Hannah says she started noticing that Andrew was hoarding food, stealing off the other children's plates and throwing tantrums after meal time was over. At times, they say, they caught him trying to eat things that weren't even edible.
"Anything that he found, he would try and put in his mouth. He would also eat the cat food, the dog food, out of the trash can," Hannah Overton told "20/20."
The Overtons believe this unexplained behavior might have been linked to Andrew's death.
"Something was wrong with Andrew. I don't know exactly how or what happened to him," Hannah Overton said. "Something caused his sodium levels to rise, and it wasn't me."
While Hannah and Larry Overton awaited separate trials, Hannah Overton gave birth to a baby girl named Emma. Child welfare services placed all five Overton children with loved ones, allowing the couple only supervised visits.
From day one of Hannah Overton's trial in August 2007, the prosecution portrayed her as a mother who had lost control. Frustrated with a naughty child, prosecutors said, she tried to punish him with seasoning mixed in water and then neglected to get him medical attention, knowing that he was dying.
Detectives questioned why Hannah Overton hadn't called 911, instead driving Andrew to the hospital. One doctor calculated that it would take at least 23 teaspoons of creole seasoning (equivalent to 7 teaspoons of salt) to get Andrew's sodium level as high as it was when he arrived at the hospital.
Medical staff from the hospital also took the stand, testifying that they noticed bruising and scratching on the child's body when he arrived at the hospital. Prosecutors speculated these marks could be signs of abuse, or a struggle.
"Could it be that you held his nose, held his neck and made him drink this horrible concoction?" prosecutor Sandra Eastwood asked at trial.
"Absolutely not," Hannah Overton testified.
The prosecution also countered claims by the Overtons about Andrew's strange behavior. Witnesses, including Andrew's former foster mother Sharon Hamil, took the stand and told jurors the boy seemed perfectly healthy and never exhibited odd or excessive eating.
"Andrew was not a difficult child to take care of," said Hamil. "At least he was not when he was with me."
The defense presented the jury with a medical mystery. They speculated Andrew might have had Pica, an eating disorder characterized by an obsessive appetite. Witnesses outside the home had seen Andrew's bizarre habits too.
Hannah Overton told jurors that she thought the behavior was unusual, but had learned in adoption classes that children in foster care often exhibited issues with food.
When the problems escalated, she alerted Andrew's adoption agency. During the visit to the home, the caseworker mentioned Pica as a possible explanation.
Hannah said it was just a few days later that Andrew got sick and eventually died. She said she believes he may have gotten into something that morning when she wasn't watching that caused his sodium levels to rise.
Hannah insists the creole seasoning mixed with water wasn't to punish -- it was to soothe Andrew's insatiable appetite.