MISSOULA, Mont. -

A 19-year-old Billings man has pleaded guilty to deliberate homicide for beating and stabbing his great-grandmother to death during an argument.
    
Robert Alan Thompson entered his plea for the July 19 death of 77-year-old Shirley Lawrence during a hearing before District Judge Mary Jane Knisley on Friday.
    
Prosecutors plan to ask that Thompson get 75 years in prison when he is sentenced on March 27. His public defender is free to argue for a shorter sentence.
    
Charging documents said Thompson was staying and Lawrence's house and killed her during an argument that began when she suggested he get a job or "he was going to be just like his father."
    
Thompson was arrested the next day in Denver while driving Lawrence's car.