A Daviess County Judge sentenced a Washington man to 20-years in prison Tuesday for hitting his 80-year-old grandmother with a rock in September of last year. The Washington Times-Herald reports 34-year-old Christopher Archer received the sentence after pleading guilty to a charge of Aggravated Battery. Four other counts including theft and battery with a deadly weapon were dismissed. Archer told the court he was high on methamphetamine at the time he hit 80-year-old Oneda Cornelius, whom he was living with at the time. He then took Cornelius’ car and purse. Authorities say Cornelius was seriously injured in the attack and remains in a nursing home.