PONTIAC— Jurors have been to sent to deliberate in the historic trial of the mother of the Oxford High School shooter and whether she should be held criminally responsible for the 2021 shooting that left four students dead. Jennifer Crumbley faces up to 15 years if she’s convicted and her case in Oakland County Circuit Court marks the first time a parent has been tried for manslaughter in connection with a mass shooting. Experts said it could set a precedent for parents being held responsible for their children’s actions. During her instructions to the jury Monday, Judge Cheryl Matthews instru…