Transcript Chapter 15-Soil Glass Paint

Chapter 15Soil and Glass Analysis
and Paint too!
What is Soil?
Soil Material
• Partly Organic
– Decaying matter
– Ex. Peat: 100% Organic
• Partly Inorganic
– Minerals
– Ex. Sand: 100% Inorganic
What’s in soil?
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Rocks
Minerals
Vegetation
Animal Waste
Glass
Construction
Debris
• Asphalt
How Do Soils Differ?
• Color
How Do Soils Differ?
– 1,000 different colors
Wet soils appear dark!
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Texture
Particle size
pH
Density
Fossil types (Diatoms)
Mineral and Rock Content
Pesticides/Herbicides?
Forensic Geology:Geo-Tracking
Forensic Geology: Geo-Tracking
Forensic Geology: Geo-Tracking
Minerals and Rocks?
Minerals
=Naturally occurring crystals (2,200 known)
Look at: Color, shape, density, refractive index
Minerals
• Fluorescence
Rocks
= Contain a combination of different minerals
Soil and Crime
• Hit and Run: - Under-fender dirt/soil deposited
at impact with the victim. matching the grease on
the victim with the grease under the car.
• Rape: - Soil on clothing of a suspected rapist
placed suspect at the crime scene.
• Murder: - Soil found on murder victims used to
determine the location of homicides, especially
when the murder occurs in one location and the
body is then moved.
• Assault: - Identifying the type of rocks used as
weapons led to the source of the rocks and helped
locate suspects.
Soil Evidence Collection
Keep soil in clumps if from car
Layers tell the history of the soil being
added to the car
Soil Evidence Collection
100 yds
Collect soil at crime
epicenter and at intervals
up to a 100 yard radius
from crime
1 or 2 tablespoons
of TOP SOIL
All soils packaged separately
Glass
• One of the oldest manufactured product
• Amorphous
Ingredients to make glass:
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Sand (mostly silica sand)
Soda (Na2CO3)-lowers melting point
Lime (CaO)-makes it water insoluble
Combination of metal oxides:
• Ex. Sodium, calcium, magnesium, aluminum
between 1,500 and 2,500 degrees Celsius
Glass Production Video
Tempered or Safety Glass
• Car glass
• Dicing and little splintering
• Stress glass by rapid heating and cooling
=annealing
• Glass also strong from lamination
– Thin piece of plastic between glass layers
Borosilicate glass
• Able to withstand high temperatures 1500 F
• Add boron oxides to mix
Bullet-Proof Glass
• http://www.youtube.com/watch?v=h5HM3y
8d0NA
Glass Fracture Analysis
Glass Fractures
• Crime Scene Reconstruction:
-Force and Direction of Impact
-Type of projectile (bullet or rock)
Concentric Fractures
Radial Fractures
Projectiles+Direction of Force
Exit side of
bullet is a
deep crater
3R Rule
=Radial cracks form a Right angle on the
Reverse side of force
Concentric fractures originate on the
force side of glass
Multiple Bullet Holes
A
B
Which Bullet Came First?
Bullet Holes
• Radial fractures caused by the
passage of a bullet will stop at any
pre-existing fracture
Mechanical Fit Analysis
• Physical Fit of Edges
• Look at Glass Ream
Patterns
Glass as Forensic Evidence
Glass fragments recovered from clothing
number & distribution are important
a piece of glass embedded in a shoe has low
probative value
many small fragments from a shirt or sweater can
be highly significant
Glass must be classified
window glass vs broken bottle glass
Individualization may be possible
Other Classification Methods
Microscopy
float glass is absolutely flat
wine glasses are slightly curved
bottles have microscopic defects from mold
Fluorescence
when excited by UV radiation, many glasses
exhibit fluorescence
caused by heavy metals (including tin)
Fluorescence
 Can differentiate
between float and
non-float window
glass
 Can differentiate
between different
samples of float glass
in some cases
(a) non-float glass or non-float side
(b) float side Sample #1
(c) float side Sample #2
Comparative Studies
FBI has a data base of from glass
manufacturers of densities and
refractive indexes
=Used for frequency of occurrence
issues
If R.I.=1.5290 then found in 1/2000 specimens
If R.I.=1.5180 then found in 22/2000 specimens
Problem!
• Most glass is uniform in its making and
show no individualistic traits!
Refractive Index
Trace Chemical Analysis of Glass
Properties of glass and soil
– Physical Properties; can be measured
without changing the substance, i.e.,
color, hardness, Refractive Index,
birefringence, density, melting point,
etc...
Chemical Properties; the way a substance
changes (reacts), i.e., combustion
Density Determination
D = m/V
Sink or float
Density Gradient Tubes
Volume Displacement Method
Refraction
 The bending that
occurs when a light
wave passes at an
angle from one
medium to another
(air to glass)
 bending occurs
because the velocity of
the wave decreases
Refractive Index Determination
•Becke Line=Bright Halo that
disappears when medium and
fragment have the same
refractive indexes
•Medium index can be varied by
adjusting temperature of stage
Birefringence (a.k.a.Double
Refraction)
• Refraction of light in 2 directions
• Sandwich between polarizing filters
Paint
• Where do we find painted surfaces?
Paint and Locard’s Principle
• Small pieces of paint are often unwittingly
transferred between objects during
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vehicle accidents,
burglaries,
robberies,
assaults,
homicides,
even from simple contact with freshly painted
surfaces during a crime.
Paint Composition
Paints are opaque coatings that are typically
made up of three components:
Pigment: very tiny particles of organic and
inorganic colored compounds that give the
paint its characteristic hue.
Binder: suspends the pigment particles
and helps to firmly fix them to the surface.
Solvent: such as water or an organic
liquid, provides a consistency suitable for
spreading the paint on the surface.
Paints vs. Dyes
• Dyes:
– usually a soluble compound that binds directly
to the material and does not require any
medium to bind the colored material to the
surface.
Proper collection and preservation of paint evidence
from an automobile suspected of being involved in
hit-and-run incident. Paint that is foreign to the
suspect automobile is observed.
Procedure
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Scrape the foreign paint as well as all underlying
layers of paint off the car’s surface using a clean knife
or scalpel. The scraping must clearly show the layer
structure of the paint.
Obtain a control paint sample from an adjacent
undamaged area of the car. Again, all layers must be
included.
Package each paint specimen separately in a proper
container. A druggist fold or a vial makes an excellent
container.
Label all specimen containers. Evidence collector’s
name or initials, the date, and the sampling location
are to be shown. All items collected are to be
described in the evidence collector’s field notes.
Paint As Evidence
• Individual Characteristics or Class
Characteristics?
Class unless……
Multilayered Paint Chip
Custom Finishes
Problem
• A single type of car paint can be on many
different models
• For a given color/type of paint, batches don’t
vary much in composition
• Binder chemical composition may vary very
slightly from batch to batch
What to do? What to do?
PDQ (Paint Data Query)
• Law enforcement
database of specific
paint formulas added
onto cars since 1974
Pigments and History
● Ochre is a mineral that has been sought and used
by humans even before homo sapiens came into
existence
● It has been used as:
Body paint
Artist paint
Sun blocker
Medicine (antiseptic and clotting agent)
Possible religious symbol for blood, life, etc
Pigments
~35,000 -10,000 ybp
Prehistoric Cave Paintings
Pigments Used
Homo Sapiens
Charcoal, lampblack (soot) C
Pyrolucite,
MnO
Hematite,
Fe2O3
Magnetite,
Fe3O4
Limonite,
Fe2O3 *H2O
There is good evidence that in
the cave paintings that many
of the colors were a mixture of
various pigments, and at some
sites there is evidence that
ochre was calcined (heated) to
get other colors
Pigments
Prehistoric Cave Paintings
Pigments
Mineral Pigments in Use from
Ancient thru Medieval Times
Hematite
Magnetite
Limonite
Goethite
Malachite
Azurite
Cinnabar
Chrysocola
Lapis Lazuli
Realgar
Orpiment
Cinnabar
Verdigris (copper acetate - Ancient Greek)
Van Dyke Brown (17th century peat extract)
Hans Van Meegeren
Traded fake paintings for genuine
artwork in the 1930s
Christ and the Disciples at Emmaus
Supposedly an undiscovered
masterpiece by Vermeer
Johannes Vermeer
Last Supper supposedly
by Vermeer
Technique
• Used a synthetic phenolformaldehyde
resin - known as Albertol or Ambertol dissolved in a spirit such as turpentine
and/or an essential (i.e., non-fatty) oil such
as oil of lilac or oil of lavender, which
would then be mixed with hand-ground
powder pigments.
• He heated the resin transforming its
chemical composition so that chemical
tests would show it is really not the
chemical it actually was
• He painted over low value17th century
paintings. He scraped away old painting
“Leveling Paint”
• Art Fraud analysis
• Art Forger
Pigments in Forensic Geology
● Because many of the
pigments are minerals
standard geological
techniques such as
microscopy, X-ray
diffraction, SEM analysis,
and optical spectroscopy
can be used to discriminate
them
 The organic vehicle or binders
can be discriminated by Gas
Chromatography – Mass
Spectrometry