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Chapter 13: Hairs, Fibers, and Paint + Kim Freeland
Terms in this set (40)
Extends from the root embedded in the follicle.
Continues into the shaft, which has three layers- Cuticle, Cortex, Medulla
Responsible for the resistance to chemical composition. Has the ability to retain structural features.
Protective outer covering of the hair shaft.
Consists of overlapping scales that point towards the tip end of each hair.
Made up if spindle-shaped cortical cells aligned parallel to the length of each hair.
Embedded with pigment granules that give hair its color
Collection of cells that look like a central canal
How is the cuticle analyzed?
Or making an impression and analyzing under a compound microscope
How is the cortex analyzed?
Mounted to a liquid medium with a refractive index close to that of hair.
The amount of light reflected off the hair's surface is minimized, the amount of light penetrating the hair is optimized.
How is the medulla analyzed?
A database with 35 most common animal hairs encountered in forensic casework.
Understand which animal's hair based on scale patterns and medulla type.
Necessary for hair production and growth.
Great place to look for hair damage, can tell you how hair is removed.
What are the three phases of hair growth?
anagen, catagen, telogen
-The period of active hair growth.
-The brief transition period between the growth and resting phases of a hair follicle
-2 to 3 weeks
Resting phase. the final phase in the hair cycle that lasts until the fully grown hair is shed.
-2 to six months
What microscope is important in comparing hair?
What characteristics are forensic scientists looking for when comparing hair samples?
Gross Characteristics: color, length, diameter
Microscopic Characteristics: Medulla, pigmentation, cuticle
What happens when hair is forcibly removed? What is the significance?
When pulled from root, hair in anagen phase has a follicular tag.
Follicular tag is a rich source of DNA that can be used in DNA analysis.
How many hairs are needed for evaluation?
50 full-length hairs from all areas of scalp.
24 full-length pubic hairs
In what cases are fibers important?
In any case where they may have been a transfer between the suspect and the victim.
Derived from animal or pant sources
fibers derived from either natural or synthetic polymers
Using a microscope to investigate fibers:
color, diameter, surface of fiber, presence of delustering particles, cross-sectional shape
Visible light microspectrophotometer to investigate fibers:
Compare fibers through spectral patterns
Chromatographic separation of dye constituents to investigate fibers:
small strands of fibers are compared for dye content by extracting the dye off each layer with suitable solvent. Then spotting the dye solution onto a thin layer chromatography plate
What are infrared spectrophotometry and polarizing microscope useful for in fiber analysis?
Identifying generic classes of fibers
Examples of manufactured fibers
polyester, nylon, acrylic, rayon
Titanium Dioxide makes fiber more opaque and scatters light to reduce luster
What do you want to look at when analyzing fibers?
Cross section, fiber diameter, surface texture, color, fiber length, crimp
What makes up paint?
Pigments and additives suspended in the binder
What are the paint coats called on an automobile?
Electrocoat, primer surface, base coat, clear coat
First layer, consist of epoxy-based resins to provide corrosion resistance
epoxy-modified, used to smooth and hide imperfections, highly pigmented
Color and aesthetics of the finish
unpigmented, improve gloss durability and appearance
What should be compared among questioned and known specimens?
color, surface texture, and color layer sequence
What are pyrolysis gas chromatography and infrared spectrophotometry useful for in paint analysis?
Distinguishing the formulation of paint binders
What is the PDQ?
Paint Data Query, a paint database.
An analysis can obtain information on paints related to automobile make, model, and year.
The database contains paint layer colors, primer colors, and binder composition.
Light microscope is commonly used for...
Hair and fibers
Fourier-transform infrared spectroscopy (FT-IR) is commonly used for...
to confirm the fiber type for synthetic fibers and chemical analysis of paint layers
What is a forensic vacuum used for?
To find hairs or special qualities of someone clothing (i.e. beads, sparkles, etc.)
In a vehicle v. vehicle collision, how far away should the cop sweep the road?
20 feet on either side of the accident
Is hair a class or individual characteristic?
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