Trace Evidence Part II

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Trace EvidencePart II
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Summary

• Microscopic Analysis
• Types of Trace Evidence

• Glass
• Hair (fur)
• Fibers

• Paint
• Soil
• Gunshot Residue

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Hair

• What is hair?
• What crimes are hair involved in?
• How is hair collected?
• How is hair analyzed in the lab?

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Trace gt Hair

• What is hair?

• Natural fibers of animal origin
• Terms human hair animal fur
• Usually growing (live root)

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Trace gt Hair

• What is hair?

• Cellular material in the hair shaft (mtDNA)
• Good DNA in the hair root for forcibly removed
  hairs (STR)

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Trace gt Hair

• What crimes are hairs involved in?

• Hairs are shed from people can link a person to
  a crime scene.
• Animal fur may also link a person to a crime
  scene.

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Trace gt Hair

• How is hair collected?

• Visually by hand or with forceps.
• Possibly tape lift.
• Packaged in sealed containers.

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Trace gt Hair

• How is hair analyzed?

Look at class characteristics (microscope)

• Color

• Medulla, Cortex, Cuticle

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Trace gt Hair

• How is hair analyzed?

Medulla

• Line down middle of hair

• Species ID or human ID

• Present, absent, or fragmented

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Trace gt Hair

• How is hair analyzed?

Cortex

• Color of hair
• Species ID or human ID
• May contain pigment blotches
• May contain air pockets

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Trace gt Hair

• How is hair analyzed?

Cortex

• Humans 1 color entire length
• Animals color can vary at root/middle/tip

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Trace gt Hair

• How is hair analyzed?

Cuticle

• Scales on outside of hair
• Species ID only
• Humans imbricate

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Trace gt Hair

• How is hair analyzed? (cuticle)

Procedure

• Put clear nail polish on slide.
• Place hair in nail polish wait to harden.
• Remove hair look at indentations in nail polish
  (microscope).

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Fibers

• Fibers are very useful as trace evidence

• Vary widely in class characteristics
• color, shape, chemical composition, etc.
• Easily transferred from one source to another
  (carpets, clothes, etc.)
• Significant persistence (wont degrade)

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Trace gt Fibers

• How are fibers used as evidence?

• As with other trace evidence, fibers can be
  transferred to/from a person or objects linking
  them to one another.

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Trace gt Fibers

• How long do fibers persist?

Most fiber evidence is lost (fall off) a short
time after the transfer occurs.
The fibers that do remain will be persistent.
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Trace gt Fibers

• Fibers can be classified into three main
  categories

• Natural (animal, plant, mineral)
• Manufactured
• Synthetic

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Trace gt Fibers gt Natural

• Natural Fibers

• Found in nature
• Can be artificially colored or treated

Cotton
Wool
Hemp
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Trace gt Fibers gt Natural

• Animal Fibers

• Wool - Hairs from sheep
• Most common of animal fibers
• Hairs are spun to form thread

• Silk - comes from silkworm
• Spun as double filament (separated before use)
• Because of length, doesnt shed easily

Other Hairs from Animals
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Trace gt Fibers gt Natural

• Plant Fibers

• Cotton - seed hairs of cotton plant
• by far most common fiber (find almost everywhere)

Under microscope, fibers resemble twisted ribbon
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Trace gt Fibers gt Natural

• Other Plant Fibers

Linen - stem fiber from flax plant Kapok - from
seed hairs of kapok plant Other fibers - Manila,
hemp, sisal, jute
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Trace gt Fibers gt Natural

• Mineral Fibers

• Asbestos - crystalline material
• Used to be used for insulation
• Fractures into thin rods that can get into your
  lungs can kill you
• Not used much anymore

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Trace gt Fibers

• Filament vs. Staple

Filament Long continuous fiber (like silk)
Staple Filament is cut into smaller pieces
staples are spun together to form thread (like
cotton)
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Trace gt Fibers gt Manufactured

• Manufactured Fibers

Regenerated Fibers

• Cellulose is dissolved, then resolidified to form
  the polymer fiber
• Can occur in filament or staple form

Example Rayon
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Trace gt Fibers gt Synthetic

• Synthetic Fibers

• Man made
• Can also be filament or staple

Examples Nylon and Polyester
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Trace gt Fibers gt Synthetic

• Synthetic Fibers

• Acrylics
• More common as evidence
• Usually in staple form
• Staples spun together, similar to wool

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Trace gt Fibers gt Analysis

• Begin by identifying and comparing class
  characteristics for unknown sample (evidence) and
  known sample.

Known
Unknown
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Trace gt Fibers gt Analysis
Fibers from rug in a van.
Fibers found on victim.
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Trace gt Fibers gt Analysis

• Class characteristics

Color microscopic examination Size length
and width can be measured Shape cross section
is viewed
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Trace gt Fibers gt Analysis
Class characteristics

• Refractive Index n. The ratio of the speed of
  light in air or in a vacuum to the speed of light
  in another medium.
• Other microscopic properties (PLM)

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Trace gt Fibers gt Analysis
Class characteristics

• Chemical Composition determined by advanced
  instrumentation

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Trace gt Fibers gt Cordage

• Threads, Yarn, Rope, Cordage

Smallest component is fibers (staple) twisted
together to form thread or is a filament.
This thread can then be twisted with other
threads to form a thicker thread (string, etc.)
This thicker cord can then be twisted with other
thicker cords, etc.
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Trace gt Fibers gt Cordage

• Threads, Yarn, Rope, Cordage

Small cords or fibers twisted together to form
larger cords

• At each step, the number of cords can be counted.
  
• At each step, the twist direction is either S
  or Z

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Fiber niso nll n? Biref MP (ºC)
K1 1.518 to 1.528 1.544 to 1.551 1.505 to 1.516 0.035 to 0.039 Does not melt
K2 1.777 to 1.877 2.050 to 2.350 1.641 to 1.646 0.200 to 0.710 Does not melt
K3 1.512 to 1.521 1.510 to 1.520 1.512 to 1.525 -0.001 to -0.005 Does not melt
K4 1.538 to 1.539 1.530 to 1.539 1.538 to 1.539 -0.000 to -0.002 192 210
K5 1.533 to 1.545 1.568 to 1.583 1.515 to 1.526 0.049 to 0.061 210 230
K6 1.540 to 1.541 1.577 to 1.582 1.515 to 1.526 0.056 to 0.063 250 264
K7 1.522 1.553 1.507 0.046 182 186
K8 1.535 to 1.539 1.568 to 1.574 1.518 to 1.522 0.050 to 0.052 133 138
K9 1.567 to 1.575 1.632 to 1.642 1.534 to 1.542 0.098 to 0.102 282 290
K10 1.474 to 1.478 1.474 to 1.479 1.473 to 1.477 0.002 to 0.005 245 260
Q 1.520 1.515 1.513 -0.003 Does not melt
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Glass

• What is glass?
• What crimes are glass involved in?
• How is glass collected?
• How is glass analyzed in the lab?

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Trace gt Glass

• What is glass?

• Made from fused inorganic materials
• Amorphus not crystalline (molecules not
  arranged)
• Varies in elemental formula
• Many shapes and colors

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Trace gt Glass

• How is glass involved in crime?

• Small fragments can be used as trace evidence
  (link objects/people)
• Crime scene reconstruction

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Trace gt Glass

• How is glass collected?

• For reconstruction, detailed photographs can be
  taken or the entire pane of glass is collected.

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Trace gt Glass
How is glass collected?

• For trace evidence, usually visually collected
  with forceps and packaged in plastic bags.

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Trace gt Glass

• For reconstruction

Radial cracks
Concentric cracks
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Trace gt Glass

• For reconstruction

Concentric cracks
Radial cracks
Concentric cracks
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Trace gt Glass

• For reconstruction

1. Determine the direction of projectile.

• When looking at a radial section, conchoidal
  fractures point back to the origin of the break
• Core usually on opposite side of the origin

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Trace gt Glass

• For reconstruction

1. Determine the order of projectiles when
   dealing with more than one.

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1
3
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Trace gt Glass

• For reconstruction

1. Determine the order of projectiles when
   dealing with more than one.

2
1
3
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Trace gt Glass

• For trace analysis

Associate unknown glass found at the crime scene
with known samples to determine the source.

• Done with microscopic analysis
• Color, curve, thickness, etc.
• Refractive index Determined by placing glass in
  oils of different refractive indexes

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Trace gt Glass

• Refractive index

• Low relief no outside line R.I. of
  glass and oil are similar
• High relief thick outside line (Becke line)
  R.I. of glass and oil are different

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Paint

• What is paint?
• What crimes are paint involved in?
• How is paint collected?
• How is paint analyzed in the lab?

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Trace gt Paint

• What is paint?

• Colored chemical coating
• Covers cars and houses

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Trace gt Paint

• What is paint?

• Paint contains 3 things
• Vehicle binds components together
• Pigment gives paint color
• Extenders used to modify gloss, texture,
  opacity, etc.

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Trace gt Paint

• What crimes are paint involved in?

• Hit and Runs paint from car left at scene
• Other vehicular accidents
• Home invasion windows on suspect

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Trace gt Paint

• How is paint collected?

• Visually by hand or with forceps.
• Packaged in sealed containers.

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Trace gt Paint

• How is paint analyzed?

1. Possibly a physical match (jigsaw-like)
2. Associate the unknown paint with a known sample
   (class characteristics)

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Trace gt Paint gt Analysis

• How is paint analyzed?

Chemical composition determined by FT-IR
Chemical Fingerprint
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Trace gt Paint gt Analysis

• Paint can be in multiple layers

Each layer is analyzed to determine its physical
and chemical properties.
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Soil

• What is soil?
• What crimes involve soil?
• How is soil collected?
• How is soil analyzed in the lab?

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Trace gt Soil

• What is soil?

• Mixture of animal and vegetable materials, and
  minerals

• In many ways, soil has a unique composition in a
  given area.

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Trace gt Soil

• What crimes involve soil?

Due to the widespread location of soil (earth),
it can be used to associate people, objects, and
scenes in numerous cases.
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Trace gt Soil

• How is soil collected analyzed?

Collected in jars or vials.
Materials in soil are identified and quantified.

• Analysis relies on soil composition being
• Consistent over time in one location
• Different in different locations

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Gun Shot Residue (GSR)

• What is gun shot residue (GSR)?
• What crimes are GSR involved in?
• How is GSR collected?
• How is GSR analyzed in the lab?

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Trace gt Gun Shot Residue

• What is GSR?

Mixture of materials that originate from the
firing of a gun.
From the chamber
From the barrel
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Trace gt Gun Shot Residue

• What is GSR?

GSR will fall onto hands of person firing the gun.
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Trace gt Gun Shot Residue

• What crime is GSR involved in?

Crimes with guns
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Trace gt Gun Shot Residue

• How is GSR collected analyzed?

Hand/glove/paw is swabbed
Analysis

• Elements barium and antimony are found in high
  levels.
• Use powerful microscopy (SEM)
• Use chemical tests (color change reactions)