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To Catch an Arsonist: Will We Ever Have a Reliable Way to Identify Fire Starters?

Gradual advancements in the art and science of fire investigation continue.
The Skyline Parkway Motel in Afton, Virginia, after arson on July 9, 2004. (Photo: Ben Schumin/Wikimedia Commons)

The Skyline Parkway Motel in Afton, Virginia, after arson on July 9, 2004. (Photo: Ben Schumin/Wikimedia Commons)

A series of fires swept across San Diego County last week, burning down tens of thousands of acres of land and everything on it. Severe drought, high heat, and winds surely contributed to the speed with which the fires spread through the "tinder box" that is Southern California. But how did the fires start? As in all such cases, authorities are considering arson as a possibility. As firefighters fight to contain the blazes, investigators are struggling to keep up with leads on potential criminal suspects. Three people have already been arrested for three different fires, though authorities don’t have direct evidence to charge all of them.

As it happens, arson investigation is a strange and very young science. Researchers are developing and testing new forensic methods all the time; techniques will only improve. These small advances won’t help the countless people in the U.S. who have been sentenced to life in prison for crimes of arson they did not commit and who won’t have their cases re-opened in time for them to be set free. But arson science will still advance, at the same slow and methodical pace that every branch of science does.

Sue Russell previously wrote for Pacific Standard about the primitive, almost voodoo-like methods used in “the dark ages of fire investigation.” She spoke to attorneys at several Innocence Project groups who, along with scientists at several criminal forensics schools, were working to fight wrongful convictions for arson. Some of the cases involved people who had been in prison for three or four decades already. Fighting arson convictions is an uphill battle. “DNA is the undisputed gold standard for exonerations, a virtually unassailable magic bullet,” Russell wrote. “But arson convictions are a new frontier for exoneration work.”

Arson investigation is a strange and very young science. Researchers are developing and testing new forensic methods all the time; techniques will only improve.

Russell explained that there are no formal licensing or training requirements for fire investigators—investigators whose testimony in court may be the sole factor leading to a defendant’s prosecution in arson cases. She cataloged the patterns and clues that were once widely accepted as indicators of arson that are now considered bogus. “Crazed glass,” for example, was the term for a web of lines formed by fire on windows that used to be cited as arson evidence; it is now understood to be an effect of the quick-changing temperature when a hot window is hit by cold water from a fire hose. Discolored “pour patterns” on the floors and walls of a fire scene—supposedly formed by liquid accelerants—is another example.

“Pour patterns” were frequently cited in the now-infamous case of Cameron Todd Willingham, who was convicted of setting a fire that killed his three young children in his Texas home in 1991. Despite mounting evidence Willingham had been wrongly accused and that the fire was an accident, he was executed in 2004. A Texas judge, Charlie Baird, told The Huffington Post’s Michael McLaughlin in 2012 that he had personally tried to posthumously exonerate him, but that the order had been buried. “You can’t do anything for Willingham except clear his name,” Baird said.

Willingham’s case likely benefited (again, posthumously) from media attention; consider David Grann’s stunning profile in The New Yorker and a feature-length documentary. But similar stories like his come up all the time. Baird said that he was moved to make his exoneration order public when he heard the story of another man posthumously found to be innocent, Carlos DeLuna, who was executed in 1989. Then there are the stories that (eventually) have happier endings, too. Last year, with the help of the Exoneration Project at the University of Chicago Law School, James Kluppelberg was set free after spending 25 years in prison for a fire he didn’t have anything to do with. Louis Cuen Taylor spent almost 40 years behind bars for a fire in Tucson that he didn’t set; he was also released last year.

A lot has changed since the days of “crazed glass” and “blistered wood,” and other so-called fire forensic markers, now since debunked. A review study presented at an Interpol Forensic Science Symposium in 2007 summarized the latest scientific research of all the different types of forensic techniques for investigating fires. The review ranged from the very dry and scientific-sounding processes of chromatographic analysis and chemical fingerprinting, to more abstract arts like the psychological profiling of fire-setters and the use of accelerant-detecting canines. Investigators now have precise tools to test the materials found at the scene of the fire, and also to detect the presence of gasoline or other accelerants on the hands of potential suspects.

A new article just published in the journal Forensic Science Internationalexplains the advantages of a computer program that can quickly detect and classify the chemical compounds of burned materials. With a new mathematical model, University of Alberta chemistry professor James Harynuk and his colleagues can run through the chemical data in seconds to determine the presence of gasoline, kerosene, or paint thinner, for instance. It wouldn’t be useful in solving the mystery of massive brush fires, but this is just the type of tool that could have saved Cameron Todd Willingham and others like him.

The article also notes that this new technology will serve to speed up the fire investigation process, but that it’s not meant to replace human analysis—only to complement it. Perhaps arson forensics remains just as much an art as it is a science.