By Verna Gates

BIRMINGHAM Ala. (Reuters) - An Alabama woman accused of running her 9-year-old granddaughter to death as punishment for eating forbidden chocolates and lying about it was set to go on trial on Monday.

Joyce Hardin Garrard, 49, stands accused of forcing Savannah Hardin to run non-stop for three hours in February 2012. Authorities say the girl collapsed, went into seizures and died days later at a Birmingham hospital.

Hardin died from dehydration and low sodium, a condition common in marathon runners, Etowah County Sheriff's spokeswoman Natalie Barton said.

Hardin suffered from unspecified medical issues that resulted in frequent doctors visits, according to court documents.

Defense attorneys have said that it was the girl's medical condition, and not the punishment, that caused her death.

Hardin's stepmother, Jessica Mae Hardin, is also charged in the case, with witnessing the punishment and failing to intervene.

Defense attorney Dani Bone did not immediately return messages seeking comment.

The girl lived with her father, whose mother is accused in her death. He frequently traveled for work and was out of town at the time of the incident, authorities said.

A third grader, Hardin was a successful student, said Alan Cosby, superintendent of the Etowah County Schools.

"She was a very pleasant, nice young lady," Cosby said.

(Editing by Jonathan Kaminsky; Editing by Ruth Pitchford)