making the case a slam dunk. >> barbara sloan says she didn't diet. >> are you an arsonist? ramed. >> 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 o

. >> reporter: barbara sloan and a former sheriff's deputy claim they were falsely accused of arson.il for 16 months? >> it ruined my life. >> reporter: the findings of an arson investigator was hired by the defense. >> i think there are other cases, other innocent victims out there. >> reporter: nearly five years ago abc news was given access to this elite unit, an inside look at what made them the best in the nation. >> sadie is an accelerant detection canine. she's a food reward dog. >> reporter: the unit is run by a charismatic and confident former police detective, jack valentine, who by his own admission had no prior background in fire investigations. under his leadership, the unit's clearance rate skyrocketed from solving 22% of the cases in 2007 to 65% in 2010, the highest in the country. back then the team was proud to boast about their success. not now. >> can we talk to you about the investigation? i take it the answer is no. >> reporter: back when they were talking to us, the captain made an interesting statement about their investigative techniques. >> we used to think t

barbara sloan believed she was falsely accused to boost the unit's arrest numbers. >> i believe he wason clearance rate to be the best in the nation. >> the case is under review by the phoenix public safety office. results are due back in the coming weeks. >>> still ahead on "world news," the huge surprise for that seattle college student who may have saved countless lives by bravely taking down a gunman. how perfect strangers are saying thank you to him and his bride to be. she keeps you on your toes. you wouldn't have it any other way. but your erectile dysfunction - it could be a question of blood flow. cialis tadalafil for daily use helps you be ready anytime the moment's right. you can be more confident in your ability to be ready. and the same cialis is the only daily ed tablet approved to treat ed and symptoms of bph, like needing to go frequently or urgently. tell your doctor about all your medical conditions and medicines, and ask if your heart is healthy enough for sex. do not take cialis if you take nitrates for chest pain, as it may cause an unsafe drop in blood pressure. d