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Chapter 15
Forensic Aspects of Fire Investigation
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.2
Introduction Complex and difficult:-planned-not present-destruction is extensive
Criminalist’s function:-detecting/identifying-relevant chemical materials
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.3
Arson Facts
Second leading cause of death by fire (US)
#1 cause of property damage (fires)
>500 killed in 1996
> property damage $2 billion.
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.4
Arson Facts
1996:-63%= under 20 years old-35%= under 15 years old >90 percent of all arson deaths occur
in homes Growing link between arson and drugs -20% - 25% cases are drug-related.
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.5
The Chemistry of Fire Oxidation-oxygen + other substances=new
substances
Ignition temperature:-minimum temperature-spontaneously ignite fuel
Combustion:-heat evolved when a substance burns
Rate/speed of oxidation reaction
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.6
The Chemistry of Fire Liquids:-flash point Solids:-pyrolysis Glowing/combustion/smoldering:-burning at fuel-air interface Spontaneous combustion:-rare-heat-producing process-poorly ventilated containers/areas
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.7
Chemistry of fire
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.8
Heat Transfer
Conduction:-movement of heat through solid objects Radiation:-transfer of heat energy by electromagnetic
radiation Convection:-transfer of heat energy by the movement of
molecules within a liquid/gas.
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.9
ARSON FIRES
Covert:-hide arson
Overt:-send message
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.10
ARSONISTS
Profit: (torch)
Pleasure: (spark)
Anger: (murderer)
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.11
The Fire Scene Majority of arson fires:-petroleum-based accelerants
Walk through of scene:-locate point of origin-locate anything suspicious -no warrant needed at this point-ignitors such as matches, an electrical
sparking device, or parts of a “Molotov cocktail” must also be conducted.
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.12
ARSON-separate/unconnected fires-“streamers” -severe burning on floor
Fires burn up/out-point of origin-lowest point-showing intense characteristics
Combustible liquids rarely entirely consumed
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.13
Up and out
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.14
Burn patterns
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.15
Collection of Fire Evidence Point of origin:-ash/soot-porous materials -airtight containers Traces of flammable residues located:-vapor detector/sniffer-dog Sampling:-similar/uncontaminated control specimens-”substrate control”
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.16
Awwww. Isn’t he cute?
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.17
Analysis of Flammable Residues
Heat:-airtight container-volatile residue -driven off -trapped in airspace-vapor (headspace) removed with syringe-injected into GC-separated into its components-recorded on the chromatogram
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.18
Gas Chromatography Most sensitive/reliable instrument:-detecting/characterizing residues-petroleum distillates-gasoline/kerosene GC:-separates hydrocarbon components-chromatographic pattern -particular product Comparison of GC peaks from scene debris to
known flammable liquids-identify accelerant used
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.19
Analysis of Flammable Residues
Vapor concentration technique:
- charcoal strip in the container heated-absorbs vapors-washed with solvent-recover vapors-solvent injected into GC
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.20
GC/MS of Flammable Residues Complex patterns:
-simplified-passing separated components -GC column -through mass spectrometer-component fragmented into collection of
ions-analyst identified peaks associated with
ions of a particular accelerant
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.21
Burn pattern
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.22
Dirty work
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.23
Under a house
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.24
Can you locate point of origin?
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.25
Obvious point of origin
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.26
Indicates accelerants. Fire burns up even when a wall collapses the floor underneath it doe not burn down like here.
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.27
Pour pattern
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.28
Pour pattern on wood floor. The accelerant is burned away leaving the floor undamaged.
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.29
Pour pattern
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.30
Not a smart BBQ technique
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.31
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.32
Some scenes are large
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.33
Burn pattern
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.34
Oh yeah Sherlock. You certainly hid that pour pattern well