Amanda Brumfield - Thornton's 32-year-old daughter from his marriage to first wife Melissa Gatlin - was arrested in May 2009 following an incident the previous October (08), when one-year-old Olivia Garcia fell from a playpen and hit her head.
The tot's death was ruled a homicide and Brumfield was charged with a number of crimes, including first-degree murder, aggravated child abuse and aggravated manslaughter.
During her trial last month (May11), prosecutors alleged it was impossible a fall would have caused Garcia's skull injury and on Friday (27May11), Brumfield was found guilty of aggravated manslaughter of a child, according to the State Attorney's Office.
Brumfield was found not guilty of first-degree murder and aggravated child-abuse charges.
She is expected to be sentenced in July (11).