Wildfire's behavior key to finding its source

By Peggy Mihelich
CNN

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(CNN) -- Wildfires, like people, have personalities. And by understanding their behavior wildfire investigators can trace a fire back to its source and find out what and who started it.

"You can learn some really interesting things by looking where a fire's burned...a fire burns faster uphill. And it moves faster when the wind is driving it," says Janice Coen, a wildland fire researcher at the National Center for Atmospheric Research (NCAR).

Coen looks at the weather conditions, scorch patterns on grass, ash deposits and tree damage.

"If you look at a pine tree that's been burned, the needles get frozen in place when the fire burns over it -- they kind of point down wind. That tells you which way the wind was blowing, and directing the flames," said Coen.

These fire direction indicators along with eyewitness accounts from trained first responders help investigators like former senior special agent for the U.S. Forestry Service Paul Steensland, locate the point of origin -- where the fire started and what started it.

A investigation using these techniques led authorities to a suspected serial arsonist they say set a wildfire that killed five firefighters in California in October. (Full story)

Steensland says it's like following footprints through the snow.

"What we are trying to do is retrace the fire's progression away from where an ignition source came in contact with the materials that first ignited it."

And unlike a structural fire, a wildfire first starts very small and low in intensity, building up as it moves away from the point of origin.

"We typically move from the area of most damage to the area of least damage."

That area is usually a quarter-acre to a half-acre in size. When located, the area is tagged off with caution tape and a team of investigators gets to work.

An agent will identify the advancing area or fire progression zones -- where the fire is moving away from the origin -- at its greatest intensity and greatest speed. That's usually the direction that the wind is blowing or the direction of the uphill slope.

Agents will enter a burn area and start a very methodical zig-zag fashion search -- looking for fire transition zones and marking them with colored flags -- red: advancing, yellow: lateral and blue: backing.

Steensland says fires tend to burn out in a rough V or U shape away from the origin area.These yellow lateral areas of transition get closer and closer together as you reach the apex of the V -- the origin area, where the fire actually started. It's usually an area about the size of a table top 5 feet by 5 feet or 10 feet by 10 feet or less.

If an obvious ignition source is not visible, they get down on their hands and knees and look very meticulously for say a match, carbon particle or a catalytic converter particle -- often used to start wildfires, says Steensland.

"We look first with the naked eye. Then we'll look with a magnifying glass or a very powerful reading type glass. If nothing is visible on the surface, then we'll try and brush off or blow away ash and burned debris to expose the layer underneath. And if we still don't find anything, we'll run a magnet or metal detector over it."

It may seem like finding a needle in a haystack but it almost always pays off.

"I've found the head of match on one case, matches on others, cigarette butts. I found a very small piece of metal from a grinder that I recovered with a magnet."

And how easy is it to start a wildfire? Too easy, Steensland says.

"Just a match to the grass and you've got a fire."

But connecting that match to a person -- that's the hard part, requiring good old -fashioned detective work, interviewing witnesses, first responders, appealing to the public for information and doing behavioral evidence analysis such as profiling.

"Most of the cases that we are dealing with are repetitive -- serial arson. The fire setter does not set one fire but has set numerous fires," Steensland says.

The average arsonist sets about 35 fires before being apprehended, according to Steensland.

"And we usually catch the guys. If they continue to set fires, we will eventually catch them -- it's just a matter of when not if."

Last week Raymond Lee Oyler, 36, from Beaumont, California, was charged with starting a deadly blaze in southern California. (Watch Oyler's court appearance -- 2:04)

Firefighters Mark Loutzenhiser, 44; Jess McLean, 27; Jason McKay, 27; Daniel Hoover-Najera, 20, Pablo Cerda, 23, died fighting southern California's Esperanza fire. (Watch the memorial service -- 1:04)

The 40,200-acre blaze destroyed 34 homes and 20 outbuildings.

Olyer was charged with five counts of first-degree murder, 11 counts of arson and 10 counts of use of an incendiary device. Charges also include seven fires set over the past year.

Olyer pleaded not guilty.

Meanwhile, firefighters are battling a wind-fueled wildfire about 60 miles east of Los Angeles that began on Monday. The fire threatens as many as 100 homes and caused two school evacuations. (Full story)

Investigators are working to determine the cause of that blaze. (Watch the blaze at it gets closer and closer to homes -- 1:00)

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