"You know, the state's Fire Marshal's Office told me that there was gas poured everywhere out there," Sandoval later told ABC. He admitted, however, that the fire marshal had not told him that gas was poured on the kids.
"Sometimes you've got to do what it takes to get to the truth," he said.
But the truth might very well have been destroyed, because on the day after the fire, investigators had the house bulldozed.
"That wasn't my doing," said Sandoval. "That was the state fire marshal's call. I know now that wasn't the right way to handle it."
Meanwhile, as the audio of the interrogation reveals, Kelley kept insisting that she was innocent, even begging to take a lie detector test.
"Can I please go take the polygraph?" Kelley says. "You human beings don't believe ... this could show that at least I'm telling the truth."
But officials never gave Kelley the test. Instead, the case went forward, based on the notion of spalling.
We asked Amanda Kelley if she started the fire.
"No," she said. "Absolutely not. I've stood by my innocence from day one. ... I knew that I was in the presence of a bunch of people wanting to be Horatio on "CSI," and they were really a Barney Fife ... seriously."
ABC News explored how spalling works at Combustion Science and Engineering, Inc., a lab in Columbia, Md., that specializes in the chemistry and physics of fire behavior.
Doug Carpenter, vice president and principal engineer at the lab, showed us concrete with spalling. It was rough and pockmarked.
Then he showed us what happens when gasoline is actually poured on concrete and set alight.
"One of the things you can see is, you can see the liquid boiling," said Carpenter. "The temperature will never get any higher than the boiling point of that liquid underneath it. So the liquid actually acts to protect the concrete."
Instead of producing spalling, the exact opposite happened. The gasoline-fed fire left the slab charred but completely smooth.
"You can clearly see that flammable liquids alone will not produce spalling of concrete," Carpenter said.
We asked John Lentini, one of the nation's leading fire experts, why more fire investigators weren't current on the science of fires.
"It's not a culture that you learn stuff this way," Lentini said. "You learn from your daddy, who learned from his daddy. The belief system of your mentor is just handed down."
In Kelley's case, those dominoes of outdated beliefs kept falling, right into the hands of the district attorney's office. A Louisiana district court would eventually call the spalling evidence an "old wives' tale."
But for Kelley, vindication was still a long way off.
The Kelley story generated a tidal wave of accusations. From the start, almost every day brought another newspaper story and another rumor: Amanda never tried to save her children. The kids were found bound and doused with gasoline.
Meanwhile, Kelley sat in the Alexandria jail, awaiting trial on charges that could carry the death penalty. Mike Small, one of Louisiana's most well-known defense lawyers, took on her case.
Small said the atmosphere surrounding the case was poisonous.
"There is no credible evidence that she set the fire," Small told ABC. "None. ... Defending Amanda was almost like defending Satan."