PONTIAC, Mich. -

The defense is presenting its side of the case in the first-degree murder trial of a 75-year-old woman who fatally shot her teenage grandson at their suburban Detroit home.

Sandra Layne took the stand to testify in her own defense. There is no dispute she repeatedly shot 17-year-old Jonathan Hoffman last year at their home in West Bloomfield Township.

On the stand, Layne described the hours that led up to the shooting. She says Jon was angry after he tested positive for K2 during a probation visit. Layne told the courtroom that her grandson was agitated and swearing. She said he was using "street language" as she drove him home from the probation visit. She says Jon kicked the dashboard and grabbed at her car keys. She said Jon was determined to leave Michigan and avoid jail after testing positive for drugs. The argument continued once the pair was home and according to Layne, Jon threaten to take her car and leave.

A visibly distraught Layne described how she went to her bedroom to get her gun. The gun she previously purchased as protection from Jon's friends who would come over to the house at night. She told the courtroom that she approached Jon with the gun in her hand "I wanted him to hear me, that I would not give him the car," she said.

Layne said she approached Jon and they argued. She said Jon kicked her and struck her in the head. "I shot the gun," Layne said.

Layne's attorney says she feared for her life because of Hoffman's erratic behavior and his use of synthetic marijuana.

West Bloomfield police cadet Shelby Maranowski testified Wednesday that Layne held a cold juice box to her face while in a police lockup after her arrest. The testimony was intended to suggest that Layne may have been injured during her confrontation with her grandson.

The prosecution argues Layne followed and fired at the teen several times as he staggered through the home.

Layne looked away from a screen in court that showed photos of bloody footprints throughout the home.

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The blood expert also identified a trail of bloody footprints in the basement. He believes those prints were left by Layne.

The jury already has heard a 911 call in which Hoffman is on the phone for more than two minutes pleading for help before the final shots are fired. A juror asked a ballistics expert, "could an elderly woman repeatedly pull the trigger easily?"

"It is a relatively light trigger pull and I would say that really isn't something that I could nail down and say positively absolutely. The person's physical condition and capabilities are well beyond my realm of expertise," said Shawn Kowlonich, a MSP firearms expert.

According to the testimony, in the weeks before the killing Layne made four separate trips to a gun store to buy the handgun, to practice with it and to correct a mechanical issue with the weapon.

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