PONTIAC (WWJ/AP) – Opening statements have started in the trial of a 75-year-old suburban Detroit woman charged in the shooting death of her 17-year-old grandson.

Sandra Layne appeared in Oakland County Circuit Court Tuesday on first-degree murder and gun charges.

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Defense attorney Jerome Sabbota has said Layne was acting in self-defense on May 18, 2012 when she shot Jonathan Hoffman in the condo he shared with his grandparents in West Bloomfield Township.

Hoffman called 911 after being shot three times and told a dispatcher “I’ve just been shot… My grandma shot me. I’m going to die. Help.” While still on the phone with operators, Layne apparently shot Hoffman again, the sounds of which were captured on the call. A transcript of the 911 call was read in court.

Police arrived on the scene and were greeted by Layne holding a 9mm Glock 17 in her hand.

“She was ordered to put the gun down. The first thing she says to (the officers) is ‘I murdered my grandson.’ Officers take her around the side of the building… she then says ‘I shot, I killed my grandson,'” said prosecutor Paul Walton.

Meantime, other officers looking through the home trying to locate Hoffman found pools of blood.

“The officers literally followed a blood-trail upstairs into the loft where they find 17-year-old, 5-foot-six, 110 pound Jonathan Hoffman laying next to his couch, dying. He is dressed only in a pair of athletic shorts and athletic socks. Later, an autopsy will show that he has been shot six times,” Walton told the court.

There’s no doubt that Hoffman’s 911 call is a critical part of the case, but WWJ Legal Analyst Charlie Langton says the defense is zeroing in on a different 911 call.

“Sabbota played a 911 call of about a month before the murder that was made by the grandmother, complaining to the police that she was afraid of her grandson. And that, the jury actually heard the actual 911 tape,” said Langton.

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In that incident, officers say they were called to the home on March 21, 2012 on a report by Layne that Hoffman was upset and yelling. Layne frantically tells the 911 operator that Hoffman is very upset and is threatening to run away. Several times during the call, Layne stops talking to the operator to speak with Hoffman.

“Because I love you and I want to see you get some help. Who else can I call?” Layne can be heard telling her grandson. “I know you hate me… but we need to get you some help… (I called 911) because I was desperate and I didn’t know what to do. I was desperate.”

Sabbota said it was after this incident in March that Layne bought a gun.

In addition to his violent outbursts, the defense claims that Hoffman had issues with drug use. Sabbota pointed to toxicology results which show that Hoffman’s urine tested positive for traces of synthetic marijuana, although no traces were detected in his blood. The findings imply that Hoffman was not under the influence at the time of his death, but had used the synthetic drug in the days prior.

“There are many factors which caused the shooting … I’ve always said that,” said Sabbota. “The K-2 or the Spice is part of it … part of it that he tested positive on that day for K-2 with the probation department, positive that he was angry, positive he was worried about going to jail — all part of it.”

Hoffman was on probation after drug-related run-ins with the law and was attending an alternative high school for troubled kids. He was living with his grandparents so he could finish up his senior year after his parents, who are divorced, moved to Arizona. Hoffman’s father, Michael, has said he and his ex-wife were not aware of problems between the teen and his grandmother.

The trial is expected to last about two weeks.

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