Fire Debris, Fire Investigations and the Forensic Lab - Are We Missing Things? Or, Keeping Up with the Dogs

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Fire Debris, Fire Investigations and the Forensic
Lab -Are We Missing Things? Or, Keeping Up with
the Dogs

• Dr. John D. DeHaan

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The need for science in fire scene investigation

• Started to change in the 1980s with new,
  science-based texts and a growing awareness of
  the need to get it right.
• NFPA began the process to create the 921 Guide
• Court decisions (Daubert, Kumho, Joiner,
  Benfield, et al.) forced fire investigation to
  become more science-based.
• The Scientific Method is expected.
• Experts Have to Support Their Conclusions and
  demonstrate reliability, acceptance, and use of
  published, peer-reviewed data.

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Fire Investigations and the Forensic Lab

• If the investigator has no access to reliable
  answers based on good science, he or she will
  turn to less reliable sources such as those the
  oral history promulgated (often erroneously).
• The answers needed by todays investigators go
  far beyond Was there an ignitable liquid in the
  debris?

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CRIMINALISTICS
Purpose Aid in Reconstructing Events and Human
Activities Link suspect and
scene or victim and suspect

• Debris containing suspected volatiles
• Liquids
• Charred or burned paper documents
• Clothing and shoes
• Tools and tool marks

• Dry blood stains
• DNA/saliva
• Glass fragments
• Paint chips
• Hairs and fibers
• Firearms

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Debris containing suspected volatiles

• The most requested service
• Well-studied and Documented by ASTM practices
• Isolation of volatiles from debris
• E1386 Solvent extraction
• E1388 Headspace sampling
• E1412 Passive headspace (C-strip)
• E1413 Dynamic headspace (charcoal tube)
• E2154 SPME

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Method Selection

• E1412 Most commonly used, easy, low cost,
  non-destructive, wide dynamic range
• May miss light ends (Hydrocarbons under C7) if
  sampling time is too long
• May miss heavy ends (hydrocarbons over
• C18) if sampling time is
• too short or temperature
• is too low
• Uses solvent extraction
• from carbon strip

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Gas Chromatographic Analysis

• ASTM E1387
• GC-FID Characterization by peak pattern and
  retention times
• Original method low cost, universal range
• Well-suited to gasoline, paint thinner,
  kerosene, diesel, light distillates, and
  miscellaneous class blends and non-distillate
  products
• Proliferation of new custom petroleum products
  and non-petroleum products
• De-certified by ASTM E-30 in 2010

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Gas Chromatographic Analysis

• GC/MS became necessary to make many
  identifications
• First published as ASTM E 1618 in 1994
• Capable of separating aliphatics, aromatics,
  cycloalkanes, and unsaturated compounds
• Retention times, peak profiles, target compounds,
  aromaticaliphatic ratios are now criteria
• Now multiple classifications seven major
  classes, divided by boiling point range, plus
  automotive gasoline, for a total of 21.
• E1387 dropped as a recommended method in 2010.
• Heavy products no longer separated into kerosene
  class v. fuel oil class

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GC/MS The Only Answer?

• With solvent injection methods, most GC/MS
  operators sacrifice all peaks that elute before
  the solvent (diethyl ether, dimethyl ether, or
  carbon disulfide)
• This means that many
• light products including
• ethers, ketones, alcohols
• and C6 range hydrocarbons
• are not recorded.
• These may be critical to
• the evidence.

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Jumping straight to selected ions

• The overall pattern of peaks is very important in
  the characterization process
• Start with the TIC!
• Skipping straight to looking for aromatic v.
  aliphatic peaks or even target compounds can
  result in misleading conclusions

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Blind Spot

• Because the heavy distillates are no longer
  split, it is OK to report heavy petroleum
  distillate and list kerosene and diesel fuel as
  candidates
• This has led to mischaracterization of kerosene
  as diesel fuel and
• vice versa (not by the analyst
• but in court by the investigator
• or the prosecutor).
• The analyst has to know what issues are important
  and modify the technique used.

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Lab Analysis

• Not just for Volatile Accelerants!
• Identification of Fuels
• Laboratory Identification
• By chemical, physical, or microscopic methods
• Field Tests
• Fire Tests

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Fire Investigations and the Forensic Lab

• Furnishings and Clothing
• Are they natural fibers cotton, linen, wool?
• Are they synthetic polyester, polypropylene,
  nylon, acrylic, or ???
• Are they thermoplastic, or thermosetting, or
  elastomers?
• Melting points? Ignition temperatures?
• What volatile products do they generate?
• Foam polyurethane, polyether, or latex?
• Are there fire retardants present?

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What Can the Lab Tell?

• General type of fuel may help identify or exclude
  competent ignition sources.
• Is the Fuel First Ignited Cellulosic?
• Cellulosic Derived from Plants
• Wood
• Paper
• Cotton
• Linen
• Cardboard
• Susceptible to smoldering
• Crumbly grey/black ash on burning
• White smoke

Cellulosic fuels are susceptible to hot
surface/glowing ember ignition
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What Can the Lab Tell?

• Is the Fuel First Ignited Synthetic?
• Most Synthetics are petroleum derivatives
• Nylon
• Polyethylene
• Polystyrene
• Polyester
• Rarely ignitable by smoldering/hot surface source
• Easily ignited by open flame
• Tend to melt and shrink away from heat
• Most do not sustain smoldering combustion

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What Can the Lab Tell?

• Synthetics
• May be thermoplastic melts without degrading
• May be thermosetting (resin) degrades, chars,
  may smolder
• Other fuel types
• Elastomers (rubbers) Synthetic or natural
• Leather Wool Silk Proteinaceous (from
  animals)

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Field Testing

• Even a simple IST (ignition susceptibility test)
  has a pedigree NFPA 705 Field Flame Tests for
  Textiles and Films Recommended Practice 1997
• Small flame (lighter or match) held to bottom
  edge or corner of small sample held vertically in
  air.
• Observe flame color and behavior
• Observe smoke color and production odor
• Blow out and observe smolder (if any)
• Test ash texture

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Fire Investigations and the Forensic Lab

• WHY?
• Because the investigator will be expected to
  justify his or her conclusions about ignition,
  flame spread, and size of the fire on that data.
• Cigarettes will not ignite most synthetics but
  will ignite most cellulosic materials.
• Open flames will quickly ignite most synthetics
  or blends, but then what will the fabric do?
• Self-heating processes do not result in ignition
  of thermoplastic substrates.

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CRIMINALISTICS
Purpose Not Just for Identifying Things! Aid
in Reconstructing Events and Human Activities
Link suspect and scene or victim and suspect

• Debris containing suspected volatiles
• Liquids
• Charred or burned paper documents
• Clothing and shoes
• Tools and tool marks

• Blood stain patterns
• DNA/saliva
• Glass fragments
• Paint chips
• Hairs and fibers
• Firearms

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Criminalistics (Non-Fire) Evidence

• Investigators must be aware of proper collection
  and preservation methods for each type of
  evidence
• The lab needs to get involved in training!
• Chain of custody traces an item of evidence from
  its discovery to court.
• Spoliation is the destruction or alteration of
  evidence.
• ASTM E 860 establishes practices for examining
  and testing of evidence which may be involved in
  criminal or civil litigation.

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Other Relevant ASTM Guidelines

• ASTM E620 Practice for Reporting Opinions of
  Technical Experts
• ASTM E678 Practice for Evaluation of Technical
  Data
• ASTM E1188 Standard Practice for Collection and
  Preservation of Information and Physical Items by
  a Technical Investigator
• ASTM E1459 Standard Guide for Physical Evidence
  Labeling and Related Documentation
• ASTM E1492 Receiving, Documenting, Storing and
  Retrieving Forensic Evidence

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Fire Investigations and the Forensic Lab

• Flash Point?
• Melting Point (or Softening Point)?
• Does this material burn by smoldering, flaming,
  or both?
• Ignition Conditions vapor pressure,
  autoignition temperatures, conditions?
• What would be the effect of enhanced oxygen or
  reduced oxygen concentrations?

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Fire Investigations and the Forensic Lab

• What Is That Mess?
• What Was It and How Did It Get That Way
• Physical exam
• UV/ALS
• X-rays
• Elemental analysis
• SEM
• Broken by mechanical
• force, shock, or heat?
• Exemplars?

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Fire Investigations and the Forensic Lab

• Clothing items
• Impact or transfer patterns - actions
• Thermal scorching, melting, charring, color
  changes position and posture of wearer
• Bloodstains presence, patterns, toxicology
• Thermal properties conductive or transparent to
  infrared related to burns or protect areas on
  body

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Fire Investigations and the Forensic Lab

• Shoe, tire, or tool impressions
• Latent fingerprints
• Body fluids - DNA

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Fire Investigations and the Forensic Lab

• What can the broken glass and bloodstains on this
  door tell the criminalist?
• DNA alone doesnt tell the whole story!

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Fire Investigations and the Forensic Lab

• Recognition of trace evidence glass, fibers,
  paint, soil - and toolmark evidence and their
  forensic significance.
• Who else can or should do it?

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Fire Investigations and the Forensic Lab

• Glass
• Thermal or mechanical break?
• Type?
• Match to Source?
• Reconstruction?

DNA on the mouth of the bottle!
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Fire Investigations and the Forensic Lab

• New Innovations Need to be Properly Tested.
• Sniffers
• Absorbent materials
• Containers
• UV and ALS detection of accelerants
• CANINES
• GC/MS/MS

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Keeping Up with the Dogs

• In the late 1980s canine accelerant detection
  teams were introduced.
• Their sensitivity to odors was quickly proven
  superior to lab methods.
• Conflicts grew when handlers insisted that a
  canine alert was proof of the presence of an
  ignitable liquid even when the lab results were
  negative.

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Keeping Up with the Dogs

• Analysts were forced to improve the sensitivity
  of lab methods to the ppb levels of the canines.
• Then we discovered that there were many products
  (carpet, clothing, shoes, copy paper, etc.) that
  contained traces of solvents from their
  manufacture.
• The issue was not of sensitivity but of the
  selectivity needed to discriminate between
  innocuous contaminants and significant residues
  of real accelerants.
• GC/MS is the only defensible technique.

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Fire Investigations and the Forensic Lab

• Now that we can be as sensitive as the dogs, the
  question became Is There Such a Thing as Too
  Sensitive?
• What Do We Know About the Substrate and Its
  Possible Background Contributions?
• What control or comparison samples exist?
• Can Old residues be significant?

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Fire Investigations and the Forensic Lab
This fire in Pennsylvania killed two elderly
people. An adult son escaped and was charged with
their murder based on burn patterns in the room
of origin and the presence of traces of highly
evaporated gasoline in the wood floor (but not in
the carpet or pad).
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Fire Investigations and the Forensic Lab

• New petroleum products and new uses for
  not-so-new products have added to the difficulty
  of interpreting GC results
• GC/MS almost mandatory today
• Aware of contributions of fuels involved
• Comparison samples essential
• Substrates AND products
• Pyrolysis products in both oxygenated and oxygen
  deprived conditions

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Fire Investigations and the Forensic Lab

• We cannot come to correct conclusions without
  context.
• We cannot deliver valuable analyses by rote
  methods (unlike drugs, blood alcohol or even
  DNA).
• We owe it to our clients to offer the best array
  of services
• Many of the reliable and useful techniques are so
  rarely used that no ASTM technique exists BUT
• That does not mean we should not offer them as
  long as they are based on good science!

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Thank you!
WE must prepare criminalists with the broad
scientific knowledge AND the reasoning capacity
to evaluate real evidentiary problems and
properly select, use, and defend the procedures
used to solve those problems.

• John D. DeHaan, Ph.D., F-ABC, CFI, FFSSoc
• Fire-Ex Forensics, Inc.
• 3505 Sonoma Blvd 20-314
• Vallejo CA 94590
• 707 643-4672
• 707-643-4682 (Fax)
• jddehaan_at_fire-exforensics.com