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.
"My thought was that I would calm him down, appease him, give him like a broth, without giving him a tummyache from eating more food," Hannah told "20/20."
When asked why she didn't get him help sooner, Hannah said, "We didn't know that there was anything major going on. We didn't realize how sick he was. … If we had known that there was something more going on, we would have rushed to the hospital."
But Hannah Overton was convicted of capital murder and sentenced to life in prison in September 2007.
"I just kind of broke down," Larry Overton said. "And I just stared out a window for ... I don't know ... probably about an hour."
To find Hannah guilty, jurors had to believe either of two scenarios -- that Hannah force-fed Andrew Burd salt knowing it would kill him or that she neglected to get medical help fast enough knowing that that would kill him.
All 12 jurors agreed with the second scenario, and "20/20" spoke to two of them.
"I don't believe it was her intention to, to kill him," said juror Dora Santos. "I just feel that if Andrew would have gotten help sooner he would probably be alive today."
"I mean, she killed him because she didn't seek medical help," said juror Norma Bejarano.
But when asked if Hannah Overton intentionally withheld medical attention from Andrew in order to kill the child, Santos replied, "That's something we'll never know."
Two doctors, both experts in the case -- one for the prosecution, the other for the defense -- believe Hannah Overton was wrongly convicted, and they spoke on camera for the first time to "20/20."
Dr. Edgar Cortes, the same pediatrician who treated Andrew at the emergency room and later consulted for the prosecution, said he always believed Andrew's death was accidental. Cortes is not being paid by the Overton defense team.
"I was stunned when I heard that [Hannah] had been given capital murder. I was just at a loss for words," Cortes said.
Cortes disagrees with the prosecution's portrayal of Andrew as perfectly healthy -- he said he saw speech and developmental problems back in 2005.
"The only physician that treated Andy while he was alive, and who was aware of the other neurological problems that he had, was me," Cortes said. "And I think that testimony might have given the jury an understanding that perhaps he was not a totally normal child."
But neither the defense nor the jury ever heard Cortes' opinions, which are the cornerstone of Hannah's appeal.
Prosecutor Sandra Eastwood said she doesn't recall Cortes expressing doubts about Hannah's intent.