By Joseph A. Slobodzian, The Philadelphia Inquirer

Toni Nelson listened to the sound of her voice making the 911 call and seven years evaporated.

Tears ran down her cheeks, her hand covered her mouth as the 911 audio tape intoned “June 15, 2008, 1:28.46 a.m.” and then Nelson’s voice: “I heard a big bang and he’s down. There’s a man lying on the sidewalk in front of my house.”

So began testimony Wednesday in the trial of Marcellus Jones, charged with slaying 23-year-old Minnesota teaching student Beau Zabel to take his iPod.

Nelson, who then lived at 828 Ellsworth St. in South Philadelphia, testified about that “boom” seven years ago that she said she assumed was an exploding utility transformer on the corner.

“We had problems with the transformer before,” Nelson told the Philadelphia Common Pleas Court jury of 10 women and 2 men.

But the moment Assistant District Attorney Jacqueline Juliano Coelho played the audio from Nelson’s 911 call, the witness seemed to go into a trance.

Defense lawyer Richard J. Giuliani asked if she recalled the time of her 911 call. She couldn’t. He reminded her that it was on the audio recording of the call.

“I wasn’t paying attention,” Nelson replied. “You have to understand, I’m right back there again. I’m in my pajamas.”

On the audio tape, Nelson is heard describing Zabel for the police dispatcher and adding, “He’s still down. He’s not moving.”

Seconds later: “There’s another guy out there, he’s looking for a bullet. Oh God, he’s searching for something out there.”

Nelson testified that she watched the scene peeking between the slats of venetian blinds in her second-floor bedroom. But, questioned by Coelho, Nelson said she could not remember anything about the second man except that he searched for something around Zabel’s body and then walked away toward Ninth Street.

Jones, 37, of South Philadelphia, is charged with tailing Zabel that night as the Drexel teaching fellow walked home after his shift at a Starbuck’s at Ninth and South Streets.

Zabel was a teaching fellow enrolled at Drexel University where, in October 2008, he would teach during the day and take evening courses at Drexel towards his certificate.

In the interim, Zabel got a job at a Starbuck’s on South Street. Zabel had lived in Philadelphia just six weeks on June 15, 2008 when he was shot and killed about one block from his house.

No physical evidence will link Jones to the shooting and for years, Zabel’s slaying was considered a cold case.

Coelho and fellow prosecutor Tracie Gaydos told the jury Marcellus Jones’ incriminated himself through indiscreet admissions to friends and relatives that he was the one who shot Zabel in the back of the neck early that morning.

Jones is serving a life prison term without parole for his 2012 murder conviction for shooting Tyrek Taylor, 19, of South Philadelphia.

Prosecutors say Taylor drove the getaway car for Jones the night Zabel was killed and later told relatives he killed Taylor because he was talking about Jones “killing the teacher.”

Giuliani has argued that the prosecution case is built from statements incriminating Jones, made years after the fact, from people desperate to earn favorable treatment from prosecutors and escape long prison terms.