Forensic analysis and characteristics of fire and arson.

1. CHAPTER XI
FIRE AND ARSON
INVESTIGATION
ABRENCILLO JONNABELLE M.
PACIA JULIUS ANDREI

2. FIRE ARSON

3. FIRE
Fire is a chemical reaction that produces physical
effect with evolution of heat and light. This reaction is
called combustion.
FIRE INVESTIGATION
It is the comprehensive analytical approach by
understanding the fundamental property of fire by
determining the chemistry of fires,fuels and
combustion.

4. Objective/purpose of Fire Investigation
 To save lives and prevent injuries
 To determine the origin and cause of fire
 To provide proof of fact during trial
 To prepare to detent those conclusion in ratio and logical manner supported by
scientific data
Classification of Fire Investigation
 Natural
 Accidental
 Unknown origin
 Suspicious
 Incendiary (obvious arson)
 Incendiary fire is the largest and most obvious fire investigated. The primordial intent is to
destroy property/ ies of another.

5. “
”
Issues in Fire Investigation
1. Lack of time
2. Misidentified as accidental fire due to lack of experience
3. Intentionally made to avoid complication of identifying a fire
as a criminal act
Arson Investigation
Arson is the malicious burning of dwelling, house or building
of another.
In all fires, there must be a cause before an effect is
produced. This cause is known as combustion.
.

6. Technical Aspects of Arson Cases
 Burning or combustion is the rapid oxidation of substances accompanied by the
generation of heat and light.
 Three (3) essential ingredients are present in Burning FUEL, OXYGEN AND
HEAT
 Create a fire must be combustible materials SOLID, LIQUID, OR GAS. Strictly
speaking only gases burn.
 Solids and liquids must be heated to liberate flammable gases.
Causes of Fire
A fire may be produced intentionally or accidentally. One of the
method of proving arson is to determine systematically the presence of
malice and intent in burning the property of another .
An accidental fire may arise from the working of certain force of
nature or from negligence in the use of equipment and materials.

7. Natural cause of fire
Sunrays are focused by bubbles in windowpanes
shaving mirror or by some other peculiarly shaped
glass article, which may serve as convex lens.
Lightning usually strikes a high point of the building
and may be trace in its path to the ground.
Indication of Arson Fire
 Burning faster and larger than normal
 Often having multiple points of origin
 Use of accelerants
 A time delay devices ( a matchbox and cigarette is a 22 minute
fuse)
 Cans and containers are usually found at the crime scene

8. Heat can be estimated by the condition of
window glass
Small shards of glass mean an explosion took place.
CRAZING means a hot fire
Melted copper, aluminum and other metals usually means
an accelerant was used.
Soot that wipes off easily from glass or slightly charred studs
behind the walls means a quick fire.
Combustion, Nature and Behavior of Fire
Combustion
 Combustion is a burning reaction in which a substance combines with a gas.
 Heat and light usually accompanied by combustion reaction and most of this reaction
involved oxygen.
 Example : Hydrogen combined with oxygen will undergo rapid oxidation and produces
water and heat.

9. Two type of Combustion
1. Flaming- destructive, gaseous
combustion where both the fuel oxidizer
are gases.
2. Glowing- absence of fire but presence of
very hot materials on surface of which
combustion is proceeding.

10. Two kinds of Combustion
Complete Combustion- all of the reactants are
consumed.
Incomplete Combustion- only some parts of
the reactant are consumed.

11. Basic Combustion Condition
 Presence of Combustible fuel
 Oxidizer
 Energy of Ignition (heat) applied
 Interaction of fuel and oxidizer to sustain chain reaction
•Matter- elements and compounds: composed of atoms combined forming molecules
•Air- composed of 21% oxygen and 75% nitrogen
•Oxidation- is a combination of element and compounds with oxygen producing stable
substances. Those compounds and elements that combine with oxygen and produces fire are
called flammable substance and the process is called combustion.
•Pyrolisis- come form the Greek work pyro (fire) and lysis (decompose)
- process of decomposition of material to simpler compounds brought about by heat
from fire.
Flame- is a gaseous reaction where plume of hot gases rises by convection when air and its
oxygen is maintained by solid (soot) or liquid (aerosol) in a closed room.

12. Theoretically,
 If oxygen falls below 15%, combustion rate decreases.
 If the temperature reaches 900-1000 degree C, post flashover room fires which oxygen
concentration is only 5-8%.
 If 0-5% and the temperature reaches 1000 degree C-flaming hot.
•Nitrogen, N – presence of nitrogen helps/ delivers extra oxygen to continue the
combustion reaction.
EXAMPLE: Presence of Nitrates (NO3) is fuel
Color Temperature of Incandescent Hot Object (Glowing Fire)
1. Dark Red- 500 to 600deg C
2. Dull Red- 600- 800deg C
3. Bright Cherry Red- 800-1000deg C
4. Orange- 1000- 1200deg C
5. Bright Yellow- 1200- 1400deg C
6. White- 1400 – 1600deg C

13. Fire Triangle
 Fuel
 Heat. Ignition
 Oxidant
Explosive Triangle
 Fuel
 Ignition
 Oxidant
FUEL IGNITION
OXIDANT

14. Color of Smoke and Odor being evolved
 White – humid materials
 Light gray – hay and vegetable matter
 Black – lack of air with huge flames usually petroleum based.
 Reddish brown/ thick yellow/ brownish yellow- nitrocellulose fires, sulfur
and sulfuric, nitric, or other chemicals.
 Bitting smoke – indicates the presence of sulfur
 Rotten – cabbage like odor- indicates the presence of carbon disulfide
 Garlic odor – indicates the presence of phosphorous

15. Application of Heat to Fire Investigation
 Heat as applied for igniting fire
 Heat as applied for increasing rate of chemical reaction
 Transfer of heat
Transfer of heat
 Conduction – transfer by contact between moving molecules from hot to cold areas
 Convention – distribution of heat by circulating medium
 Radiation – critical where it aids fire to spread and promotes ignition of other fuels.
Two types of heat reaction
 Exothermic – heat is released from the system
 Endothermic – heat is absorbed to the system

16. Sources of Ignition
Ignition involves burning the fuel to characteristic temperature by
convection, conduction or radiation of heat until it can sustain
combustion.
Sparks / Arks
Primary Igniters
Lighters
Hot object / Surface
Friction
Primary Igniters
Matches – is the common device for kindling a flame.It iis composed
of combustible materials combined with head containing both fuel and
oxidizer that can be ignited by friction.

17. Two types of primary igniters
1.Strike anywhere/kitchen match – the tip contains a high percentage of
phosphorous sesquisulfide (P4S3) and ground glass.
 Component: oxidant = Potassium Chlorate
 Fuel =Sulfur or paraffin + binder or glue + filler ( silica)
2.Safety match – will ignite only using abrasives ( rough) materials
 Component : Oxidant = Red Phosphorous
 Fuel : Sulfur
Lighters
 Lighters can explode when exposed to a high temperature and form a leakage when
exposed to a reduced atmospheric pressure such as airplane.
Two types of lighter:
 Electrical/ element type – electrically connected to a battery of vehicles, current,
etc.
 Liquid fuel lighter – contain liquid butane or light petroleum as fuel in a
compartment under pressure.

18. Sparks/Arks
 Can be produced using electrical current discharging through the air or insulator, or tiny fragment of burning or
glowing solid.
Hot object/Surface
 May convert the fuel to vapor which eventually starts a fire
Friction
 Friction between two moving object/ surfaces generates heat.
 Example : brake shoes of automobiles can become extremely hot
Other sources of Ignition
 Radiant heat
 Chemical reaction
 Other source: fireplace and chimneys
 Trash burners and bonfires
 Hot/molten metals
 Mechanical sparks
 Firearms residue: during discharge of riffle flakes escaping from the muzzle of a short barrel handgun is burning.
These flakes can ignite finely divided cotton and similar combustibles at vey close range (1 to 4 feet)
 Smoking, lightning, spontaneous combustion ignition of electrical linings.

19. LABORATORY IDENTIFICATION
Recognition, Collection and Preservation of
Physical evidence
 In recognition fire, identify first the origin. In this case, many
evidence can be recovered such as partially burned and
unburned fuels. This is usually trapped in crevices or under the
collapsed chimneys , etc.
 In collecting physical evidence such as debris, use your
nose if a vapor detector is not available. Collect as many as you
can until the container is completely filled. If the container is
completely filled with debris evaporation of volatile accelerants
will be prevented even if the container is opened.
 Preservation: usual container used is unused metal paint
cans or glass with a screw cap.

20. Laboratory Examination
Color test using Sudan Black.
 In this method of examination , the accelerants are allowed to evaporate
and the vapor are reacted with this chemical until pink color of solution
will appear which indicates the presence of any accelerant.
Confirmatory examination: Gas chromatography
with headspace
 This analytical method is used to detect the specific volatile accelerants
by comparing it with known standard such as kerosene, gasoline , etc.
How to minimize the fire
Fire incidents can be prevented by:
 Better building design
 Fire safety practices