Margaret's daughter beat her to death, then set their shared apartment on fire to conceal her crime.  When firefighters arrived, she told them that her mother had accidentally started the blaze with a stray cigarette.  Forensic analysis proved her version of the events to have been impossible, however, and the autopsy revealed Margaret's injuries and the fact that she was already dead when the fire began.  Her killer was convicted of arson and second-degree murder and sentenced to 15 years to life.