An Alabama woman convicted of murder in the running death of her 9-year-old granddaughter died on Friday, less than a year into her sentence of life in prison without parole, a prison spokesman said.

Joyce Garrard, 50, was convicted last March in the 2012 death of Savannah Hardin. Garrard made Hardin run for almost three hours while carrying wood as punishment for lying about having eaten chocolates.

The girl collapsed and went into seizures, later dying of dehydration and low sodium, prosecutors said.

Garrard was pronounced dead in an Alabama hospital at 5:23 p.m., said Alabama Department of Corrections spokesman Bob Horton. She had suffered a heart attack in prison a few days earlier, said her defense attorney, Dani Bone.

Bone said it had been a difficult time for the family.

"I believe the family is going to be somewhat relieved with the thought that Joyce is going to be in heaven with Savannah and her pain and suffering will be gone," said Bone.

Garrard said in a conversation with Hardin's school bus driver captured on a bus video that "she's going to run 'til I tell her to stop" as punishment. Hardin had a bladder condition and was not allowed to have sweets or caffeine, Garrard told the bus driver.