1. Criminalistics Chapter 8
Hairs, Fibers, and Paint
Criminalistics
Chapter 8

2. Hair A good indicator of individual identity
Resistant to chemical decomposition
Retains structural features over time
Hair is not an absolute indicator of identity but can be a good indicator of identity

3. Morphology of Hair
Appendage of the skin that grows out of a hair follicle
Begins at the hair root embedded in the follicle and extends outward into the shaft and ends at the tip
The hair shaft is most commonly tested by forensic scientists

4. The Hair Shaft: 4 Parts The cuticle: outside covering of hair
Covered in scales that point toward the tip
Scales are used in identification of the hair
Animal V. Human Hair
Coronal “Crown Shaped” Scales
Imbricate “Flattened” Scales
Spinous “Spiny” Scales

5. Cuticle Photographs
The cuticle is a translucent outer layer of the hair shaft consisting of scales that cover the shaft.
This photograph illustrates how the cuticular scales always point from the proximal or root end of the hair to the distal or tip end of the hair.

6. Cuticle Photographs
                   Spinous or petal-like scales are triangular in shape and protrude from the hair shaft. They are found at the proximal region of mink hairs and on the fur hairs of seals, cats, and some other animals. They are never found in human hairs.
Photomicrograph of the proximal scale pattern in mink hairs. The imbricate or flattened scales type consists of overlapping scales with narrow margins. They are commonly found in human hairs and many animal hairs.

7. The Hair Shaft: 4 Parts
The cortex: inside the protective layer of cuticle
Made of cells that are aligned parallel to the length of the hair
Pigment granules that provide color are found in the cortex

8. The Hair Shaft: 4 Parts The medulla: found in the center of the hair
Predominant feature of hair
Can be continuous, interrupted, or fragmented
Can be different shapes in cross-section and can be searched using a database

9. Medulla Examples
In human hairs, the medulla is generally amorphous in appearance, whereas in animal hairs, its structure is frequently very regular and well defined.
Photomicrograph of Uniserial Ladder Medulla
Photomicrograph of Multiserial Ladder Medulla
The above examples have a well-defined appearance and came from a rabbit.

10. Photomicrograph of Animal Hair with vacuolated medullae.
Medulla Examples
Photomicrograph of Animal Hair with vacuolated medullae.
Photomicrograph of Deer Medulla with lattice-shaped medulla.

11. Human Medulla Examples
When the medulla is present in human hairs, its structure can be described as—fragmentary or trace, discontinuous or broken, or continuous. This figure is a diagram depicting the three basic medullary types.
Discontinuous Medulla in Human Hair

12. Animal Versus Human Hairs
Hair Identification
Animal Versus Human Hairs
Human hairs are distinguishable from hairs of other mammals. Animal hairs are classified into the following three basic types.
Guard hairs that form the outer coat of an animal and provide protection Fur or wool hairs that form the inner coat of an animal and provide insulation Tactile hairs (whiskers) that are found on the head of animals provide sensory functions

13. Animal Versus Human Hairs
Hair Identification
Animal Versus Human Hairs
Human hairs are generally consistent in color and pigmentation throughout the length of the hair shaft, whereas animal hairs may exhibit radical color changes in a short distance, called banding.
The medulla, when present in human hairs, is amorphous in appearance, and the width is generally less than one-third the overall diameter of the hair shaft.
The medulla in animal hairs is normally continuous and structured and generally occupies an area of greater than one-third the overall diameter of the hair shaft.

14. The Hair Shaft: 4 Parts
The root: provides for growth of old and new hair
Three phases of hair growth:
Anagen (up to 6 yrs): root attached to follicle for continued growth; root bulb is flame-shaped
Catagen (2-3 weeks): slowed growth; root bulb has an elongated appearance
Telogen (2-6 months): hair growth ends and is shed; root bulb is club-shaped

15. Phases of Root Growth Flame-Shaped Root Elongated Root
Club-Shaped Root

16. Identification and Comparison of Hair
Most comparisons are human v. animal
Human-human comparisons are problematic
Variable morphological characteristics
Vary from person to person
Vary within a single individual

17. Hair Comparison Use a comparison microscope
Compare with standard/reference samples
Try to match color, length, and diameter
Can determine dyed or bleached hair from natural
Time since coloring can be determined because hair grows ~1cm per month

18. Hair Comparison
Pigment granules are small, dark, and solid structures that are granular in appearance. They vary in color, size, and distribution in a single hair. In humans, pigment granules are commonly distributed toward the cuticle as shown in Figure 1, except in red-haired individuals as in Figure 2. Animal hairs have the pigment granules commonly distributed toward the medulla, as shown in Figure 3.
Figure 1
Figure 2
Figure 3

19. Human Hair Identification
Human hair can be identified by racial origin, body area and other classifying techniques.
Key characteristics serve as racial indicators.
These indicators are generalities and apply primarily to head hairs.
The examiner may encounter hairs that cannot easily be associated with a particular racial model because of poorly defined characteristics, limited size, or inconsistent indicators. These hairs can be identified as apparent racial mixtures or as not classifiable.

20. Caucasian Hair Identification
Shaft diameter: moderate with minimal variation (mean diameter for human head hairs - 80um) Pigment granules: sparse to moderately dense with fairly even distribution Cross-sectional shape: oval
Photomicrograph of Caucasian Head Hair
Photomicrograph of Cross-section of Caucasian Hair

21. Negroid Hair Identification
Shaft diameter: moderate to fine with considerable variation Pigment granules: densely distributed (hair shaft may be opaque) and arranged in prominent clumps Shaft: prominent twist and curl Cross-sectional shape: flattened
Photomicrograph of Negroid Head Hair
Photomicrograph of Cross-section of Negroid Hair

22. Mongoloid Hair Identification
Shaft diameter: coarse and usually with little or no variation Pigment granules: densely distributed and often arranged in large patchy areas or streaks Medulla: prominent (often broad and continuous) Cuticle: thick Cross-sectional shape: round
Photomicrograph of Mongoloid Head Hair
Photomicrograph of Cross-section of Mongoloid Hair

23. Hair Comparison Highly subjective comparative test
DNA analysis of hair is a much more reliable testing technique

24. Individualizing Human Hair
Nuclear DNA Analysis:
DNA found in the nucleus of the cell
Must have follicular tag or root structure present to test

25. Individualizing Human Hair
Mitochondrial DNA Analysis:
DNA found in cellular material outside of the nucleus
Can be tested without follicle or root structure
More copies of mitochondrial DNA in cells

26. Collection and Preservation Of Hair Evidence
Must be submitted with an adequate sample of hair from the victim of a crime, those entering a crime scene, or a suspect
Hair samples must be obtained from the same parts of the body
Usually involve head or pubic hair

27. Collection and Preservation Of Hair Evidence
Head hair: approximately 50 full-length hairs needed
Pubic hair: approximately 25 hairs needed
In rape cases, area must be combed for hair transfer and then packaged in a separate envelope

28. Collection and Preservation Of Hair Evidence
Hair must be pulled out of the skin or by clipping it at the skin line
Hair is collected from the victims of suspicious deaths at autopsy

29. Fibers Comprise our fabrics and garments
Important evidence in incidences that involve personal contact
Homicides, assaults, & sexual offenses
Can also be transferred in hit-and-run cases

30. Problems with Fiber Analysis
Mass production of garments and fabrics has limited finding origin points
It is very unusual to identify fiber evidence with a high degree of certainty

31. Natural Fibers Derived in whole from animal or plant sources
Animal sources: sheep, goats, camels, llamas, alpacas, mink, rabbit, beaver, and muskrat
Plant sources: primary source Cotton
                           
Wool Fibers
                           
Cotton Fibers

32. Cross-Sectional Patterns of Man-Made Fibers
Derived from either natural or synthetic polymers
Most have distinguishable cross-sectional patterns
Examples: Rayon, Nylon, Acrylic, Polyester, and Spandex
                  
                  
Cross-Sectional Patterns of Man-Made Fibers 

33. Identification and Comparison of Man-Made Fibers
Microscopic comparison using a comparison microscope
Color and Diameter
Striations and Pitting
Shape of Fiber in Cross-Section

34. Identification and Comparison of Man-Made Fibers
Dye comparison using a microspectrophotometer
Not limited by size of sample

35. Identification and Comparison of Man-Made Fibers
Chromatography
Separate shades of color on a chromatograph

36. Identification and Comparison of Man-Made Fibers
Test chemical composition
Fibers are separated into classes
Light Analysis
Light passing through a fiber will be polarized and have a specific index of refraction
Refraction indexes can be compared

37. Problems with Fiber ID
Fiber strands cannot be linked with any certainty to any single garment or origin
Due to mass production of clothing, carpets, and other fiber sources

38. Importance of Fiber Evidence
Circumstances of the case
Other evidence that may link the suspect to the scene
Location, number, and nature of fibers examined
Judgment of the experienced examiner

39. Collection and Preservation of Fiber Evidence
Fiber evidence often cannot be seen with the naked eye
Fiber evidence can be associated with any type of crime and items must be packaged separately

40. Packaging of Fiber Evidence
Articles of clothing must be packaged separately in paper bags
Carpets, rugs, and bedding must be folded carefully to preserve fiber evidence
Car seats must be covered in plastic sheets
Knife blades should be covered to protect fibers that may be stuck to them

41. Packaging of Fiber Evidence
If fibers are to be removed from evidence before it goes to the lab:
The possibility exists that the evidence would be lost in moving it from the crime scene
Clean forceps must be used and the evidence double enveloped.

42. Paint Evidence Used in hit-and-run and burglary cases
Often two or more samples are examined to determine a common origin

43. Automobile Paint Layering
First Layer: Electrocoat Primer
Provides corrosion resistance to steel
Second Layer: Primer Surfacer
Hides any seams or imperfections in the automobile’s body
Third Layer: Basecoat
Color of the automobile
Fourth Layer: Clearcoat
Improves gloss, durability, and appearance

44. Examination of Paint
Basecoat (color layer) provides the most evidence because of paint chemical composition
Layering of paint also helps forensic scientists determine a common point of origin

45. Value of Paint Examination
Chemical composition of different paints can be linked to different makes and models of automobiles and can assist in locating a suspect vehicle

46. Collection and Preservation of Paint Evidence
Loose paint chips can be picked up with forceps and placed in envelopes or tight-lid containers
Reference samples must be taken in an area adjacent to the missing paint chip by using a scalpel or razor blade