Part One of this article discussed wildland fire
fuels, fire spread, and possible causes. Part Two covers the
investigation of wildland fires.
Wildfires should be investigated using a
systematic approach. Below are the suggested key elements of such an
approach. The general approach in interFIRE VR can be adopted
for a wildland fire.
Investigating a wildfire involves unique physical
hazards. The investigator must:
- be aware of areas of the fire that are
- keep Incident Command apprised of his/her
location at all times
- never enter an area without an avenue of escape
- constantly re-assess the safety
conditions based on changes in the fire
- remain alert for smoldering and the
potential for rekindle
- monitor the weather, especially wind
changes, and how it changes the situation
- be careful when disturbing fire debris.
If the underlying material layers are still hot, moving the debris
around can expose the heated material to oxygen, causing it to
- remain alert for falling debris from
damaged trees and hillsides
- always wear proper safety gear, as
defined by NFPA 1977, NFPA 1500 and OSHA
As with a structure fire investigation, protecting
the integrity of the fire scene is the key to preserving evidence.
All scenes should be treated as a potential crime scene until the
cause has been determined to be accidental or natural. Traffic
through potential area(s) of origin should be limited to only
necessary personnel for fire suppression, safety and investigation. A
perimeter should be established and secured by physical barrier
(rope, tape, etc) and law enforcement personnel deployed to enforce
it. However, many wildland fires burn very large areas and it may not
be possible to encircle the perimeter of the entire burn area. In
these cases, the investigator should identify potential area(s) of
origin as soon as possible, then establish a physical, patrolled
perimeter around those areas. All personnel who enter and exit the
area should do so through controlled points, logging in and out.
Observation and Documentation
Many of the same best practices in observation of
a structure fire scene apply to a wildland fire scene. These
- Taking contact information from all
witnesses as soon as possible.
- Recording vehicle tag information for
vehicles in the wildfire area, as well as location and direction of
any moving vehicles.
- Recording physical descriptions and
contact information of anyone in a crowd watching the fire; arsonists
have been known to watch their handiwork. Also record information for
anyone on horseback.
- Examining the area of origin
- for ignitable liquid containers
- for signs of a delay device or
- for signs of potential causes,
such as campfire rings, glassy residue from a lightning strike, or
- for trace evidence, such as
footprints and tire tracks
Documentation includes the same best practices as
a structure fire: photographing fire patterns, photographing all
evidence items in place, creating necessary diagrams with all
features and sampling locations noted, and keeping an evidence log.
Aerial photographs may be particularly helpful in a wildfire
With preservation, observation, and documentation
underway, the systematic approach for evaluating the scene is the
same as for a structure fire: determine area of origin, then
determine cause and chain of events. Determining origin is often a process
of tracing back the fire flow from the front of the fire to the area
of origin. To assist the investigator, there are numerous indicators
of how the fire spread and which direction it came from. Because so
many factors influence a wildfire and interact to produce different
effects, the investigator should seek to establish a pattern of
indicators and evidence, not solely one factor. In addition, maintain
an open mind about what you see and follow where it leads you. Change
the theory to suit the facts, dont change the facts to suit the
Analyzing Wildland Fire Flow
Timothy G. Huff, former Chief Law Enforcement
Officer for the CA Department of Forestry and Fire Protection and
former arson profiler for the FBI, notes that even though
investigating wildland fires can seem a daunting task, it's a process
that yields results. Huff says, "The fastest way to narrow the
origin of a large fire is to find witnesses who saw the fire in its
early stages, which can include responding firefighters and passerby
witnesses. Beyond that, by the use of indicators, you can track the
fire back to the area of origin. These indicators include impingement
of flame, char, and soot patterns on natural and man-made objects.
You track back those gross indicators to an area of origin, then you
get on hands and knees and are looking at minute features like grass
stubble and pebbles. Once you get it down to an area about the size
of a tabletop, then you are looking for very fine indicators of
cause, like matchsticks, cigarettes, fulgurites from lightning, or
metal flakes from tailpipe exhaust."
Let's break down this process.
Pictured above: Damage after the
Willie Fire (Red Lodge, MT). Photo credit: Karen Wattenmaker. Photo
courtesy of the National Interagency
When analyzing fire flow, investigators refer to the
"fire head" and "fire heel." The fire head is the
portion of the fire moving most rapidly, and generally is the most
intense. Fire heel is at the opposite side of the fire head.
According to NFPA 921
, the fire at the heel is less intense
and will generally be "backing," or burning slowly against
the wind or downhill.
According to NFPA 921, starting from the
outer limit of the fire and interpreting directional indicators such
as burn patterns and char patterns back to the point of origin is the
accepted technique in wildfire investigation. NFPA 921 lists
nine major visual indicators of the direction of fire spread:
- Wildfire "V"
patterns. A wildfire "V" pattern is not the same as
a "V" pattern in a structure fire. A structure fire
"V" pattern is generated by a plume of flame spreading
vertically from the base of the fire. In a wildfire, the
"V" pattern is a horizontal burn on the ground's surface,
where the base of the "V" may be the point of origin. The
pattern is affected by wind direction, slope, and other factors.
- Degree of damage. Fire
intensity and direction can be gauged by the degree of damage to
fuels. Damage to vertical items like trees will be greater on the
side from which the fire approached. Therefore, the direction the
more damaged sides face points toward the area of origin. However,
this indicator is not absolute. Timothy G. Huff asserts, "In a
fast moving fire or one burning upslope, a wrap-around effect on the
far side of the tree may be noted."
- Grass stems. Fire burns the
grass stem bases first and the stalks fall over because their weight
is no longer supported. Stalks that fall forward are subsequently
consumed as fire moves over them. Stalks that fall backward sometimes
remain unburned and generally point in the direction that the fire
approached. However, the direction of fall may be influenced by wind
and should not be taken as the single absolute indicator. Walking in
the direction the unburned stalks point can bring the investigator
closer to the area of origin.
- Brush patterns. When fire
starts in ground fuels, as many wildfires do, it takes a period of
time for that fire to generate enough heat and intensity to spread to
aerial fuels. Therefore, at the back edge of the fire, which may be
near the point of origin, less upper foliage may be burned than at
the front of the fire. In addition, at the back edge, there may be
upper branches that have fallen to the ground unburned because the
fire under them, which had not yet reached the treetops, burned away
the support for the upper branches.
- Ash deposits. Ash can
assist the investigative interpretation in several ways:
- The pattern of ash dispersion can
assist in determining wind direction.
- The amount of ash can indicate
the relative amount of fuel load.
- Where ash fell on intact fuels
may assist the investigator in determining the sequence of the
Cupping. If a fire burns away
the tree trunk, the remaining stump will be "cupped" on the
side facing the fire (see Fig. 13). The sharpened point will
be on the side away from the fire's approach; thus the cupped sides
face in the direction of the fire origin. This effect can be seen on
many types of vegetation, including grass. On grass, the protected
side can be felt by rubbing the hand against the grass. When rubbed
in the direction the fire burned, the grass feels velvety.
Pictured above: Cupping
behavior in a fallen log involved in the Mineral Primm Fire. Note the
ash and soot deposits in front and the green vegetation of an
unburned area behind. Photo credit: Karen Wattenmaker. Courtesy of
Rockies Incident Information Center.
- Die-out pattern. As the
fire dies, there is less damage and charring. Thus, moving into the
more damaged areas from the die-out edges brings the investigator
closer to the fire origin.
Charring and tree damage. Charring is
deeper on the side of the fuel facing the oncoming fire because that
side faced the heat of the fire (see Fig. 14). Relative char
depth can help the investigator determine which side is more charred.
If the investigator puts the deeper char to his/her back and walks,
they are walking toward the origin of the fire. The same is true of
destruction of vegetation; it will be more severe on the side the
fire approached from. As fire spreads up a tree, the wind will drive
the fire away from windward foliage, leaving it less damaged.
Sometimes, the treetops may have a triangular unburned area on the
approaching fire side. Fast moving fire can "bevel" the
ends of branches, blunting branches on the approach side and tapering
branches on the other side. Walk in the direction the rounded
branches point to walk toward the fire's origin.
Pictured above: Damage after
the Pinion Ridge Fire. The yellow arrow points out the char on one
side of the tree trunk. Photo credit: Kari Brown. Photo courtesy of
the National Interagency Fire
The char patterns on the tree trunk can assist in determining
wind direction, which will help interpret patterns and trace fire
spread. The following diagram shows how this works:
- Patterns on unburned items.
Direction of fire travel and intensity may be indicated by
sooty deposits left on unburned and/or noncombustible items. These
indicators can be protected items and patterns, heavier staining and
sooting on the side of an item that faced the approaching fire, and
loss of material as indicated by lines of demarcation. The heat
damage on non-combustibles will be greater on the side from which the
fire approached because the object shields the back of the object.
Non-combustibles can include signs, rocks, steel fenceposts, and
stone walls. Very large noncombustibles can provide a barrier to fire
movement, protecting the items and areas behind them.
- Contradictory indicators.
Contradictory or confusing indicators are often present close
to the fire origin because, at the time they were created, the fire
was undeveloped and had not yet established a direction. Fire damage
may be close to the ground only and items may be only partially
burned in strange ways.
As the investigator analyzes the fire flow and
comes to understand the scene, possible items of evidence may come to
light. A full scene search of the area of origin should be conducted.
The search of the fire scene must be conducted using a systematic
method suitable for an open area, such as a grid method or line
method. As with any search, the search team should mark evidence with
a flag or cone as they encounter it, then move on. More experienced
investigators can then evaluate each marked item and determine if it
should be collected. Timothy G. Huff characterizes the evidence
search as "hands and knees, looking for very small indicators
and items of evidence." Evidence collection procedures are the
same as for structure fires. Photographic documentation and logging
should continue throughout the examination and evidence search. All
indicators and collected evidence should be mapped onto a sketch.
Multiple sketches may be required, depending on the case.
It may seem that searching for evidence of the
fire's cause in a large blaze is looking for a needle in a haystack.
But that needle can be found. Paul Steensland, a senior special agent
with the U.S. Forest Service, found "...three matches stuck
head-first into the ground, spaced a half-inch apart," at the
point of origin of the Hayman Fire, which burned 137,000 acres and
destroyed 133 homes southwest of Denver, CO (Inland
Valley Daily Bulletin, 1 November 2003). Investigators believe
that Terry Barton, a former Forest Service seasonal worker who
pleaded guilty to starting the Hayman Fire, put the matches in the
ground. Even after that devastation, the evidence was still there.
Sources of Investigative Information
In addition to the physical evidence of the burn,
there are many other sources of investigative information:
- Witnesses to the incipient fire.
Witnesses who are present when the fire starts and/or those
who first report the fire may have seen it in its early stages and
can provide information on the physical characteristics of the fire,
anyone else seen in the area, and the location and behavior of the
- Other witnesses who
observed the fire, persons in the vicinity of the fire, and
situations and events surrounding the fire.
- Neighbors and persons familiar with
the area where the fire started. These persons can provide
information on and facts about that area, including common and
uncommon activities in and uses for the area of origin. For example,
they may know that the area is a popular off-roading destination or
that cars are rarely seen there or that teenagers often build
bonfires and holding drinking parties.
- Agencies responsible for tracking
fires, predicting weather, and recording natural disasters.
Wildland fires may be caused by lightning, natural disaster,
or other Earth event. All possible natural causes must be considered
and eliminated. Data collection agencies can provide the necessary
information to determine if a natural cause might be possible. NOAA
can advise on lightning strikes, and U.S. Geological Survey can
provide data on natural disasters, including volcanic activity.
- Utility companies. Fires
can be sparked by utilities equipment, including electricity, gas,
and oil. Two common causes are electrical power lines being downed by
weather and transformer malfunctions that shower flaming and/or
sparking debris to the ground. Check with the utility companies to
determine if a malfunction occurred in the fire area and how it might
have caused ignition.
- Private and commercial
pilots. Often, wildland fires are initially spotted by
pilots, who then report them to the tower. In addition, pilots have a
unique perspective on the development of the fire because they view
it from the air. Record aircraft information, including N-number
(visible on the side of private planes) of any aircraft seen in the
area. Follow up this information with the local airport and inquire
about who was flying at the time of the fire, using the logs to
determine who the pilot(s) were. Then, contact those persons for an
interview. Be aware that arsonists have been known to set wildland
fires from an aircraft.
Aerial surveillance such as satellite
imaging, video reference footage taken from aircraft, and infrared
imaging can provide a visual record documenting the fire's
development and may assist in determining the area of origin and
pattern of fire spread (see Fig. 15).
- Professionals who responded to the
fire. The observations and actions of professionals who
respond to the fire can provide key insight into the fire's
characteristics, movement, and behavior. Professionals may also have
seen persons, vehicles, and activities in the fire area that may
provide the investigator with facts about cause and responsibility.
Professional interviewees should include:
- The first responding unit, which
may be law enforcement or fire
- The initial attack crew
- Airborne responders
- All professionals who spoke with
and/or interviewed witnesses
A Note on The Role of First Responders
As with a structure fire, first responders have a
unique opportunity to observe the fire in its most pristine state.
First responders should note:
- Which fuels are burning
- The direction the fire is moving
- The speed the fire is moving
- Wind direction and estimated speed
- Where the perimeter of the fire is (if
possible, establish landmarks on the perimeter)
- The physical characteristics of the fire
(color of flame, color of smoke, odors, height of flame)
- What persons are in the area, their
descriptions, and their direction of travel. If possible, obtain
their contact information and a description of what they saw
- What vehicles are in the area (both on
the ground and in the air), their descriptions, their tag numbers,
and their direction of travel
- Any possible fire causes and their condition
First responders can also, if their duties permit, assist in
- Encourage responding fire companies to
employ the suppression limitation activities described in the
"Influence of Wildfire Suppression Tactics" section of this
- If possible, mark the potential area(s)
of origin and advise law enforcement and firefighters to avoid them
in an effort to preserve evidence.
- Set up a patrolled perimeter marked by
physical barrier (such as tape) to keep onlookers out of these areas.
- As practical, avoid potential evidence
areas (often those closest to the heel of the fire and where the burn
began, as well as near access points like roads), minimizing foot
traffic and equipment.
- Exercise care in moving equipment. This
will minimize damage to fire patterns and potential evidence.
- Notify the Incident Commander if you
observe any possible pieces of evidence, strange events, or unknown
persons and vehicles.
Keys To Effective Wildland Fire Investigation
Although wildland fire investigation involves
different fuels, different indicators, and different fire spread
principles than a structure fire, the same strong investigative
principles still apply. The following keys to effective wildland fire
investigation will help all investigators determine origin and cause
with greater accuracy.
Appropriate Training. The typical
fire investigator probably sees mostly structure fires. Therefore,
the investigator may have little experience with a wildland fire
investigation when called upon to undertake it. According to Timothy
G. Huff, "Experienced structure fire investigators will quickly
adapt their knowledge of structure fire spread indicators, like char
patterns and soot deposition, to the wildland fire. However, some
aspects of wildland fire investigation can be tricky, like backing
fires vs. running fires, so the investigator shouldn't assume they
are prepared for the wildland fire investigation." Training in
wildland fire investigations will better prepare the investigator to
decipher what they will see in an open area fire. As always, if the
investigator feels that the investigation is beyond his or her
capabilities, the most important step they can take is to call upon
expert resources for assistance.
A Systematic Approach. The
investigation of a wildland fire can be approached with the same
basic protocol as a structure fire investigation. A systematic
approach like the one presented in interFIRE VR includes tasks such
as securing the scene, preserving evidence, making documentation,
interviewing witnesses, searching for and collecting evidence,
analyzing the fire flow, eliminating all potential accidental causes,
and determining cause and origin. Depending on the phase the fire is
in when the investigator arrives, the order in which tasks are
completed can be adapted. For example, if the fire is still actively
involved and entrance into the area of origin is not possible, begin
with taking witness information, vehicle tag numbers, and similar
Keen Observation. Many wildland
fires leave devastation in their wake. However, not everything is
necessarily destroyed. "Surprisingly, matches are not fully
consumed by wildland fires," states Huff. "You can find
them, but you have to get on your hands and knees and look very
closely." Keen observation, and patience in applying it, will
help the investigator find the needle in the haystack.
Documentation. Huff advises that
documentation is key to an effective wildland fire investigation,
"Photographs, sketches, evidence collection and chain of custody
documentation are all are necessary."
Local Knowledge. Get to know the
area and what goes on there. Ask witnesses, nearby residents, and
recreationers what goes on in that area, both legal and illegal.
Learn the patterns of utilities, machinery, vehicles, and other
potential sources of ignition. If possible, track what happened in
the time before the fire. Ask questions like: was someone camping in
the area? was there a lightning strike? did the utility company
report equipment issues? was there a motor vehicle accident? did a
train travel through? Think through all these possible sources of
ignition and do the homework necessary to eliminate or substantiate
each potential cause.
Common Sense. Apply common sense to
the fire indicators you see to develop and test possible theories. If
the fire started near the roadside, think through how someone could
have accessed the area and examine the routes of access for
footprints and tire prints. If the fire origin is near equimpment,
investigate how it might have been involved. Travel as many avenues
as necessary. Huff notes, "Sometimes, even if you do all your
hands and knees examining, you don't find anything. If the
investigator is thorough and there's nothing there, think about the
possibility that the fire was set with something that was taken away
from the fire scene, such as a cigarette lighter."
Investigating wildland fires can be a departure
from the regular routine of examining structure fires. In addition,
many wildland fires that investigators see will be small, far smaller
than the massive wildland fires many associate with the Western U.S.
However, investigation of every fire is important; a small fire may
be a starting point for a serial arsonist, or may be an indication of
a potentially catastrophic equipment failure, or a harbinger of a
safety hazard. Understand the basics of wildland fire dynamics and
the requirements of the investigation. Apply your systematic
approach, and don't hesitate to call for assistance. Huff is
practical about wildland fire investigation, "Be prepared for
that period of confusion, when you are seeing a lot of things that
don't make sense immediately." Take the time and care to work
through this confusion and sort out where the indicators point you.
Most of all, know when to ask for help. There are investigators with
significant expertise in wildland fires who can provide assistance.
Contact your State Fire Marshal's Office or State Department of
Forestry for more information.
Case studies of wildfires can provide a good
learning experience in wildland fire causes, fire dynamics, and fire
investigation. Wildland fire case writeups available online
CA, 10/21/91." NFPA.
Bridge Road Fire, Crawford, MI, 5/8/90." NFPA. Firewise.org Library Item 0188.
Storm 91, Spokane, WA, 10/21/91." NFPA. Firewise.org Library Item 0197.
Fire, Boulder, CO, 7/9/89," NFPA.
of Forest Fires in South Dakota's Black Hills National
Forest." NFPA, 2003.
Cook, Rick. "Show
Low, Arizona, Inferno: Evacuation Lessons Learned in the
Rodeo-Chedeski Fire." NFPA Journal. March/April
Special Report: Wildland Fires Video." NFPA (25 minute video
case study of three wildland fires).
Michaels, Mark. "On the Job:
California-Oakland Hills Fire Storm." Published in Firehouse Magazine. Dec 1991. Firewise.org Library Item
"Oakland/Berkeley Hills Fire, October 20,
1981." Published on firewise.org. Firewise.org Library Item
Butler, Bret W. et. al. "Fire Behavior
Associated with the 1994 South Canyon Fire on Storm King Mountain,
Colorado." USDA-Forest Service. Published by the Rocky Mountain Research
Station. 1998. Firewise.org
Library Item 00201.
O'Driscoll, Patrick and Kenworthy, Tom. "The
Los Alamos Fire, Repeats waiting to happen all over the West" by
. Published by USA Today, May
15, 2000. Firewise.org Library
Graham, Hugh W. "Urban Wildlands Fire -
Pebble Beach, CA, May 31, 1987." U.S. Fire Administration. 1997.
Firewise.org Library Item 00198.
"Thirty Mile Fire Investigation - Accident
Investigation Factual Report and Management Evaluation Report."
Published by the USDA Forest
Service. 2001. Firewise.org
Library Item 0115.
Stolzenburg, William. "Fire in the
Rainforest." Published by The
Nature Conservancy. 2001. Firewise.org Library Item
Dominquez, Roberto Martinez and Martinez, Arturo
Raygoza. "The Worst Fire Disaster in Mexico." Published by
Bombardier Aerospace. 1998.
Firewise.org Library Item
Investigation Documents: Thirty-Mile Factual Investigation Report,
Management Evaluation Report
Grande Prescribed Fire Investigation Report, May 18, 2000
Fire Entrapment Investigation - August 1999
Ranch Prescribed Fire Review - July 2, 1999
Interagency Report on
the South Canyon Fire (6/26/95)
South Canyon Fire
Investigation Report (8/17/94) Executive Summary Only
The author gratefully acknowledges the
contributions of the following professionals to this article:
Timothy G. Huff
Bob Duval, NFPA
Jim Smalley, NFPA
Robert A. Corry
Timothy G. Huff: Biography
Timothy G. Huff is retired from the California
Department of Forestry and Fire Protection and the Federal Bureau of
Investigation. Huff for 10 years specialized in arson and bombing
profiling for the FBI, assigned to Quantico, VA at the National
Center for the Analysis of Violent Crime. Prior to that, he was a
30-year veteran of the California Department of Forestry and Fire
Protection and retired at Chief Law Enforcement Officer. He now is a
law enforcement consultant in California.