Michael Auzenne
Instructor
GCM, CJC
ARSON AND FIRE INVESTIGATION
I.
INTRODUCTION
II.
CHEMISTRY OF FIRE
A.
i.
Oxidation Reaction: The complete or partial loss of electrons or
gain of oxygen.
i.
Combustion Reaction: Oxidation reaction that involves oxygen
and that releases heat and light.
Heat of Combustion: Excess heat that is given off in a combustion
reaction.
Exothermic Reaction: Chemical reaction that releases heat.
Combustion
ii.
iii.
B.
The Fire Tetrahedron
Four ingredients are needed to start a fire and keep it burning:
* Oxygen – a major gas in the air; important ingredient in any combustion
reaction
* Fuel – the material that is burning; the accelerant will burn first followed by
other nearby sources that ignite and become fuel for the continuation of the fire.
i.
Accelerant: In fire investigation, any material used to start or
sustain a fire; the most common are combustible liquids.
* Heat – at or above the ignition temperature, the fuel will continue to burn even
after the heat source has been removed.
i.
Ignition Temperature: The temperature at which fuel will react
with oxygen, or burn.
* Chain Reaction – The fire will usually release enough heat to keep the fire going
and will continue to burn until all the oxygen or fuel is used or removed.
C.
Flash Point and Ignition Temperature
i.
ii.
iii.
D.
Pyrolysis
i.
III.
Hydrocarbon: Any compound consisting only of hydrogen and
carbon.
Vaporization: The process in which a liquid changes to a gas
state.
Flash Point: The lowest temperature at which heat may start
burning to vaporize a liquid.
Pyrolysis: Decomposition of organic matter by heat in the
absence of oxygen.
DIFFICULTIES IN ARSON DETECTION
Arson is a difficult crime to prove because the crime is usually carefully planned, the arsonist has
usually left the scene before anybody notices the fire, the fire often destroys evidence from the
crime, and what evidence is left is often destroyed as firefighters extinguish the fire.
i.
ii.
IV.
Arson: The intentional and illegal burning of property.
Arsonist: The person who intentionally starts an illegal fire that
damages property.
FUNCTION OF A FIRE INVESTIGATOR
There are four categories of a fire:
* Natural – A fire caused by acts of nature; a lightning strike or intense sunlight
* Accidental – A fire that was unintentional and explainable; causes may include faulty
wiring, malfunctioning appliances, or human carelessness.
* Undetermined – The cause of the fire is unknown and cannot be identified.
* Deliberate – A fire was intentionally set (not always arson; a campfire can spread out of
control, for example.)
V.
DETERMINING CAUSE
The point of origin, which can provide clues as to the origin of the fire, will be marked by a burn
pattern. There is often a V-shaped burn near the point of origin. The V-shaped burn is usually
present in cases of natural or accidental fires. However, in cases of arson, other patterns may be
present.
i.
Alligatoring: A burn pattern resembling the scales of an alligator
originating from the point of origin of a fire.
ii.
iii.
iv.
VI.
Concrete Spalling: The breaking away of layers of concrete from
the point of origin of a fire.
Pools: Burn patterns resembling puddles that indicate an
accelerant was poured.
Streamers: Trails of accelerants often used to spread the fire.
COLLECTING THE EVIDENCE
Investigators often collect 3-4 L of ash and debris from the point of origin and anything that could
have traces of accelerants. Investigators also take a debris sample that has not been contaminated
by the accelerant. Each sample is packaged in its own container. Fire debris must be packaged in
an airtight container; otherwise, vapor from accelerants might be lost.
A.
Collecting the Control
i.
B.
Packing the Debris
i.
C.
Headspace: A few inches of space left below the lid of an airtight
container for the collection of vapors from fire debris samples.
Finding the Igniter
i.
ii.
VII.
Substrate Control: A similar, but uncontaminated, sample; used
for making comparisons.
Molotov Cocktail: A homemade, firebomb made with a glass
bottle, fuel, and a wick.
Criminal Profile: A list of characteristics, such as age, gender, and
motives, that help investigators narrow the list of suspects.
LAB ANALYSIS
i.
ii.
Direct Headspace Extraction Procedure: A method used to
analyze accelerant residue from collected debris to determine
exactly what accelerant was used to start a fire.
Passive Headspace Extraction Procedure: A method used to
analyze low concentrations of an accelerant residue from
collected debris that might have been missed during the direct
headspace extraction procedure.
VIII.
PSYCHOLOGY OF AN ARSONIST
The characteristics of an arsonist include:
* Less than 25 years old
* Father not in the home
* Domineering mother
* Academically challenged
* Emotionally and/or psychologically disabled
* Unmarried, possibly still living at home with parents
* Feelings of inadequacy and insecurity
* Fascination with fire
* Alcoholism
* Parental neglect or abuse
IX.
MOTIVES FOR ARSON
A.
Financial Gain
B.
Revenge
i.
C.
Excitement
D.
Vanity
E.
Crime Concealment
F.
Spite Arson: A fire started to destroy an organization or a person
for the sake of a cause.
i.
Crime Concealment: A motive for arson sometimes used to
destroy evidence of another crime.
i.
Vandalism: A motive for arson often used by starting fires in
schools, trash cans, dumpsters, wooded areas, and abandoned
buildings.
Vandalism