1. Forensic Hair Analysis

2. Hair and Crime Locard’s Exchange Principle
Most common type of Trace Evidence: materials that are generally small in size and can be easily transferred when physical contact occurs between people and/or objects
Scenarios involving hair evidence: homicide, sexual assault, aggravated assault, hit-and-run incidents

3. Hair Evidence Composed of mostly protein keratin
Outgrowths of skin of mammals
Each species has characteristic hair
Length, color, shape, root appearance, hair anatomy
Variability also exists from body part to body part
Head, arms, legs, pubic, armpits, face

4. What makes hair good evidence?
Resistance to chemical decompostition
Ability to retain structural features over long period of time
Can get DNA from root

5. Hair Microscopy Used to determine human vs. animal Specify race
Part of body
Fell out naturally? Removed by force?
Person on drugs? Have disease?
Specify if hair was dyed
Cut with scissors, razor, or burned

6. Hair Characteristics

7. Hair Characteristics

8. Parts of a Hair
Cuticle
Cortex
Medulla

9. The Cuticle Formed by overlapping scales
Always point to the tip end of each hair
Scales form from keratinized, flat cells that come from follicle
Scale pattern cannot individualize human hair
Used for species determination
Use nail polish casting to see scale pattern

10. Pics of the cuticle Coronal scales Found in small rodents, bats
Rarely in humans

11. More on the cuticle
Spinous scales
Found in mink, seals, cats

12. Human cuticle pattern Imbricated or flattened
Found on humans and many animals

13. Medulla Core of hair Not always present or present in only parts
Medulla of human hair varies
Also depends on body region
Head – often missing or narrow
pubic – often wide & continuous
Limb – discontinuous & granular
Beard – double medullas
Animals have specific pattern

14. Common medulla shapes In humans, you will usually see… Absent
Trace (fragmented)
Discontinuous (interrupted)
Continuous

15. Human Medullas

16. Medulla - animal Uniserial ladder medulla – rabbit
Multiserial ladder medulla - rabbit

17. Medulla - animal
Lattice – deer
Thick, continuous = dog

18. Other animal medulla
Cat –
Seal -

19. Cortex Main body of hair Contains pigment granules Determine color
Mostly found in root, but may be founds throughout length of human hair
Determine color
Also use thickness to determine match

20. Root and Hair Growth
3 Developmental Stages
Anagen
Catagen
Telogen

21. Anagen Growth
Initial growth stage in which the hair follicle actively produces hair
Longest – can last between 2-6 years
Hair grows and dead, keratinized cells are pushed through the scalp
Root is attached to follicle

22. Catagen Transitional Phase Hair stops growing
1-2 weeks
Hair stops growing
Root has club-like appearance

23. Telogen Lasts approximately 3 months
Once follicle stops producing keratin, hair naturally sheds
At any one time, about 10-18% of head hairs are in the telogen
Follicle is hard, white lump

24. Animal vs. Human hairs
Human hair – consistent color, animal can change radically across hair
Medulla occupies much larger space (> 1/3 diameter) in animals
Scale patterns
Wide variability among animal hairs
Coarse outer hairs (guard hairs)
Fine fur hairs
Tactile hairs (whiskers)
Tail hairs
Mane hairs

25. Collecting Hair Evidence: 6 Main Methods
Observable hairs collected with tweezers
However, tweezers can damage hair structure or break root where DNA exists
Infrared or laser sources can make hairs more visible
Clear tape lifts visible and nonvisible hairs off a variety of surfaces
Each piece of tape labeled for source

26. More ways to collect hair
For larger crime scenes, vacuuming may be used
Also good for stationary objects that cannot be transported
Brushing, scraping, or shaking garment over large sheet of white paper
Garment bagged and agitated
Combing – used to detect cross transfer of hairs

27. FAQ 1: Can age/sex of an individual be determined by a hair?
Age cannot be determined except with infant hair (very fine)
Sometimes dye/bleaching offers a guess to sex
Nuclear DNA will tell male/female

28. FAQ 2: Can you tell if the hair was forcibly removed?
Hair root w/ follicular tissue (root sheath cells) adhering to it
Pulling or forcibly combing/brushing
Hair naturally falling off has bulbous-shaped root free of tissue

29. FAQ 3: How can you individualize human hair?
Look at the nuclear DNA in hair root or on surrounding tissue (preferable)
When no follicular tissue present, mitochondrial DNA (passed from only mother to child) from root cells
Much more available than nuclear
Nucl. DNA can narrow to 1 in one billion; mitochondrial cannot individ.