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Kristin Steede

on 22 January 2015

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Transcript of Intr

more information
Trace Evidence
Hairs, fibers, paint
Morphology of Hair
Steps of examination
the first step
more information
Medulla patterns
more information
A collection of cells that looks like a central canal running through the hair
In animals, this canal occupies more than half of the hair's diameter
In humans, less than one-third
The presence and appearance of the medulla varies.
continuous (most animals)
interrupted (most animals)
fragmented (some humans)
absent (most human hairs)
Introduction to Hair

trace evidence= transferred between individuals and objects
Often corroborates other evidence developed during an investigation
In most cases, physical evidence cannot by itself positively identify a suspect -----> narrows the origin of the evidence
Vacuuming, tape lifts, picking, combing, scraping
Hair is an appendage of the skin that grows from the hair follicle
formed during fetal development - none produced after
Hair is a very common piece of physical evidence, but it is not yet possible to individualize a human hair to any single head or body. (narrowed down)
Hair extends from its root in follicle to the shaft
The shaft: cuticle, cortex and medulla (subject to the most intense examination)

1. Microscopic view of the hair looking specifically at its color and structure (morphology)
Is there any DNA? If so, DNA extraction, isolation and characterization

the scale structure covering the exterior of the hair
The main body of the hair shaft
A cellular column running through the center of the hair
two features that make hair a good subject for establishing individual identity are its resistance to chemical decomposition and its ability to retain structural features over a long period of time
these features are attributed to the cuticle or outside covering the hair
the formation
Cuticle is formed by overlapping scales. the scales form from specialized cells that have hardened and flattened in progressing from the follicle.
There are different scale patterns depending on the type of hair.
the scales of most animal hair can be best described as looking like shingles on a roof
the variety of patterns formed by animal hair makes it an important feature for species identification
since the cuticle is the scale structure covering the exterior, we can examine the cuticle to determine more about the hair

this can be done by simply putting the hair under a microscope or casting its surface

casting: embedding the hair in clear nail polish and once the medium has hardened, the impression of the hair's cuticle is left
the main body of the shaft
contained within the protective layer of the cuticle
made up of spindle-shaped cortical cells aligned in a regular way
IMPORTANCE: the cortex is embedded with the pigment granules that give hair its color
the color, shape and distribution of these granules provide important points of comparison among other individuals

more specifics
Cuticle patterns
Medulla features
The shape= both humans and animals have a cylindrical appearance
Animals= patterned shape (string of pearls)
Humans= rarely show continuous medullation
The root

more information
The root and other surrounding cells within the hair follicle provide the tools to produce hair and continue its growth
The human head hair grows in three developmental stages and the shape and size of the hair root is determined by the growth phase it is in
the first phase
Anagen phase:
can last up to six years
root is attached to the follicle for continued growth, giving the root bulb a flame-shaped appearance
when pulled from root, some hairs in the anagen phase have a follicular tag (DNA)
the hair will continue to grow, but at a decreasing rate during the catagen phase
the second phase
hair can last anywhere from two to three weeks in this stage
roots typically take on an elongated appearance as the root bulb shrinks and is pushed out of the hair follicle
once hair growth ends, the telogen phase begins
the third phase
root takes on a club-shaped appearance
over two to six months, hair is pushed out of the follicle, causing the hair to be naturally shed
Identification and Comparison of Hair
pretty easy to distinguish animal hair to human hair
less easy to compare human hair of different individuals
comparison microscope
when trying to find a match, focus on color, length, diameter, medulla, distribution, color and shape of cortex
can distinguish between dyed and bleached hair (1cm/month)
need reference hairs
Common Questions

1. Can the body Area from which the hair originated be determined?
Yes, scalp hairs, public hairs all show different characteristics (more information coming)
2. Can the racial origin of the hair be determined?
Usually. Mostly between white and black hair types. Black hair types tend to have unevenly distributed pigments (more round) and whites tend to have more evenly distributed pigments (more flat)
3. Can the age and sex of an individual be determined from a hair sample?
Age of individual cannot be determined except with infant hair. Infant hair tends to have very fine pigment and is short.
Collection and Preservation of Hair Evidence
Full transcript