Todd Mcinturf / The Detroit News via AP Sandra Layne is shackled after she was convicted Tuesday, March 19, in Pontiac, Mich., of second-degree murder in the shooting death of her grandson last year.

A 75-year-old Michigan woman was convicted of second-degree murder charges Tuesday for shooting her 17-year-old grandson to death last year.

Sandra Layne of West Bloomfield, northwest of Detroit, was held without bond pending a sentencing hearing April 18, NBC station WDIV of Detroit reported.

In addition to the murder charge, Layne was also convicted of possession of a firearm in the commission of a felony in the shooting. Oakland County Prosecutor Jessica Cooper told WDIV that Layne was likely to face 12 to 20 years in prison for the murder conviction, plus two years for the firearms violation.

Jurors were given the option of deciding whether Layne committed first-degree murder, but they chose the lesser charge.

The death of Layne's grandson, Jonathan Hoffman, on May 18, 2012, made national headlines after it was disclosed that he was shot in the chest multiple times as he was calling 911.

Jurors were played audio of the 911 calls, in which Jonathan frantically told a dispatcher that he had been shot by his grandmother and was going to die. Although investigators previously said they found eight entry and exit wounds in his body, prosecutors said Monday during closing arguments that he was actually shot 10 times.

Layne, who took the stand and admitted having shot Jonathan, said she had bought a gun to protect herself because her grandson sometimes brought strangers home late at night to the condominium unit they shared. She said she felt threatened and shot Jonathan in self-defense after he demanded her car and $2,000 so he could leave the state.

Jonathan's parents are divorced, and his father has previously said his son was living with his maternal grandparents while he finished classes at an alternative high school in nearby Farmington.

Jerome Sabota, Layne's attorney, told jurors in closing arguments Monday that Jonathan had a violent temper and that he used synthetic marijuana.

"Think about somebody that's 73 or 74 and this behavior is occurring in her presence," Sabota said. "She was in hysteria. She was afraid and reacted to his physical attack. That's why killed him. That's why she shot."

But Assistant County Prosecutor Paul Walton said in his closing arguments that Layne never complained of injuries and told police when they arrived at the home that she had killed her grandson.

"The first thing that she says to (the police officers) is, 'I murdered my grandson,'" Walton said.

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