DENVER (AP) -- Thousands of southern Californians helplessly watch their homes and hillsides devoured by flames and ask, "Who could do this?"
The answer: Mostly careless hunters, campers, smokers, trashburners. But also angry, bored kids. Drunks. Ghostly psychopaths who vanish into the smoke. Too often -- and most disturbingly -- firefighters themselves.
If history is any guide, it may take years to arrest those believed largely responsible for a week of fire that has killed at least 20 people and destroyed 2,300 homes in what could be California's most expensive catastrophe. And they may never be caught. The typical rate of solving wildfire arsons is less than 10 percent a year.
Authorities in California are circulating a composite sketch of a young, long-haired, white man driving a light-colored van. He is suspected of igniting at least one, if not more, of the 13 blazes that have burned in a hellish corridor extending from the mountains north of Los Angeles to San Diego and across the Mexican border.
Wildfire arson is a surprisingly common crime despite harsh penalties. In California, it can carry a sentence of 10 years-to-life, plus murder charges when innocents die.
But it's one of the most difficult crimes to solve. That's because investigators are confronted with an incomplete puzzle of fragile clues like ashes, matchheads and tire tracks, which can be obliterated in a single thunderstorm.
Witnesses are uncommon and their recollections hazy. In the West, where overgrown forests extend for 100 miles and mountains soar into the horizon, it's too easy to melt into the rugged background.
"The arsonist could drive to an adjacent ridge to watch his handiwork and you would never know," said Paul Steensland, a senior special agent with the U.S. Forest Service. "If they are serial arsonists, we will catch them. But it may take a number of years."
The nation has averaged 103,112 wildfires annually over the past 10 years, according to the National Interagency Fire Center in Boise, Idaho.
There are no firm numbers for wildfire arson incidents, arrests and convictions. Even a clear distinction between accidental fires and malicious ones is difficult to distinguish in the record-keeping. Experts say there just are too many jurisdictions and agencies to coordinate, from the Forest Service to county volunteer brigades, law enforcement and even the military.
But the problem is obvious. Investigators agree that human activities, not lightning, are responsible for 9 out of 10 wildfires. That breakdown remains constant even in drought years like 2000 and 2002.
The easy part, investigators say, is finding the fires' physical origins. Unlike structure fires, which tend to burn hottest where they start, wildfires usually begin cooler.
They rapidly spread, propelled in a V-shape by the wind, terrain and fuel. Investigators quickly work backward, narrowing the path by reading scorch marks on trees and the direction in which intense heat sucks the moisture from unburned leaves and needles, "freezing" them like signposts.
About three-quarters of the human-caused fires result from carelessness, fire investigators say. Hunters and hikers leave smoldering campfires, or grass brushes against the hot muffler of an off-road vehicle. When the ignition point of dry forest litter is only 500 degrees Fahrenheit (260 Celsius), it takes just a few seconds and a puff of wind for a spark to grow into a rising wall of flame.
Investigators look into every reported fire, but how to prosecute the accidents is left up to local officials.
San Diego authorities say one of this week's fires that killed 12 and burned more than 1,000 homes was sparked by a lost deer hunter who set a signal blaze in the Cleveland National Forest. He was cited with a misdemeanor.
But the number of accidental fires still leaves more than 23,000 blazes a year to the firebugs.
Sometimes the cops get lucky, like last year when they literally bumped into Timothy Nicholas Terry of Eugene, Oregon, down the trail from a smoke plume near the McKenzie River. Terry was charged with setting three fires in September 2002. But his vehicle had been reported near previous blazes, and authorities are re-examining scores of fires on both sides of Interstate 5 over the past five years.
Another statistical twist: Arsonists typically get charged only for their last fire -- the one that got them caught. But one arrest can effectively solve hundreds of incidents spanning several years, even if the statistics never reflect it.
"In San Luis Obispo, I arrested one guy who we knew set 600 fires," said Douglas Allen, who chairs the wildfire committee for the International Association of Arson Investigators. Ironically, wildfire forced Allen to evacuate his home near Lake Arrowhead, California, on Wednesday.
"These people continue to set fires until they are caught," Allen said. "But one arrest can make a big difference."
The psychologists' profile of a typical woods arsonist is a person marinating in bottled-up anger and intimidation. Except, that is, for the intoxicating moment when the match strikes and the flame flickers. Then he exults as the sirens wail and people flee, terrified.
Fairfax, Virginia, forensic psychologist Neil S. Hibler says that's when the firebug feels, "I did that. Man, I'm special."
"This is a coward's game," Hibler said.
Some are Beavis-style delinquents, like the seven Halloween pranksters who lit the 2001 Red Bird fire in the Daniel Boone National Forest in Kentucky. It left a firefighter in a wheelchair, paralyzed by a falling black locust tree.
Disgruntled workers and ecoterrorists may seek revenge against logging companies; for example, $50 million in timber in Louisiana was torched in 400 separate blazes in 2000.
Yet others see profit, not destruction, in flames. In the 1990s, investigators probed many blazes around depressed logging towns in the Pacific Northwest, but there were no convictions.
In hard times, arson-as-public-works is tantalizing: The government spends more than $1 million a day supporting fire crews, contracting locally for everything from sandwiches to bulldozers. And when the flames are extinguished, salvage logging of charred timber takes years, generating hundreds of jobs and payrolls topping $40 million.
But for investigators and homeowners alike, the most perverse category of wildfire arsonist are the firefighters themselves.
The most celebrated case was John Orr, an arson sleuth for the Glendale, California, fire department serving a life sentence for setting a 1984 hardware store blaze that killed four people.
He also was convicted of conducting a remarkable arson campaign that damaged 67 homes along with open land. He was arrested after penning a novel, "Points of Origin," depicting a firefighter who torched a hardware store and other businesses for sexual pleasure.
In 2002, firefighters were responsible for two of the nation's largest wildfires.
In Arizona, Leonard Gregg, a contract firefighter, was sent to a prison hospital for a psychiatric evaluation after being charged with setting the Rodeo fire in the state's rugged eastern mountains. At its worst, the inferno spread 50 miles wide; one local fire chief described it as "walking down the aisles of hell." Containing it cost public agencies $43 million.
Prosecutors said Gregg confessed to setting fire to dry grass in hopes of earning $8 an hour to extinguish the flames for the Bureau of Indian Affairs.
In Colorado, former Forest Service seasonal worker Terry Barton pleaded guilty to starting the Hayman Fire, which consumed 137,000 acres southwest of Denver and destroyed 133 homes.
She claimed to be distraught over her crumbling marriage and said she burned letters from her estranged husband in a campground fire ring. Investigators still don't buy her story.
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"I never found paper ash," Steensland said. "I did find three matches stuck head-first into the ground, spaced a half-inch apart."