For Wildfire Investigations, ‘It Really Is a Needle in a Haystack’

She knows it might sound silly, but veteran fire investigator Laura Billon has learned the value of using a childhood teaching tool to explain the art of finding the origin of a fire.

While teaching at San Diego’s Miramar College, she tells students to imagine being shown a picture of a truck, a boat, an airplane and an apple. Which one is not like the other?

“In forensics, you’re looking for the anomaly, something (that) doesn’t belong,” Billon said. Maybe it’s a pile of twigs or a piece of metal or a lighter — an old-fashioned clue in an investigative field that still relies heavily on shoe leather rather than fancy CSI-style gizmos.

Fire investigators this week will be busy knocking on doors and poking around acres of burnt brush as they try to determine the origins of the county’s rampant wildfires. While the high number of fires is suspicious, officials haven’t settled on arson as the cause.

I asked Billon — director of education for the International Association of Forensic Professionals and an instructor with the U.S. Department of Homeland Security — about the unique nature of wildfires and the challenges of uncovering their causes.

How predictable are wildfires compared with fires in buildings?

When you have a fire in a room or a house, when you have something that has a top and four sides around it, it is definitely much easier to predict how a fire will burn or where it’s going to go in terms of having a fuel load.

In a wildland fire, you don’t deal with any of that.

In terms of oxygen, there’s no ceiling or walls encompassing the fire. A fire will continue as long as there another twig, another tree, another leaf — we typically estimate that there’s a ton of fuel per acre — and as long as there’s more air available.

As for the weather, you can guesstimate and listen to the weather reports, but wind direction can change on a dime.

What are the options to put out a wildfire?

You’re looking to remove the fuel through cutting or scraping by hand crew, bulldozers and backfires. You can also put water on the fire or throw dirt at it. If dirt gets thrown at the base of the flames, it will cool the fuel and limit the oxygen, essentially smothering it.

Where do you begin when you’re investigating the cause of a fire?

You start the wildfire investigation the same way you’d do it for any fire: You go from the least burned area to the most burned area.

We want to see how the fire traveled. We’re looking at blades of grass, sides of trees, starting at the ends and working our way in.

What are the most crucial elements of a fire investigation?

We use the 80-20 rule: 20 percent of your evidence is forensic, and the other 80 percent is gathered from interviews.

We’re going to be interviewing as many people as possible. When did you notice the fire? Who reported it and when?

In the case of a wildfire, it really is a needle in a haystack. It doesn’t mean it’s not possible to find the cause. It just creates a very different challenge.