Transcript Arson Investigation - St. Edward's University

ArsonAnalysis of Fire
Arson is defined as purposely setting
fire to a house, building or other
property.
Arson is the second leading cause of
death by fire in the U.S. An estimated
500 Americans died in arson-related
fires.
Arson caused more than $2 billion in
property damage.
Only 19% of arson cases resulted in
arrest, and only 2% were convicted.
50% of arsonists are under the age of
20 (40% are under 15 years old).
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Ignition temperature.
Combustion will continue until:
1.
2.
3.
4.
Fuels are consumed.
Oxidizing agent has been removed.
Fuels are cooled below their ignition
temperature.
Flames are chemically retarded.
Transfer of heat. :
Conduction.
Convection.
Radiation.
Direct flame contact.
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Definitions.
Flammable liquid.
Combustible liquid.
Ignition temperature and flash
points are NOT related!
•Liquid
•Flash
Point
Flammable or
explosive limits.
•Gasoline
-45oF
536oF to
853oF
Vapor density.
•Kerosene
100oF
410oF
Flammable.
•Ignition
Temp
Flash point - The temperature at which a particular flammable liquid
gives off vapors (vaporizes) and therefore can ignite.
The ignition temperature is the temperature required for a liquid to
continue to emit vapors that can sustain
combustion.
A flammable liquid in its liquid state will not burn. It only will
ignite when it vaporizes into a gaseous state. All flammable liquids
give off vapors that can ignite and burn when an ignition source such as
a lighted cigarette or spark is present.
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Point of Origin (POO).
Defined as where the fire originated.
Cause of fire may be near the POO.
Fire usually burns longer at POO.
If accelerants or ignition devices
used, they may be present at the
POO.
Multiple POO’s MAY indicate arson.
“V” patterns usually point to the
POO.
Extensive ceiling damages may be
present above the POO.
Point of Origin (POO).
Interior Examination.
Work backward in relation to
fire travel and from least to most
damage.
In accidental fires, floor damage
is limited in respect to the
ceiling damage.
“V” patterns may help locate
POO.
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Metal
Solder
Tin
Lead
Zinc
Magnesium
Aluminum
Silver
Gold
Copper
Iron
Chromium
Melting Temperature, oF
361
449
618
878
1202
1220
1761
1945
1981
2781
3497
Accelerants
Accelerants are any liquid, solid or
gaseous material that will sustain or
enhance flammability.
Liquid materials are commonly used
because of ease of ignition and
familiarity of use.
Accelerants are nearly exclusively
derived from hydrocarbons.
Straight chain hydrocarbons are the
backbone of the oil industry.
Hydrocarbons are molecules made up of
the elements hydrogen and carbon.
Octane is a term familiar to all. It
consists of a hydrocarbon having 8
carbons.
Examples:
Gasoline
Kerosene
Diesel
Lighter fluids
Charcoal starters
Automobile additives
Camping fuels
Classification of
Accelerants
1. Light petroleum distillates
(LPD)
2. Gasoline
3. Medium petroleum
distillates (MPD)
4. Kerosene
5. Heavy petroleum distillates
(HPD)
6. Miscellaneous
Evidence of Accelerants
Large amounts of damage
Unusual burn patterns
High heat stress
Multiple sites of origin
“Sniffers”
Portable gas chromatographs
Chemical tests
Canines
Portable detectors
Detect change in oxygen level on a
semiconductor
Guides to the best place to collect
samples
Dogs can detect 0.01 mL of
50% evaporated gasoline
100% of the time.
0.01 mL is about the size of
a thousandth of a drop.
Steps to Recover
and Identify
Accelerants
Collect samples.
Extract the fire debris
and obtain a sample
for instrumental
analysis.
Carry out instrumental
analysis.
Interpret the results.
Evidence
Containers
The evidence container should have the
following qualities:
Air tight
Highly resistant to breakage
Prevents cross-contamination
Good integrity seal
Accelerant Identification : Extraction
Common methods used today:
Steam distillation
Vacuum distillation
Solvent extraction
Charcoal sampling
Swept headspace .
Analysis
The vial is automatically
injected on the gas
chromatograph / mass
selective detector
(GC/MSD).
The GC will separate all
of the sample’s
components.
The MSD will identify
the sample’s components.
A gas chromatograph
is coupled to a mass
selective detector.
An Ignitable Liquid
Is Detected
“Sample contains a medium
petroleum distillate (MPD),
some examples are paint
thinners and mineral spirits”.
“Sample contains a mixture of
gasoline and a heavy petroleum
distillate (HPD). Some
examples of a HPD are diesel
fuels and heating oils.”
No Ignitable
Liquids Were
Detected
We can look at this in four different
ways...
No ignitable liquids were ever used
Ignitable liquids were used to start the
fire, but have been totally consumed.
Ignitable liquids are still present;
however, not in the collected sample.
Ignitable liquids are still present in the
collected sample; however, they are
too dilute to be detected.