(CNN) -- This is the story of two fathers who drank too much and fought with their wives but, their families say, loved their children more than anything in the world.
The two never knew each other. One was in Texas and one in Pennsylvania, but each watched a fire swallow their home with their children inside.
One father, Cameron Todd Willingham of Corsicana, Texas, was convicted on murder charges; authorities said he set the fire that killed his three children in 1991. He was executed by lethal injection in 2004.
Across the country, at a prison outside of Waynesburg, Pennsylvania, where authorities say they hold the "worst of the worst," is 50-year-old Daniel Dougherty. He, too, was found guilty of deliberately igniting fires in his home that killed his two sons, Danny, 4, and Johnny, 3, in 1985. Police arrested Dougherty 14 years later, when his estranged wife came forward and claimed he confessed. A jury found him guilty on capital murder charges in 2000.
He is awaiting death.
Last month, a Texas state board admitted in a preliminary report that flawed arson science was used in Willingham's investigation.
The board's announcement raises a frightening question: Could the state of Texas have executed an innocent man?
Like Willingham, Dougherty has maintained his innocence from the start. He is trying to prove he isn't responsible for the flames that engulfed his house and that he is also the victim of flawed arson science.
"We have an innocent man on death row who has been languishing there, and there is absolutely no evidence that a crime occurred," said his attorney, David Fryman. "We've been trying our best to right that wrong."
Dougherty and his attorneys at Ballard Spahr in Philadelphia, Pennsylvania, are waiting on the Pennsylvania Supreme Court to decide whether to hear his petition for post-conviction relief filed in 2006. A crucial element of the appeal is the reports of two arson investigators who have re-examined the evidence and found no conclusive indicators of arson.
With science on his side, Dougherty hopes the court will set him free -- before it's too late. No execution date has been set.
Dougherty's version of the blaze doesn't paint him as a murderer but as a failed hero, who tried twice to rescue his sleeping sons with a watering hose and ladder, according to court records. By the time authorities extinguished the fire, his sons had already died from inhaling the toxic fumes.
CNN requested an interview with Dougherty in prison, but his attorneys declined. They did assist CNN in reaching out to Dougherty through letters. Dougherty declined to be interviewed, but wrote back, calling his situation "an injustice that has been done to my loved ones and I." He added that, "Words cannot describe the depths of anguish and frustration I feel."
Is arson science to blame?
John Lentini and Angelo Pisani -- two of the country's renowned arson investigators -- have conducted thousands of fire scene inspections. Five years ago, they received a call from Dougherty's attorneys.
Separately, the investigators combed through the reports, testimony, photographs and other evidence from the original fire scene. Contrary to the fire investigator's original report in 1985, Lentini and Pisani argued there were no signs of arson in Dougherty's home. Such expert testimony was never presented by Dougherty's attorney in his 2000 trial.
In the last two decades, advances in arson science have spurred some investigators and lawyers to question past arson convictions. Some attorneys estimate dozens or even hundreds of cases may have been based on faulty arson science. There are no figures on how many arson cases have been successfully refuted.
Dougherty's original attorney gave a statement in the appeal that he didn't seek assistance from outside fire investigators. He admitted in Dougherty's appeal that his team had "presented little from which to make an argument for life."
The National Fire Protection Association, a fire safety organization, reported there were more than 200,000 intentional fires set to structures in 1980. In 2007, that number dwindled to 55,000. Arson investigators say the steady decline of arson cases can be interpreted different ways: Either there are dramatically fewer cases of intentional fires, or arson science has reduced the number of fires being categorized as intentional. This suggests that some previous cases deemed arson may not have been, they say.
In their report on the Dougherty case, Lentini and Pisani say they believe Philadelphia Assistant Fire Marshal John Quinn, who led the initial probe, relied on outdated arson investigation techniques.
In his 1985 report, Quinn had determined three fires took place on the first floor of Dougherty's brick home: one by the sofa, another by a love seat, and a third under the dining room table.
Quinn concluded only a person could have set the fire in three separate places. Quinn declined CNN's request for an interview.
"There is no evidence to indicate it is arson," said Lentini, who provided an expert report in Dougherty's 2006 appeal and also reviewed the Cameron Todd Willingham case in 2004. "The only evidence he [Quinn] has is his three points of origin and those three points of origin are a figment of his imagination."
Pisani and Lentini argue that the multiple burning spots were likely the result of a "flashover" -- a naturally occurring phenomenon during a fire. In a flashover, the enclosed room can get very hot, reaching temperatures as high as 1,100 degrees Fahrenheit. The room eventually combusts, resulting in various burning points.
Flashover fires can be mistaken for arson because they leave the appearance of multiple points of ignition, they said. Lentini added Pennsylvania is "on their way to executing an innocent man."
Pisani and Lentini also reported the origin of the fire could not be determined because of extensive damage to the room.
The Philadelphia District Attorney's Office rejected Dougherty's claims of innocence. They said a flashover fire requires an enclosed space, but that Dougherty's living room, where the fire occurred, was not an enclosed space since there was a stairwell. They also argued Dougherty managed to emerge from the house without burns or signs of smoke inhalation.
"We are litigating this," said Joseph McGettigan, first assistant district attorney at the Philadelphia District Attorney's Office. "The jury's verdict was a proper one."
The Dougherty trio: 'Danny loves kids'
Daniel Dougherty, son of a Philadelphia police officer, was born in 1960 and grew up in a working-class neighborhood with five siblings.
Known as the "outgoing" middle child, he made friends and girlfriends easily. His father's death from heart problems crushed the 14-year-old Dougherty, who began to drink.
Dougherty never finished the 10th grade. He met his first wife, Kathy Fox, and they had their first son, Danny, in 1980. Two years later, they had their second boy, Johnny.
Danny, 4 years old at the time of the fire, was fearless and curious. He liked riding roller coasters with his father. He constantly peppered family members with questions. Johnny, 3, was quieter.
Dougherty was a functioning alcoholic, his family says. He rarely missed a day of work as a mechanic, his family said. He brought his sons to work so they could spend more time together.
"Danny loves kids, no matter whose kids they are," said his older brother, Norman Dougherty, 57, of Philadelphia. "He loves my kids, his nieces and nephews. He'd take them to the park. He was good like that."
Dougherty's older sister, Karen Dougherty, 53, invited them over for Sunday night dinners at her home. She said her brother relished in his role as a father. He was the first to take his children -- and hers -- sledding each winter.
"Our father passed away when my brother was young so he always had the kids close to him to make sure nothing would happen to them," she said.
On August 24, 1985, the night of the fire, Dougherty was supposed to be at an Alcoholics Anonymous meeting. He skipped the meeting and instead went to a bar, where he got into a verbal argument with his girlfriend at the time (she was not the mother of the two boys). He came home, made himself dinner and fell asleep on the sofa in his living room, according to his testimony at trial. He said he awoke to see the curtains in flames. His children were asleep upstairs.
He ran outside to get the neighbor's garden hose, but the hose was too short. He tried to get water near the window of the house, but he was too late. Flames were already bursting from the house.
The glass exploded, cut his arm and pushed him down.
Next, he grabbed a wooden ladder. But the fire was too powerful. He testified it "blew him down."
"He was so destroyed," said Judy Sorling, 54, who still lives several houses away on Carver Street where the fire took place. She told CNN she saw Dougherty standing with the hose, attempting to put the fire out. "He kept yelling for help."
When firefighters arrived, Dougherty was frantic, screaming at police to save his children. His aggressive and erratic behavior worried police. Authorities shoved his face in the mud and he was taken away, court documents say. Dougherty testified he wanted to die at that moment.
Authorities sifted through the charred remnants of the home and determined the fire had been intentionally set.
Police questioned Dougherty and his family members, but no arrest was made.
Are arson investigations an art or science?
Scenes from popular television shows like CSI often depict detectives relying on forensic science and lab work to draw conclusions. But in the realm of arson investigations, experts say science has played a small role until more recently.
Until 1992, some arson experts say, guidelines for determining arson were largely based on hand-me-down myths practiced by fire investigators with little formal training. In 1992, the National Fire Protection Association released its first arson guidebook based on years of studies and simulations.
The guidelines, known as NFPA 921, were initially met with resistance from fire marshals and officers across the country, who believed arson investigations were an art rather than a science.
"It was gumshoe work, not really analysis and conducting studies," said Gerald Hurst, an arson investigator with a Ph.D. in chemistry, who examined the arson findings in the Cameron Todd Willingham investigation from 1991. He concluded the arson science used in his case was "junk."
In 2006, Hurst independently examined Daniel Dougherty's case. Hurst, too, believed that the multiple burning points were the result of a flashover fire.
The fire that killed three people in the Willingham case in Texas happened in 1991, a year before NFPA 921 was released. In February 2004, Willingham was executed. Later, three reviews of evidence by outside experts concluded the fire should not have been ruled arson. The reports stated a flashover was likely responsible for the fire at Willingham's home.
"There can no longer be any doubt that an innocent person has been executed," said Barry Scheck, co-director of the Innocence Project, which uses DNA evidence in efforts to prove the innocence of people they believe were wrongly convicted. "The question now turns to how we can stop it from happening again."
From prison, a father waits for a second chance
In the years after the fire that killed his two sons, family members said Daniel Dougherty changed. His addiction to alcohol intensified as he tried to cope with his loss. He eventually divorced his wife and remarried, then divorced again.
Dougherty received a surprise visit from police in 1999, about 14 years after the fire. His second wife, Adrienne Sussman, had reported to police that he confessed to using gasoline in the fire. Dougherty was arrested.
Sussman's claim should have been dismissed because no fire reports showed accelerants had been used, Dougherty's attorneys argued. At the time Sussman went to police, she was engaged in a custody battle with Dougherty over their son Stephen, court documents say.
Prosecutors supported their case with the statements of two jail house informants who said Dougherty confessed to them in his cell. But Dougherty's attorneys say the jail house informants are unreliable. They point to studies that show in-custody informant testimony is a leading cause of wrongful conviction in capital cases.
Dougherty's first wife and the mother of the deceased children, Kathy Fox, is now remarried. She said she doesn't believe he intentionally killed their children. She never testified in the original trial because Dougherty's attorney didn't ask her.
"Knowing Daniel and his relationship with his children, I cannot believe he would have burned them to death," she said in statement presented in Dougherty's appeal.
So how do lawyers prove a man's innocence more than two decades after a fire occurred?
The task is almost impossible, said David L. Faigman, a law professor at the University of California, San Francisco. Disproving an arson case is more challenging because the findings aren't as clear-cut as DNA, he said. He said the petitioners have the burden to prove the arson didn't occur and that they weren't involved.
"Courts are already reluctant to open old cases without something like DNA that is really demonstrative proof of someone's innocence," Faigman said.
Cameron Todd Willingham's family in Texas is on a quest to prove he is innocent. While the Texas state board's preliminary findings admitted to flawed science, they also found the investigators did not commit negligence. Still, his family is hoping the board's final findings, expected to be released in October, will exonerate him.
"It will help us with public opinion," said David Fryman, Dougherty's attorney at Ballard Spahr, about the Texas state board's initial announcements. "I think it can serve as a persuasive influence that this is the real issue. It's a scientific issue, and we don't want to have another Willingham."
Dougherty's fate rests in the Pennsylvania Supreme Court, which could take years to make a decision. If the Pennsylvania Supreme Court denies his post- conviction relief, his attorneys say they will have to go to federal court.
Meanwhile, Daniel Dougherty marks his time on death row in Pennsylvania. He's in solitary confinement. At 4 a.m., he is awake and listening to the radio through his headphones. By 5 a.m., he says a prayer and starts his routine of medicines for a number of ailments, including stomach problems. He's worried about whether his body will hold out long enough to prove his innocence.
His food comes through a locked slot on his cell door. He plays dominoes most days. TV helps him get through. On Mondays, Wednesday and Fridays, he exercises.
He occasionally receives letters from his common-law wife, Kathy Halin, and his family. They are too poor to visit him on the opposite end of the state.
Johnny and Danny, his sons who died in the fire, remain a topic of conversation that evokes "severe hurt," he said.
"I LOVED (and still do) my sons more than life itself," he wrote.
He added in his letter that time may heal wounds, but nothing can heal this one.