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Chapter 13
Trace Evidence II: Paint, Glass, and Soil
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Paint Most common:
-automobile paint finishes
-multiple coatings
-electrocoat primer/primer surfacer/basecoat/clearcoat.
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Methods for Paint Comparison Diversity:
-forensic significance-questioned and known specimens-stereoscopic microscope: color/surface texture/color layer sequence-pyrolysis gas chromatography/infrared
spectrophotometry: paint binder formulations
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Methods for Paint Comparison Solid:-heated (pryolyzed)-decompose into gases-GC column -small amounts of paint-ID make/model of car-PDQ data base
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Paint Comparison
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Microscopic comparison
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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The Lab
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Trace
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Collection and Preservation Paint chips:
-persons or objects-hit-and-run incidents.-paper druggist folds/vials -garments/objects smeared -standard/reference -tools
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Glass Fragments Amorphous substance:
-silicon oxides-metal oxides-random atoms-tempered glass-laminated glass
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Glass Fragments Problem:-association -minimizing/eliminating sources Comparison:-density -refractive index
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Flotation Method Glass densities:
-immersed in liquid-density adjusted by-chip remains suspended -same density as liquid -compared to other glass-suspended/sink/float
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Immersion Method Refractive index:
-glass particle in a liquid -refractive index is varied-equal to particle-match point-Becke line: bright halo near the border of
particle -Becke Line disappears
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Analyzing Cracks radial fractures
concentric fractures
-direction of impact.
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Radial fractures
Concentric fractures
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Looking at end of broken pane of glass
CONCENTRIC FRACTURES
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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End of broken piece of glassRADIAL FRACTURES
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Analyzing Cracks
Directionality:
High-velocity:-wider at the exit side -3 R rule:Radial cracks form a Right angle on
the Reverse side of the force-terminates at existing line of fractures
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Projectile hole
Formation of a bullet hole in a pane of glass. Note the crater form of the hole and the arrow shows the direction of the bullet.
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Collection of Glass Find all the pieces
On suspect
Representative known sample
solid containers
individually wrapped in paper
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Soil Value:
-prevalence at scenes-transferability-easily differentiated-side-by-side visual comparison: color texture different locations
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Removing evidence from sole of boot
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Foot wear impression compared to shoe
Tire wear impression compared to tire
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Removing shoe evidence
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Jaw bone in the dirt-nightmare for trace evidence/contamination
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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It’s hard to get ahead.
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Homeless camp in the desert with multiple victims
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Does crime scene processing still seem as glamorous as CSI?
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Comparison of Soil Forensic geologists:
- Compare mineral content-vast variety of minerals/rocks -artificial debris -points of comparison
Forensic ScienceRichard Saferstein
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Collection of Soil Standard /reference:-various intervals-100-yard radius -site of the crime
on suspect:-shoe/garments-must not be removed -wrap individually in paper-lab