Trace Evidence Flashcards
Trace vs transfer evidence
Trace evidence is not always noticeable; transfer is the result of contact
Evidence can be searched for hairs using what?
A stereomicroscope
Picking
Observing and removing individual hairs
Taping
Using the adhesive side of tape to pick up hairs
Vacuuming
Using a suction device with a fine screen to capture hairs
Known hair samples are collected by
Combing and pulling
Hair
Filament growth from the skin
Comprised of keratin, proteins, amino acids and melanin
Cuticle
Outermost later of the hair shaft
Cortex
Second layer of the hair shaft
Medulla
Core of the hair shaft
Anagen phase
Active growth phase of hair
Catagen phase
Hair stops growing
Telogen phase
Hair is naturally shed
Protein fibers
Composed of polymers and amino acids; wool and silk
Cellulosic fibers
Formed from glucose; cotton and linen
Mineral fibers
Composed of silica; asbestos
Natural fibers
Protein, cellulosic, mineral
Manufactured fibers
Synthetic, Inorganic, Regenerated
Raman Spectroscopy
Measures vibrations that bonds undergo within molecules
How should paint evidence be collected?
Either by collecting the entire item with paint or removing the paint from the item
Organic coatings of paint
Electrocoat, primer, basecoat, clearcoat
Electrocoat
First layer; color ranges from black to grey
Primer surface
Second layer; lots of color pigment
Basecoat
Becomes the visual color of the automobile
Methods of chemical analysis of paint
FTIR and pyrolysis gas chromatography
FTIR
identifies paint materials through measuring absorption of infrared radiation
Major types of glass
Flat, container, fibers
Types of cracks
Radial
Concentric
Intersecting
Radial cracks
Start at the area of impact and move outwards
Concentric cracks
Occur on side of glass where force was applied; looks like a circle around impact zone
Wallner lines
Arc-shaped marks that help determine which side of the glass force was applied on
Becke line
Bright halo at the edge of an object
Match point in glass
Line disappears
Cortical Fusi
Small air pockets trapped within the hair body
Follicular tag
Tissue and living cells forming the proximal tip of a hair strand
Human hair has a ____ cuticle
imbricate
Human hair has a ____ medulla
unstructured
Human hair cortex makes up _____ of the width
65%
Hairs in which growth stage are most desirable to be collected at a crime scene?
Anagen because they have a follicular tag
The light microscope is good for ______
magnification
The right tool for anisotropy and birefrigence is the _____
polarizing light microscope
The peaks in UV and IR spectra are caused by
Different types of chemical bonds in the material
Sherwin Williams makes water-based latex paint in a number of different finishes (levels of shininess) matte, satin, semi-gloss, and glossy. If you compare two paints of the same color, but different finishes, which paint component will be chemically different?
the modifier
Both Layer comparison and physical match can be performed with which type(s) of paint evidence
chips
I knocked over a shelf and broke a clear glass unicorn and a clear glass mason jar. Both have nearly identical density, so I will need to use their refractive indices to determin which bits of glass go with which item
Polarizing Light Microscope
Hot stage refractometer
Becké line analysis
When using the hot oil method, what do we compare between our suspect and our known?
The temperature at which the outline of the glass disappears.
