"I used a towel to clean out inside the place," Cooper replied.
He also described murdering 40-year-old Leroy Jernigan in July 2006.
"I just shot a dude, that's all," Cooper said.
Jernigan's sister Chastity was among those listening and hardest for her was Cooper's lack of emotion.
How can a human being sit there and just talk about it like … I'm talking to you right now," she said. "When you have a wound the wound kind of covers up, you have the scab and now you're having to pull that scab back off and pouring salt on the wound now, because we're actually able to see him and hear some of the things that were in the audio."
The trial is expected to last weeks. More than 160 witnesses may be called, including psychiatrists and more recordings -- audio and video -- will likely be heard.