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Forensic Analysis of Hair

Hair in Forensics . It is important to note that it is impossible for experts to individualize a hair (in other words, match it perfectly to any single head/body)Hair samples can be used to place an individual at a location by comparing hair recovered from the crime scene with control samples . Hair Morphology .

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Forensic Analysis of Hair

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    1. Forensic Analysis of Hair Alex Picariello SBF6-02 Instructor: Mary Villani

    3. Hair Morphology Hairs grow from hair follicles The bulb (root) of the hair is contained within the follicle The shaft of the hair connects with the root The shaft has three parts: the cuticle, the cortex, and the medulla The shaft ends with the tip of the hair

    4. The Cuticle Outside layer of the hair Allows the hair to retain structural features and resist chemical decomposition Formed by layered scales (hardened and flattened specialized cells that come from the follicle)

    5. The Cuticle (Continued) Scale pattern is useful for species identification of hair samples Observing the scale pattern is done by creating a cast (embed the hair in a softened vinyl or nail polish and then remove it once the medium hardens)

    6. The Cortex Layer underneath the cuticle Composed of spindle-shaped cells that run parallel to the hair Contains the pigment granules that give hair its color (distribution, color, and shape of these granules help with comparing hair samples)

    7. The Medulla Appears to be a “central canal” running the length of the hair Medullary Index: The fractional value that demonstrates the diameter of the medulla in relation to the diameter of the entire hair shaft (animals have an MI of 1/2 or greater, humans 1/3 or less) The shape of the medulla changes from animal to animal (humans have cylindrical medullae, if they are present at all, whereas cats have scaly-looking medullae)

    8. The Medulla (Continued) Medullae can appear in three forms: fragmented, continuous, interrupted, or absent The three forms vary from person to person, and even from hair to hair on a single individual

    9. Hair Roots The hair root allows for the growth of the hair There are three phases of root development: Anagen, Catagen, and Telogen Each root phase has a different shape and size

    10. Root Development

    11. Anagen Phase Can last up to 6 years, during which time hair growth occurs The root is connected to the follicle and looks like a flame Forcibly removed roots in the Anagen phase may have a piece of DNA attached known as a follicular tag (useful for individualization)

    12. Catagen Phase Can last 2-3 weeks, hairs grows at a slower rate Elongated appearance as the root is gradually being forced out of the hair follicle

    13. Telogen Phase Can last 2-6 months, during which time hair growth has completely stopped Hair is eventually forced out of the follicle and shed naturally

    14. Hair Identification It is important for forensic experts to be able to figure out to which species a particular hair sample belongs (this can be done by looking at the scale formation of the cuticle and the medullary index) The most important characteristics of hair are scale structure, medullary index, and medullary shape Forensic experts are often requested to match crime scene hairs with hairs removed from a suspect

    15. Hair Identification

    16. Hair Comparison Criminalists attempt to match the color, length, and diameter of the hair Presence of medullae, and the pigment granules’ shape, size, and distribution are important comparable characteristics

    17. Determining Body Area

    18. Determining Race Negroid Hair Kinky Dense, unevenly-distributed pigments Flat to oval cross-section Caucasoid Hair Straight or wavy Fine to coarse, evenly-distributed pigments Oval to round cross-section

    19. Race Hairs

    20. Determining Forced Removal Hair that fall naturally from the body will have a bulbous root Hairs that have root sheath cells (the follicular tissue) attached are more likely to have been forcibly removed

    21. Individualizing Hair Forensic experts can use the DNA found in the root or in the follicular tissue attached to the root for individualization The follicular tag is the best source of DNA DNA is best found in the Anagen and Catagen phases

    22. Collecting Hair Samples When collecting control samples from suspects, it is important to obtain hairs from the same part of the body that the crime scene hairs came from The entire length of the hair should be collected because a hair can vary morphologically over its entire length Control samples must contain a large quantity of hair (roughly 50 hairs) from that particular body area, because individual hairs can vary on a single person

    23. Collection

    24. References http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric1.htm#Hair%20Evidence http://www.crimeandclues.com/hair_evidence.htm http://www.crimelibrary.com/criminal_mind/forensics/trace/5.html http://www.dermatology.org.uk/portal/activities/images/hair-follicle-parts.jpg http://thebeautybrains.com/wp-content/uploads/2006/10/damagedhairshaft.jpg

    25. References (Continued) http://www.top-hair-loss-remedy.com/images/hair-cross-section.gif http://hairmedulla.com/assets/img/HairMedulla.jpg http://www.fbi.gov/hq/lab/fsc/backissu/july2004/images/2004_03/figure22.jpg http://www.dermatology.org.my/hairloss/images/hairloss/catagen.jpg

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