Transcript Document

Arson
Fire Debris Assay
Frank J. Padula
FIC
NYSP
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 Arson is defined as purposely
setting fire to a house, building or
other property.
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Arson Statistics
Rules of Fire Origin
Arson is the second leading cause of death by fire.
Estimated 500 Americans die in arson-related fires.
Arson causes more than $2 billion in property damage.
Only 19% of arson cases resulted in arrest;
Only 2% were convicted.
50% of arsonists -- under age of 20
(40% are under 15 years old).
Fire burns up and out (v-pattern).
Presence of a combustible material is needed.
Needs fuel and oxygen to continue.
Spread influenced by air currents, walls and stairways.
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Definitions.
Flammable liquid.
Ignition temperature and
flash points are NOT
related!
Combustible liquid.
(IN?) Flammable.
Flammable or
explosive limits.
•Liquid
•Flash
Point
•Gasoline
-45oF
536oF to
853oF
•Kerosene
100oF
410oF
Vapor density.
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•Ignition
Temp
Flash Point - temperature at which a particular flammable liquid
gives off vapors (vaporizes) and therefore can ignite.
Ignition 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 i.e.,
lighted cigarette or spark.
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Ignition Temperature
Combustion will continue until:
Fuels are Consumed
Oxidizer is Quenched
Fuels Cooled Below Ignition Temperatures
Flames Retarded.
Transfer of Heat, Types of:
Conduction
Convection
Radiation
Direct Flame Contact
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Class
1. Light Petroleum Distillates (LPD)
2. Gasoline
3. Medium Petroleum Distillates (MPD)
4. Kerosene
5. Heavy Petroleum Distillates (HPD)
6. Miscellaneous
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Light Petroleum Distillates
Produced by distilling crude oil.
From C4 thru C11 range of hydrocarbons.
Representatives: petroleum ether, cigarette lighter
fluid, some camping fuels and solvents.
Gasoline
Refined petroleum mixture of the C4 thru C12 range.
Produced from crude oil using ‘cracking and reforming’.
All brands / grades of automotive gasoline fit within this.
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Medium Petroleum Distillates
Produced by distilling crude oil.
From C8 thru C12 range of hydrocarbons.
Representatives: paint thinners, mineral spirits, dry
cleaning solvents and charcoal starter containing
mineral spirits.
Kerosene
Produced by distilling crude oil.
From the C9 thru C16 range of hydrocarbons.
Representatives: kerosene, jet fuel, and lamp oils.
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Heavy Petroleum Distillates
Produced by distilling crude oil.
From C10 thru C23 range of hydrocarbons.
Representatives: diesel, lamp / home heating oils.
Miscellaneous
Produced by collecting - recombining certain fractions
of distilled crude oil.
From a wide range of hydrocarbons.
Representatives: brush cleaners, thinning agents,
strippers, products for home, auto--industrial use.
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Point of Origin (POO).
Where the fire originated.
Cause of fire may be near ...
Fire usually burns longer at
...
If accelerants / ignition
devices used; may be
present ...
Multiple POO’s MAY indicate
arson.
“V” patterns usually point
here.
Extensive ceiling damages
may be present above ...
Interior Examination.
Work backward in relation
to fire travel and from least
to most damage.
Ceiling damage may lead
to POO.
In accidental fires, floor
damage is limited in
respect to the ceiling
damage.
“V” patterns may help
locate POO.
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Evidence of Accelerants
Large amounts of damage.
Unusual burn patterns.
High heat stress.
Multiple sites of origin.
“Sniffers”
Portable GC
Chemical Tests
Canines
Portable Detectors
Detect O2 level on a
Semiconductor
Guides to the best place to
collect samples
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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.
Investigation of Vehicle Fires
Vehicular fires are investigated just as structural fires.
Accidental fires tend to be isolated to one area of the vehicle.
Incendiary fires tend to consume the entire vehicle; are very
hot.
The loss of temper of the seat strings may be observed.
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Steps to Recover and Identify Accelerants
Collect samples.
Extract the fire debris.
Carry out instrumental analysis.
Interpret the results .
The evidence container should have the following qualities:
Air tight
Highly resistant to breakage
Prevents cross-contamination
Good integrity seal
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Collection of Evidence
First, search looking for objects that do not seem to belong.
Concentrate where the suspected accelerant container was
found.
Store the samples in containers where they will not be
contaminated.
Common Sampling Errors
Insufficient sample
Taking samples from the wrong places or materials
Ineffective sample preservation techniques
No comparison samples
Not maintaining an evidence “chain of custody”
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Identification consists of three steps:
Sample preparation
Instrumental analysis
Data analysis
Common methods used today:
Steam distillation
Vacuum distillation
Solvent extraction
Charcoal sampling
Swept headspace .
The paint can containing the debris is identified by a unique
case and item number. DFLEX inserted.
The can is put into the oven and heated.
After heating, the DFLEX are put in separate glass vials.
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The vial is automatically injected on the gas chromatograph /
mass selective detector (GC/MSD).
The GC will separate all of the sample’s substances.
The MSD will identify the sample’s substances.
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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.
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The Argon Fluoride Excimer LA ICP MS-DRC:
To Combat
Clandestine Methamphetamine Labs
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Laser Ablation Goes Primetime
Fremont, Calif., November 29, 2004 - CSI: Crime Scene
Investigation, the hit TV show about a team of forensic
investigators who use both cutting-edge scientific methods and oldfashioned police work to solve crimes, recently tapped Laser
Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) to crack a particularly tough case. In the recent episode,
“What’s Eating Gil Grissom”, investigators are stumped by a crime
scene consisting only of human-skeletal remains when they finally
get a break: they discover a near-microscopic blue chip among the
remains.
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The problem is, the sample size is far too small for the capabilities
of conventional forensics techniques. Instead, they employ a laserablation microscope; it has no problem identifying the material: a
shard of human fingernail smeared with blue paint and motor oil.
Eventually, the evidence is crucial to unlocking the case: the killer’s
M.O. is to apply blue paint to a staircase railing, using motor oil to
retard the drying process. He waits for the female victim to touch
the railing and when she attempts to wash the paint off her hand,
he attacks. “Standard forensics techniques typically involve
extensive sample preparation and hazardous substances. This can
introduce contamination and destroy large amounts of a sample. In
contrast, ICP-MS requires only a minute sliver of the sample.”
In ICP-MS, a pulsed laser vaporizes a minute amount of a solid
sample. A gas stream carries the sample vapor into a hightemperature plasma where it is ionized before extraction into the
mass spectrometer for analysis.
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The problem with gas chromatography and
mass spectrometry, however, is that in order to
analyze evidence, you have to destroy it—which
means investigators have to get the test right the
first time, or the perp might walk.
Laser ablation etches off only a tiny slice of a
sample with a needlelike light beam and cooking
it in a plasma furnace equipped with a mass
spectrometer especially sensitive to trace
elements.
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