Arson can be one of the toughest crimes to prove, but in Phoenix one arson squad seemed to find answers few others could. Arguably the best arson investigators in the nation with the Numbers to back... See More
Arson can be one of the toughest crimes to prove, but in Phoenix one arson squad seemed to find answers few others could. Arguably the best arson investigators in the nation with the Numbers to back it up. But now they are under fire with some asking whether the investigators have been accusing the innocent. Here is ABC's Byron Pitts with burned, arson squad under fire. Once the investigator gets there we take over. This is captain Sam Richardson. Two fires today already. Captain Fred anders. They're investigators with the Phoenix fire department elite arson squad taking on one of the deadliest crimes in America, and one of the hardest to prove. Definitely not engine fire. We can go into a structure and be able to find exactly where it starts. To a lay person they're just looking at us how do you know that. Reporter: They were the best of the best and had the Numbers to prove it. They solved more cases than any arson unit in the country. This unit right here made ten arrests in the last two or three weeks. We have done it time and time again. Did the success come at the expense of innocent victims. I was being framed for a crime I didn't commit. Going to prison for the rest of my life. Tonight, two people who say they were falsely accused of arson, alleging incompetence, misconduct and worse by a department they claim has run amok. You were in jail for 16 months. It ruined my life. I am still paying for it until this very day. And investigator who says there may be more. I think there is other cases, that there is other innocent victims out there. 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 andies was proud to admit he had a secret weapon. Sandy. Sandy is an accelerant detection canine, a food reward dog, who only gets fed when she works. Her highly trained nose can detect accelerants commonly used in arsons. But there was another force at work. The unit's controversial new director, jack Balentine, a police detective but no prior background in fire investigations. I spent my whole career undercover. Seemed like a great challenge. Balentine was as comfortable posing as a hit man or drug dealer as he was in the media spotlight. His first move as director, launching an intensive training program to transform fire fight nears criminal investigators with the purr lower to arrest. And he admitted the learning curve was steep. We were pretty comfortable on a firetruck. Pretty comfortable to fight a fire. Then we are asked to investigate the fire. We really didn't have a clue. All they have got to do is just get probable cause. My job is to make sure that day can realize success on every one of the cases that they go on. Between Balentine's leadership, the clearance rate skyrocketed, solving just 22% of cases in 2007. 65% in 2010. The highest in the country. But the shining record was about to be called into question. 911, where is your emergency? There is a fire. Hold on I will put you through to the fire department. May 13, 2009, the home of Barbara Sloan was ablaze. Richardson, andies, and Sadie were called to investigate. Okay, this is a video of the back of the house you. Can see we had a pretty good fire here. Reporter: In this video filmed by Richardson. Telltale signs of arson all over the house. The gas was unscrewed from the dryer. The cabinets in every room are open, to allow the air to get into it. Forensic accounting proved that Sloan had $100,000 in credit card debt and had been trying to set house. This house has been on the market, approximate market, approximately for four years for sale. In the corner, huh. Reporter: But the crucial evidence came from Sadie. Detected accelerants at multiple locations around the house. Making the case a slam dunk. Barbara Sloan says she didn't diet. Are you an arsonist? No, I was being framed. Sloan was charged with arson and faced 29 years in prison. I sat down with my family before the criminal trial was to begin, and prepared my son and daughter that their mom was going to jail for the rest of their life. For her defense, Sloan enlisted pat andler, a fire investigator with more than 30 years of experience whchlt in Y --. When you looked at the evidence what was your thought? In the garage. In the garage. The garage is completely engulfed. The first witness says they don't see fire anywhere else in the house but in the garage. Reporter: Not the laundry room with unplugged gas line. Not the kitchen where the iron was face down. A point Richardson would later concede in a deposition with Sloan's lawyers. There was not even an ioata of evidence of a gas explosion anywhere in that home, right? No. Off awe in fact there was no fire damage in the laundry room, isn't that right? No. Reporter: All of the physical evidence pointed to one of Sloan's cars, a Toyota corolla model that had been recalled for defects including cracks he believes sparked an electrical fire that spread throughout the house. Did you ever open the hood of either car to examine the engine compartment of either car? No. Sam Richardson never even entered the garage. So you think this was fire investigation 101? This is below fire investigation 101. This is -- Reporter: But the Sloan case isn't the only one? Just six days prior, Richardson and andies had been called to another house fire across town. There is three separate points of origin here on the back patio. 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 and renter of the house. He was behind on his rent and had been fighting with his roommate. He wasn't paying rent. He came back. They wouldn't let him in. He got mad. And saw him just prior to the fire. Part of the suspicion was that you were freeing to kill your roommate? Correct. Reporter: Any truth at all to that? None at all. Reporter: Richardson using his new training took on the role of interrogator. I know you lit the fire. Let me tell you why. Okay. I got a good video of you coming back. A good eyewitness that saw you back there just prior to the fire. Reporter: Telling you evidence that he did it. He didn't. It was a scare tactic to see if I would admit to some form of guilt. Reporter: Did you? No. Off awe come on, you are a man. Reporter: There was no videotape. Though lying is a time honored police detective tactic to illicit confessions. Some one poured gasoline all over the stuff. The dog is hitting everywhere. Reporter: That much was true. Sadie did alert to accelerants at the scene enough to arrest him and keep him in Phoenix lockup for 16 months. But the case began to unravel. Pat andler who worked on the defense said the fire started because of an electrical short in the attic. Sam Richardson got it wrong. It is embarrassing to not that he is a fellow fire fighter like myself. Reporter: Before the trial, he was offered a plea for one year probation. He refused. Were you not tempted. Probation sound better than 20 years in prison. I don't care if they gave me one second of probation. I would not sign no paperwork to admit guilt to a charge. Reporter: Then the case against Capels fell apart. Traces of accelerant that Sadie alerted to, the results came back from the lab negative. No traces of accelerants, prosecutors dropped the charges. Back on the Sloan case turns out the same thing happened. Sadie found accelerants that the lab did not. Why didn't Sadie get it wrong both times? Could this be why? Fake it for me, okay. Fake it. I could not believe what I was hearing. Reporter: Coming up, more word you might find surprising coming from captain andies. We used to think we had to
This transcript has been automatically generated and may not be 100% accurate.