How Arson Investigation Has Changed

Posted by PBS Independent Lens on

Theo Love’s film Little Hope Was Arson explores a linked series of suspicious fires set in East Texas in 2010. In the “buckle of the Bible Belt,” ten churches burned to the ground in just over a month, igniting the largest criminal investigation in East Texas history. The film premieres on PBS this coming Monday, April 6 at 9 pm CT (check local listings), and of it, The New York Times wrote that the film shows “Americana unvarnished and, because of that, as absorbing as it is respectful.” [Learn more about the film >>.]

Because of the nature and size of the serial arson case in East Texas, the investigation involved 15 agencies who deployed at least 100 investigators to relatively quickly hone in on the suspects. As you’ll see in the film’s depiction of the forensics of arson investigation, it is a crucial but inexact science that’s been evolving and improving in recent years.

We’ve compiled some of the more interesting writing about how arson research and criminal investigation has evolved, and still needs to evolve further. If you really want to be a fire investigation history nerd, you can read this lengthy but interesting paper, The Evolution of Fire Investigation, 1977-2011. Just as with other criminal investigation techniques, the methods are catching up with the science:

Up until recently, process of elimination – or negative corpus – passed as a reasonable way to prove an arson case. It was removed from the National Fire Protection Association’s fire investigation manual in 2011.

“In the past it was an accepted practice,” says Bob Duval, a senior fire investigator at the NFPA, the Massachusetts based trade organization that publishes the nation’s most widely accepted guide for investigating fires.

“If you didn’t have any viable source of ignition then it had to be arson.”

Negative corpus, some argued, was part of the scientific method – a science-approved way of ruling arson without any specific evidence.

Similarly, when investigators couldn’t find an ignition source, some came to rely on evidence that indicated that a fire had burned especially hot or fast. Hot, fast or low burning fire indicators became telltale sign of arson, Duval says.

A story on NPR, “Arson Forensics Sets Old Fire Myths Ablaze,” explores how a lot of what we thought we knew about arson was, frankly, wrong.

[Fire investigator John Lentini] says that in the early days of arson forensics, the only science that happened was chemists looking for signs of gasoline on a piece of rug in the lab. In the field, investigators relied on anecdotal experience.

“If somebody would see an artifact and then find gasoline, they would make a connection,” Lentini tells Weekends on All Things Considered guest host Laura Sullivan. “And the next time they would see that artifact, they would just assume that gasoline must have caused [the fire].”

The problem was that anecdotal experience could lead an investigator to the wrong conclusion. In recent years, fire researchers and the changes to fire investigations have shattered dozens of arson myths as the science behind arson forensics continues to evolve.

Faulty Investigations

There are people still in prison who may have been wrongly convicted of arson, due to faulty investigation methods in that time. The most widely-reported recent example of this, to a very troubling degree, is that of Cameron Todd Willingham, who was executed in Texas despite mounting evidence in his defense. An excellent piece about the case was published in The New Yorker by David Grann. It’s a truly fascinating study on how tricky and spotty arson forensics have been.

Writing in Discover magazine, Douglas Starr looks at the history of modern fire research and then investigates fire researchers who are shattering arson myths, even though courts are continuing to convict people using faulty evidence.

The modern study of fire in America was born in the 1970s, when funding was plentiful and consumer protection politically popular. According to a 1973 Nixon administration report called America Burning, fires in the United States caused more than $11 billion in annual damage and took an estimated 12,000 lives. The numbers were later found to be exaggerated, but the report galvanized Congress to support the young field of fire research. As part of that support, Congress created a Center for Fire Research at the National Bureau of Standards (NBS), which has since become the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland. “Until then, there really was no fire safety science,” says Vytenis Babrauskas, who in 1976 became the first American to receive a Ph.D. in fire science, from the University of California, Berkeley. With the budget to hire more than 100 bright young engineers, including Babrauskas, NBS began with a fundamental question: How do you quantitatively measure a fire?

Working at NBS in the early 1980s, Babrauskas invented a device that accomplished that purpose. The cone calorimeter [which is not small; check out accompanying picture – ed.]

Cone calormeter

resembled a vent hood with a series of ducts attached to the top of a small sealed chamber. When an object, such as a piece of plastic or wood, was burned in the chamber, the device measured a range of variables. It registered the chemical composition of the fumes, the accumulated energy released, and the rate of that release; the temperature, pressure, and opacity of escaping gases; the opacity of the smoke; even the weight of soot compared with the weight of the original substance. It measured so many characteristics that it became known as the Swiss Army Knife of fire research. The first calorimeter could handle small objects a few inches on each side. Later, Babrauskas designed a model big enough to test burning furniture, aptly called the Furniture Calorimeter. “It was basically a big hood with all sorts of instrumentation to capture and measure the gases,” he says.

Starr goes on:

Since then, other high-profile disasters attracted extensively trained scientists with their expensive technology, but the average fire did not. The typical local arson investigator, assigned from the police force or the fire department, had never taken college-level chemistry or physics. He learned on the job, by watching other arson investigators, many of whom had learned the trade from their superiors. The misguided notions that older arson investigators subscribed to seemed commonsensical, if you didn’t insist on seeing lab work to support them.

The ATF, who figure prominently in the Little Hope case, have stepped up their game, too, when it comes to arson research, including a new tool that’s even less portable than the calorimeter. From that NPR story:

Some of the newest research on how fires start and burn is now coming from the Bureau of Alcohol, Tobacco, Firearms and Explosives. The federal agency has always done a little fire research, but in 2003 it went all in with a new lab in Beltsville, Md., built just to burn things up.

On a recent visit, researchers were setting a diesel oil fire in their Fire Research Laboratory. The lab’s chief, John Allen, says theirs is the largest forensic investigative tool in the world.

The room is massive and open, akin to an airplane hangar. Overhead, a 40-foot by 40-foot exhaust unit, similar to the one over your stove, sucks out the smoke and heat from the fires set in the lab to measure carbon dioxide and carbon monoxide, among other things.

The large exhaust hood in the ceiling of the ATF’s Fire Research Lab in Beltsville, Maryland is used to suck up smoke and heat from the fires set in the lab to measure carbon dioxide and carbon monoxide, among other things.

The lab also houses a quarter-scale model of a living room complete with a couch, TV, chairs and a baby crib and toys. Allen says they use this to test fires, take measurements and time flashovers – how long it takes for flames to go from “a fire in a room to a room on fire.”

In the field of arson forensics, things can get rather specific. There’s even debate over which kind of container (glass mason jar, paint can, or nylon evidence bag) works best when it comes to capturing fire scene debris.

But as research progresses, we can only hope and assume that arson investigation will become more of a, well, exact science.

Meanwhile, here’s how Los Angeles firefighters were trained to investigate arson in the 1950s:

You likely won’t make it through the whole thing, but it’s an interesting glimpse into the past, even if they make the “arson department” seem a little film noir-ish.

Of course, then there’s the problem of budgets, too. A lot of fire departments are not funded as strongly as they need these days, but some gamely fight on. The short film below will air after Little Hope Was Arson on PBS (and would make a good double-feature with Detropia as well.)  And you can read more about it here: “A City in Flames: Inside Detroit’s War on Arson.”

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