"I don't care if they gave me one second of probation," he said. "I was not signing no paperwork to admit guilt to a charge or to something that I didn't do."
Eventually, the case began to unravel. Pat Andler, who also worked on Caples' defense, told ABC News it's clear the fire started because of an electrical short in the attic of the rental home.
"Again, Sam Richardson got it wrong," Andler said. "He had the origin of the fire wrong. He had the causation of the fire wrong. He claimed that the fire started in the carport area. That's not the case at all."
But the case against Caples truly fell apart when the traces of accelerant Sadie detected came back from the lab negative. Prosecutors dropped the charges against Caples the day before his trial was set to begin. And it turns out the same thing happened in the Sloan case – Sadie found accelerants that the lab did not.
At one point in the video taken by Richardson while on scene at the Sloan fire, Sadie doesn't alert and Andes is heard on the video saying "just fake it for me, OK?"
"This should not have ever occurred," Andler said. "I don't understand why Fred Andes did that and Sam Richardson. I then questioned their ability. I desire to question their character. I certainly question their ethics."
The charges against Barbara Sloan were dropped by prosecutors "in the interest of justice." Sloan filed a civil suit and lost, but is appealing her verdict.
"I think they jumped to conclusions too quick," Sloan said. "I think the main investigator behind my fire did not take the time to properly investigate everything, and I believe he walked in with a very biased opinion and … shaped it to support his findings."
Arson dogs do often find trace amounts of accelerants that can't be confirmed by labs, because they're detecting trace elements too small to be meaningful; too small to help start a fire. According to the National Fire Protection Association, Sadie's alerts should not have been used as evidence to indict Sloan or Caples without confirmation from a lab.
Andes declined ABC News' repeated requests for an interview, citing an ongoing internal investigation that was launched in the aftermath of the Sloan case. Richardson also declined to comment.
Director Jack Ballentine declined our repeated requests for an interview, citing that same internal investigation.
The Phoenix fire investigators continue to stand by their accusations. The findings from a public safety investigation are expected to be released in the coming weeks.