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Monday, Oct. 29, 2007 | The official causes of most of the wildfires that wrecked much of San Diego County are still “under investigation.”

But with hundreds of thousands of acres of charred landscape to sift through, fire investigators, the detectives of the firefighting world, have their work cut out for them if they are to ever truly understand what triggered the more than a dozen devastating wildfires that have wreaked havoc through San Diego County.

The investigators will have to weave together thousands of pieces of physical evidence with hundreds of interviews and data about the weather and fuel conditions of each fire zone. By analyzing “burn patterns” from the air and from in amongst the blackened landscapes, they will track the fires backwards through time, hoping to center in on the original source of each blaze.

It’s a scientific process, driven in part by intuition but mainly by an intricate understanding of how a fire lives and breathes — something that investigators say can only be developed after years spent in the field and in classroom training sessions. It’s also a process that fire investigators keep guarded from the public, wary that if arsonists or terrorists find out exactly how their crimes will be investigated, they may adapt their methods.

“I’m gonna give you some tricks, and I guarantee I’m not gonna give you all my tricks,” said Doug Lannon, a firefighting veteran and fire investigations instructor for CalFire.

Lannon said all of the 16 fires that burned and are still burning in San Diego County are currently under investigation. But because CalFire only has so many investigators, he said, and Southern California was hit by so many fires in such a short period of time, it could be awhile before any of the causes are known.

Fire investigation is essentially three-pronged: Investigators combine on-scene evidence gathering with data collection and interviews of eyewitnesses.

For a large wildfire, each of those elements is usually tackled by a different investigator or team of investigators, said Steve Mackaig, who runs an independent fire investigation company in El Cajon. At first, it often helps to keep each aspect of the investigation separate, Mackaig said, but eventually the team will come together, attempting to draw the clearest possible picture of how the fire developed.

Key to each investigator’s work is getting to the scene early. Evidence and eyewitnesses memories are freshest just after a fire has begun, Lannon said, meaning time is of the essence.

“I’m going to try and get my investigators there as soon as I can so that we can capture whoever it is that might have information that remains on the scene,” Lannon said.

The first phase in investigating a large wildfire is to establish the general area where the fire started. That’s done by tracking the fire backwards through the areas it has burned and by interviewing residents and firefighters who watched the fire in its early stages.

Physical evidence often points the way.

Investigators can tell by looking at a fencepost or a tree trunk which way the fire was traveling when it reached that spot, Lannon said. If, as in the recent wildfires, the flames have been stoked by strong winds, the fire will have traveled in the direction those winds are blowing. Often the fire’s path forms a “V” pattern that investigators can see from the air and on the ground.

By cross-referencing the physical pointers with eyewitness accounts, an investigation team can establish roughly where the “heel” of the fire began.

“They work in smaller and smaller circles until they get to the source of each fire,” said Rick Hutchinson, deputy incident commander for the Witch Fire, which burned almost 200,000 acres of northeastern San Diego County.

Mackaig said if an investigating team can narrow down the origins of the fire to a 1,000-square-foot area, they can move on to the second phase of the investigation: Sifting through the original fire zone for clues.

Lannon said throughout the investigation process investigators are essentially trying to rule out different causes for the fire. Downed electrical cables, vehicle fires, lightning strikes and even spontaneous combustion are all probable causes for wildfires, he said.

The investigation team will often divide the zone where the fire probably started into a grid of smaller patches to search more closely. Then they will start to meticulously search each square of the grid for incriminating evidence, like the shell of a burned out car or a downed electricity cable.

Sometimes that search leads to some extraordinary findings, like the time Michael Merriken, an investigator with the San Diego Fire Department’s Metro Arson Strike Team, learned about a fire that had been started by a large hawk. The hawk flew into some electricity lines and its wingspan formed a circuit between two lines, causing the bird to go up in flames. Investigators found the charred remains of the bird below the electricity lines, with an area burned out all around it, Merriken said.

More often, investigators will find the remains of a blown-out transformer or a campfire that has gotten out of control, Mackaig said. Sometimes they find machinery that has short-circuited or the remains of fireworks that have landed in dry brush.

Sometimes, however, the investigators don’t find anything.

Though they work on assumption that there is a non-criminal cause to the fire, sometimes investigators can’t find any probable cause for a wildfire. That’s where arson comes in.

If an investigator reaches a conclusion of “negative corpus,” meaning they have eliminated all other possibilities, they will initiate a criminal investigation for arson. That usually involves bringing in law enforcement agencies to interview any witnesses to the early stages of the fire and to continue searching for evidence. That happened in Orange County last week when the FBI was called in to help CalFire catch the person who lit a wildfire that by Sunday had burned almost 29,000 acres and was just 50 percent contained.

Mackaig said investigators usually figure out a definite cause for wildfires, however. The investigation process can take more than a year, he said, but the fire detectives normally figure it out eventually. But because of the sensitive nature of those investigations, Lannon isn’t too keen for the public to know exactly how his investigators figure out which wildfires are arsons and which are naturally caused.

“Do we use forensics? Sure. Could we do a ‘C.S.I. Wildland?’ Absolutely. Do I want to? No,” he said.

Please contact Will Carless directly with your thoughts, ideas, personal stories or tips. Or send a letter to the editor.

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