1. Hair
Forensics

2. Hair is physical evidence
Forensic characteristics of hair:
Color
Structure
Morphology
It is not possible to individualize human hair

3. Structure of Hair Hair is an appendage of the skin
Hair grows out of the hair follicle organ
The hair extends from the root embedded in the follicle, continues into a shaft and terminates at the tip end
Follicle developed during fetal development, no new follicles formed after birth
Hair has protein – keratin (also found in nails)

5. Hair Identification Important features:
Cuticle scale structure
Medullary index
Medullary shape
Other features: color, length, diameter; distribution, shape, color intensity of pigments
Comparison microscope is an invaluable tool
Want to comb hair from a crime scene to hair from a suspect
Hair usually from scalp or pubic region at crime scenes
Evidential value of the comparison will depend on the degree of probability with which the examiner can associate the hair in question to a particular individual

6. Hair Shaft Used for most intense examination Composed of 3 layers
Cuticle
Cortex
Medulla

7. Cuticle Outside covering of the hair
Makes hair resistant to chemical decomposition and makes it able to retain structural features over time
Structure:
Overlapping scales that point towards the tip end of each hair
Different species have different scale patterns

8. Cuticle View the cuticle with a: Scanning electron microscope
Cast of the hair’s surface and view under a compound microscope

9. Cuticle – Scale Patterns
3 types of patterns
Coronal: small rodents and bats but rarely in human hairs
Spinous: mink, seals, cats, and are never found in humans
Imbricate: human hairs and many animal hairs

10. Cuticle – Scale Pattern
Rabbit

11. Cuticle – Scale Pattern
Deer

12. Cuticle – Scale Patterns
Human

13. Cuticle – Scale Patterns
Dog

14. Cuticle – Scale Patterns
Cat

15. Cuticle – Scale Patterns
Mouse

16. Medulla Looks like the central canal running through a hair
More than half of the hair’s diameter
Medullary index: measure of the diameter of the medulla relative to the diameter of the hair shaft (fraction)
Humans: usually less than 1/3
Most other animals: ½ or greater
Presence and appearance varies from individual to individual and even among the hairs of a given individual

17. Human Medullary Index
0.53 nm
1.59 nm

18. Medulla 4 ways to classify: Continuous Interrupted Fragmented Absent
Most animals, Some humans (Asians)
Interrupted
Most animals
Fragmented
Humans
Absent

19. Medulla
Shape
Cylindrical shape: humans & many animals
Various shapes for some animals
Searchable database for 35 common animal hairs encountered in forensic casework

20. Medulla - Patterns
Rabbit

21. Medulla - Patterns
Deer

22. Medulla - Patterns
Human

23. Medulla - Patterns
Dog

24. Medulla - Pattern
Cat

25. Medulla - Patterns
Mouse

26. Hair Identification - Race
1st: Distinguish between animal vs. human
2nd: Identify race
Asian: wider diameter than the hairs of the other racial groups, thicker cuticle, continuous and wide medulla, larger pigment granules
Head hairs best for id-ing race

27. Hair Identification - Race
African: largest pigment granules and are grouped in clumps of different sizes and shapes.
Caucasian: evenly distributed pigment granules.

28. Hair Identification – Body Area
Head: uniform diameter and usually a cut tip
Pubic hair: coarse and wiry, exhibit considerable diameter variation or buckling, often have a continuous to discontinuous medulla
Start 1A on Wed

29. Root Shows if hair was removed with force
By their microscopic appearance, human hair roots indicate how they were removed. When growing hairs
are pulled out by force, their roots have flesh still attached (lower two), but if they just fell out (top) after their
growth cycle was finished, they have a distinctive rounded appearance.

30. Can we tell if hair was dyed?
Yes!
Color will appear in cuticle and cortex
Bleach removes pigment
Estimate time since dyeing or bleaching:
Hair grows at approximately 1 cm per month
Repeated dyeing or bleaching results in several lines of demarcation. This would serve to further individualize a particular hair specimen.

31. Damaged Hair
Left: scissor cut hair; razor cut hair; broken hair; burned hair

32. Special Characteristics
Left top: lice egg case; dark band near root indicates it was shed after death; double medulla

33. Collection & Packaging
Collect at least 50 full length head hairs from all over the scalp
Collect at least 24 full length pubic hairs from all pubic areas
Method: Pull hair out of skin, clip near skin line, or vacuum up
Rape case: comb pubic area with a clean comb to remove all loose foreign hair present before victim is sampled