After the wildfire had burned through nearly 42 acres of grass and scrub trees in an Old Orchard Beach marsh on a blustery April afternoon, Maine Forest Rangers got to work examining the charred trees and scorched soil for a trace of what caused the wall of flames to sweep across the dry, open marsh.

Within weeks, to the shock of first responders in Maine and New England, Old Orchard Beach Fire Chief Ricky Plummer sat before a judge in handcuffs, charged with setting the fire that afternoon – a rare case of a ranking fire official facing an arson charge. Plummer, who has resigned from the fire chief position, told authorities that he discarded a cigarette he’d been smoking in secret and that the fire was an accident, but officials said they found no cigarette butt or smoking materials. It was as if they had searched every stalk in the proverbial haystack, but found no needle.

Can fire investigators, searching a burned area larger than three dozen football fields, really expect to find something no bigger than a paper clip?

The answer, according to fire experts, is absolutely.

Although the techniques of fire investigation have advanced more slowly than the investigative techniques of other crimes, fire investigators today are leaving behind assumed wisdom in favor of scientific rigor, documentation and replicable methodology.

Maine Forest Ranger Mark Rousseau, 50, compares what fuels were burned and what areas were protected from flames to determine the direction of a fire while investigating a recent wildfire in New Vineyard.

Forest Ranger Mark Rousseau compares what fuels were burned and what areas were protected from flames to determine the direction of a fire.

As investigators who examine homicides or rapes use DNA testing to build a case on infinitesimally small specks of blood or bodily fluids, fire investigators now can reliably find significance in the smallest of particles.

In the case of the Old Orchard Beach fire, a detailed search of the area where they believe the flames began yielded no evidence to back up Plummer’s story that he used two paper matches to light a cigarette that he later discarded, sparking the fire in dry, chest-high marsh grass by accident.

“I know better to even be out there with a cigarette,” Plummer told investigators, according to court records.

Yet fire investigators found no cigarette butt, no matches, no evidence of smoking materials.

“During my career I have investigated several cigarette-caused fires and the cigarette has always been present at the origin upon my examination,” Maine Forest Ranger Matthew Bennett wrote in the affidavit supporting Plummer’s arrest. “I searched the area carefully and would have certainly located evidence of this nature if it existed.”

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Maine Forest Ranger Mark Rousseau began his career investigating fires at a pivotal time in the industry. Based in Farmington, Rousseau joined the ranger service in 1999 and was trained in fire investigation in 2003, around the time that modern, science-based practices became the nationwide standard.

Forest Ranger Mark Rousseau says he often talks aloud while investigating fire scenes, like this one in New Vineyard last week. "It helps me work it out," says the Farmington-based ranger, who was trained in fire investigation in 2003.

Rousseau says he often talks aloud while investigating fire scenes, like this one in New Vineyard last week. “It helps me work it out,” says the Farmington-based ranger, who was trained in fire investigation in 2003.

Rousseau was among the investigators who helped examine the Old Orchard Beach fire scene. Although he declined to speak about the findings in that case, Rousseau talked about how he approaches wildfire scenes and what methods and indicators he relies on to draw conclusions about how they started.

For nearly two hours at the scene of a recent wildfire investigation near New Vineyard, Rousseau showed a reporter the usual steps he takes to understand a wildfire’s behavior, tracing its path and ultimately finding a point of ignition and a cause.

The May 11 fire in Starks off Route 43 burned about 2 acres on a gentle hillside near a recently cleared pasture area, charring trees and leaving the forest floor bare and black.

Rousseau, who is also the fire chief in Phillips, was at the fire that day, which gave him an advantage in watching how it moved through the trees and brush.

Every fire investigation takes place in two steps: Find the area of origin, and then examine that area in minute, painstaking detail, looking for evidence of a cause.

A fire could burn 10, 100 or 10,000 acres, but the area investigators focus on is usually much smaller, because it’s where the most important evidence will typically be found.

“Anything that’s outside the area of origin doesn’t matter, because if the fire didn’t start there, it doesn’t matter what ignition sources are there,” said Rich Meier, an independent fire investigator and expert with Chicago-based John A. Kennedy & Associates, the world’s oldest fire investigation company.

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Determining the origin is like drawing circles of a bull’s-eye.

Rousseau said he usually circles a fire scene at least a couple of times, sizing up the shape of the scorched area, looking for what burned and what didn’t: Was it a long, skinny fire, driven by high winds? Did the flames meander aimlessly, or did the fire whip and whirl with the weather?

Rousseau looks at the topography, too. Fire takes the path of least resistance, and tends to burn up a slope much faster than it burns downward.

The intensity and direction of a fire will "freeze" soft foliage such as pine needles in the direction the fire was moving, another indicator of how a wildfire moved and where it began.

The intensity and direction of a fire will “freeze” soft foliage such as pine needles in the direction the fire was moving, another indicator of how a wildfire moved and where it began.

Because every fire tends to start small, there is usually less damage at its point of origin than elsewhere. That means that vital evidence, such as spent matches, pieces of a bottle or a cigarette butt can still be preserved, despite widespread devastation across the rest of the fire scene.

“You’re out there on your hands and knees, and you’re going slow,” Rousseau said. “You might be looking for something as small as the staining on a pebble.”

During his walk, Rousseau takes a knee near a blackened area, gently nudges some oak leaves, and points, his eyes wide. It is a pine cone.

“I love pine cones,” he said. “Not just pine cones, any soft-wood cones. They show those very clear signs of degrees of damage or protection.”

Like people, fire develops a personality, he said, and it is those traits that help him determine a cause. The most difficult fires to investigate are those that never fully develop a character that betrays their origin, he said.

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Fires that rip through grasslands leave their own special indicators, he said. Because fire enters an area low and exits high, many times a single blade of grass will burn at its base and topple over, leaving the upper portion unburnt. On a perfectly flat surface in an area with no wind, a grass fire should spread in a perfect circle, with the grass stems falling to the ground pointing in the direction of the source, like little arrows pointing the way.

The angle of char on tree bark is a reliable indicator of a fire's direction and behavior, offering a road map of how it burned for Maine Forest Ranger Mark Rosseau as he went through the process at this recent wildfire site in New Vineyard.

The angle of the char on tree bark is a reliable indicator of a fire’s direction and behavior, offering a road map of how it burned for Maine Forest Ranger Mark Rosseau as he went through the process at this wildfire site in New Vineyard.

As he works, Rousseau talks to himself, gesturing at shrubs and sticks, tilting his head and moving his hands in the air. As much as the pursuit of a fire’s cause and origin now relies on science, the practice is also informed by years of experience and a healthy suspicion of every piece of evidence.

As he ping-pongs from one side of the fire scene to the other, Rousseau searches for corroboration, recalibrating his ideas and returning to the evidence again and again. When investigators work together on a scene they try to never reveal what they think, or risk tainting another investigator’s judgment.

“No one indicator can be relied upon,” he said. “You have to look at the totality of the indicators.”

Investigating fires, although scientific, still often relies largely on circumstantial evidence, Rousseau said. Unless there is a witness who sees someone strike a match or toss the cigarette butt – or if there’s video that shows the same – fire investigations often hinge on the staining on a pebble, a preserved cigarette filter, or a particle of carbon.

“What we see out here, we have to take this into a court of law and present it to a judge and a jury, who know nothing about the science we undertake to do this,” he said. “We have to take this and put it in a clear enough package to explain it in court.”


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