Tonight, a new development may bring an end to the top of this group. The Phoenix arson squad was the most successful in the nation but a "Nightline" investigation brought up questions on their arson... See More
Tonight, a new development may bring an end to the top of this group. The Phoenix arson squad was the most successful in the nation but a "Nightline" investigation brought up questions on their arson arrests. Did the investigators go too far and did innocent victims pay the price? Here is ABC's Byron Pitts. Once the investigator gets there we take over. Reporter: This is captain Sam Richardson. It is too far today. Reporter: They are investigators with the Phoenix fire department's elite arson squad. The best of the best. And they have the Numbers to prove it. The squad solved more cases in the arson unit than anywhere in the country. We can go into a structure and be able to start anywhere. To a lay person they just look at you like how do you know that? Reporter: But did that success come at a price? I was going to prison for the rest of my life for a crime I didn't commit. Reporter: Tonight, two people who say they were falsely accused of arson, alleging incompetent actions. You were in jail for 16 months? It ruined my life and I'm still paying for it to this very day. Reporter: But our story begins in 2009. ABC news was given extraordinary access to this elite unit. So we could see for ourselves what made them the best in the nation. Captain Andes was proud to admit he had a secret weapon. This is a detection k-9. Reporter: She is commonly used in arsons, highly trained. But there was another force at work, the unit's new controversial director, jack Ballantine, a highly decorated police detective. My job is to make sure that they can realize success on every one of the cases that they go on. Reporter: Between Ballantine's leadership and Sadie's nose, the clearance rate went up. But the record was about to be called into question. Phoenix 911, where is the emergency? There is a fire -- Hold on, I'll put you through to the fire department. Reporter: May 13th, 2009, the home of Barbara slade was on fire. This is the back of the house, you can see we had a pretty good fire here. Reporter: In this video filmed by Richardson, tell tale signs of arson around the house. The glass was around the drier, the iron plugged in. Reporter: There was a date detectdete detected accelerant around the house, but one problem, Barbara Sloan says she didn't do it. Are you an arsonist? No, I was being framed for a crime I didn't commit. Reporter: Sloan was charged with arson and faced 29 years in prison. I sat down with my family and prepared my son and my daughter that their mom is going to jail for the rest of her life. Reporter: For her defense, Sloan enlisted a certified fire investigator with 30 years of experience. When you first looked at the evidence, what was your reaction? Overwhelming, it was clearly a fire that started in the garage. There is a fire in the garage. The garage is completely engulfed. Reporter: He says all the physical evidence pointed to one of Sloan's c??-rs. A Toyota corolla model that had been recalled for defects, including cracks that he believes sparked an electrical fire which then spread throughout the house. Sam Richardson never even entered the garage. So you think this was fire investigation 101. This was below fire investigation 101. This is kindergarten fire investigation. Reporter: But the Sloan case is not the only one. Building on fire. Reporter: Just six days prior, Richardson and Andes were called to another fire, Richardson made up his mind on the scene. So this will be an arson fire, with a possible suspect. Reporter: The suspect was a former sheriff's deputy in the house, he was behind on his rent and had been fighting with his roommate. He had not been paying his rent, they were fighting, he came back and got mad. I saw him prior to the fire. Reporter: Part of the suspicion was you were trying to kill your roommate. Correct. Reporter: Any truth at all to that? None of that. Reporter: Richardson took on the role of interrogator. I got three points, somebody poured this. The dog is hitting everywhere. It was enough to arrest capos and keep him in lock-up for six months. But then the case fell apart. The parts that they said Sadie alerted to? No evidence. The prosecutors dropped the charges. And back in the Sloan case turns out the same thing happened. Sadie found accelerants that the lab did not. Why did Sadie get it wrong both times? Listen to the possible reason why. There is a stunning comment that is made. Please fake it for me, okay? Fake it. Those words were unbelievable. I could not believe what I was hearing in his tone of voice. It was not just a joke. Better? Show me. I was shocked. I don't understand why Fred Andes did that. Said he hit on the dining room. She also hit in the kitchen area right by the stove for it looks like the presence of igniteable liquid. Reporter: Prosecutors dropped the case against Sloan, in the deposition, captain Richardson admits he made up his mind before he had all the facts. I knew when I left that day this was an arson. Before you got any lab support back, right? Yes. Reporter: Then it was captain Andes' turn, he was grilled about the statistics. Do you keep those statistics? No. Why not? I believe she is far superior to what the labs can do. You have no idea how accurate? 99% of the time. How does this strike you? It is absurd to think that a 6-year-old lab is smarter than an individual that has a college degree in chemistry. Reporter: It is true, arson dogs often find trace amounts of accelerants that can't be confirmed by labs. That is because they're detecting trace elements too small to be meaningful. Too small to start a fire. So according to the national fire protection agency Sadie's alerts should never have been used to indict Sloan or capos, we wanted to interview him but he declined an interview citing the investigation by the Phoenix department of public safety launched earlier this year. When we showed up at his house he didn't have much to say. I can't talk about the investigation. Reporter: Actually we talked to the investigators -- The person I can't trust is the media. Reporter: Sir, why is that do you think? But Andes did tell us something back in 2010, something in hindsight that could tell us a lot. We used to think we have to have concrete evidence, and now we can put a case together with circumstantial evidence and make it stick, time and time again. Reporter: His boss declined an interview as well, citing internal investigation. When we caught up with him? Good morning, fire marshal, Byron pits from ABC news, can we talk to you about the investigation? I take it the answer is no. Reporter: Just last month, the results of the investigation were finally released. The department of public safety recommended charging Richardson with six counts of false swearing and Andes with one, all felony counts in Arizona, no charges against Ballantine were recommended. Although all were placed on assignment. Up next for us, show me the
This transcript has been automatically generated and may not be 100% accurate.