1. HAIR, FIBERS, AND PAINT

2. Introduction HAIR FIBERS AND PAINT
Hair is encountered as physical evidence in a wide variety of crimes.
Although it is not yet possible to individualize a human hair to any single head or body through its morphology, it still has value as physical evidence.
When properly collected and submitted to the laboratory accompanied by an adequate number of standard/reference samples, hair can provide strong corroborative evidence for placing an individual at a crime scene.
HAIR FIBERS AND PAINT

3. Morphology of Hair HAIR FIBERS AND PAINT
Hair is an appendage of the skin that grows out of an organ known as the hair follicle.
The length of a hair extends from its root or bulb embedded in the follicle, continues into a shaft, and terminates at a tip end.
It is the shaft, which is composed of three layers—the cuticle, cortex, and medulla—that is subjected to the most intense examination by the forensic scientist.
HAIR FIBERS AND PAINT

4. Structure of Hair

5. Hair Structure Hair is composed of three principal parts:
Cuticle – outer coating composed of overlapping scales
Cortex – protein-rich structure around the medulla that contains pigment
Medulla – central core (may be absent)
The structure of hair has been compared to that of a pencil with the medulla being the lead, the cortex being the wood and the cuticle being the paint on the outside.

6. Cuticle and Cortex HAIR FIBERS AND PAINT The cuticle is the scale
structure covering the
exterior of the hair.
The scales always point towards the tip of the hair.
The scale pattern is useful in species identification.
The cortex is the main body of the hair shaft.
Its major forensic importance is the fact that it is embedded with the pigment granules that impart hair with color.
The color, shape, and distribution of these granules provide the criminalist with important points of comparison among the hairs of different individuals.
HAIR FIBERS AND PAINT

7. Hair Structure Cuticle The cuticle varies in: Its scales,
How many there are per centimeter,
How much they overlap,
Their overall shape, and
How much they protrude from the surface
Its thickness, and
Whether or not it contains pigment.
Characteristics of the cuticle may be important in distinguishing between hairs of different species but are often not useful in distinguishing between different people.
Info: Image:

8. Imbricate, Coronal, Spinous Cuticles

9. Hair Structure Cortex The cortex varies in: Thickness Texture Color
Distribution of the cortex is perhaps the most important component in determining from which individual a human hair may have come.
Cortical fusi: air spaces
Microscopic examination can also reveal the condition and shape of the root and tip.
Info: Image:

10. Medulla HAIR FIBERS AND PAINT
The medulla is a cellular column running through the center of the hair.
The medullary index measures the diameter of the medulla relative to the diameter of the hair shaft.
For humans, the medulla generally occupies less than one-third the diameter of the shaft, while for animals it is generally one-half or greater.
The medulla may be continuous, interrupted, fragmented, or absent.
The presence of the medulla varies from individual to individual and even among hairs of a given individual.
Medullae also have different shapes, depending the species.
HAIR FIBERS AND PAINT

11. Hair Structure Medulla The medulla may vary in: Thickness
Continuity - one continuous structure or broken into pieces
Opacity - how much light is able to pass through it
It may also be absent in some species.
Like the cuticle, the medulla can be important for distinguishing between hairs of different species, but often does not lend much important information to the differentiation between hairs from different people.

12. MEDULLA- The medulla is the core of a hair that is not always present
MEDULLA- The medulla is the core of a hair that is not always present. There are several types and patterns.
TYPES:
Continuous
Intermittent or interrupted--even breaks in the medulla
Fragmented--breaks that are unevenly spaced
Absent
PATTERNS: 
Uniserial--small blocks in a row
Multiserial--several rows of blocks across
Vacuolated--uneven pattern
Lattice--circular patterns

13. Cat- Uniserial Squirrel-Vacuolated
Multiserial- rabbit Lattice- deer

14. Unique Hairs! Ringed Seal hair Elk Guard Hair
Northern Fur Seal Guard Hair
Snow Shoe Hair
Tiger Hair
Polar Bear hair

15. Root
The root and other surrounding cells in the hair follicle provide the tools necessary to produce hair and continue its growth.
When pulled from the head, some translucent tissue surrounding the hair’s shaft near the root may be found. This is called a follicular tag.
By using DNA analysis on the follicular tag, the hair may be individualized.
HAIR FIBERS AND PAINT

16. Roots with Follicular Tags

17. Hair grows in three phases:
anagen phase- the initial growth phase during which the hair follicle is actively producing hair, may last up to 6 years. Root is attached to follicle giving the root bulb a flame shaped appearance. When pulled from the root, a hair in this phase will have a follicular tag (translucent piece of tissue near root containing a rich supply of DNA.
catagen phase- transition phase between the anagen and telogen phases of hair growth. Decreased rate of growth lasts 2-3 weeks. Catagen roots have an elongated appearance as the root bulb shrinks in size and is being pushed out of the hair follicle.
telogen phase- Hair growth ends and root takes on a club appearance. Lasts 2- 6 months. Hair is pushed out of the follicle and naturally shed.

18. Phases of Hair Growth

19. Comparing Strands HAIR FIBERS AND PAINT
The comparison microscope is an indispensable tool for comparing the morphological characteristics of hair.
When comparing strands of human hair, the criminalist is particularly interested in matching
the color, length, and diameter.
presence or absence of a medulla
distribution, shape, color intensity of the pigment granules in the cortex
Whether the hair was bleached (shows a yellowish tin) or dyed (dye pigments appear in the cortex as well as the cuticle) and when a color job was done (natural root portion, distinct in color, grows about 1 cm per month)
Morphological abnormalities- disease, deficiencies, fungal or nit infections.
HAIR FIBERS AND PAINT

20. A careful microscopic examination of hair will reveal morphological features that can distinguish human hair from the hair of animals.
Scale structure, medullary index, and medullary shape are particularly important in animal hair identification.
There is a high error rate in linking through hair analysis by morphology, but with DNA analysis a definitive match can be made. (As long as DNA is found with the hair.)

21. Caucasian:
Shaft diameter: moderate with little variation Cross Section: oval Pigment granules evenly distributed

22. African:
Shaft diameter: fine to moderate with considerable variation Cross Section: flattened Pigment granules: clumped

23. Asian:
Shaft diameter: moderate with little variation Cross Section: round Pigment granules: large patchy areas Continuous medulla

25. Questions HAIR FIBERS AND PAINT
Can the body area from which a hair originated be determined?
Yes!
scalp hairs are relatively uniform in diameter and distribution of pigment
pubic hairs are short and curly with wide variety in shaft diameter and usually have continuous medullae.
Beard hairs are coarse and triangular in cross section with blunt ends due to trimming
Can the racial origin of hair be determined?
Usually when dealing with Negroid and Caucasian Hairs, however, the observations are general in nature, with many exceptions to the rule.
Can the age and sex of an individual be determined from a hair sample?
Infant hair can be determined because it is fine, short in length, has fine pigment.
Nuclear DNA analysis from tissue adhering to the hair or from the root can be used to determine if the hair is from a male or female.
HAIR FIBERS AND PAINT

26. Hair and DNA HAIR FIBERS AND PAINT
Is it possible to determine if a hair was forcibly removed from the body?
A hair root with follicular tissue attached can be indicative of a hair that has been pulled out.
Are efforts being made to individualize human hair?
Nuclear DNA analysis of DNA from hair roots in the anagen or catagen growth phases can be used to ID a person. Also hair that has been forcibly removed has enough DNA to analyze.
Mitochondrial DNA analysis can be done when there is not enough nuclear DNA to analyze due to the high quantity in each cell. Mitochondrial DNA is passed from mother to child and analyzing hair in length from 1-2 cm can lead to highly successful results.
Can DNA individualize a human hair?
Nuclear DNA will produce a frequency as low as 1 in billions or one in trillions
Mitochondrial DNA will not individualize a human hair but it can often allow a scientist to exclude a significant portion of the population.
HAIR FIBERS AND PAINT

27. "It's just a formality, but I'll also need a lock of your hair for DNA analysis."

28. Collection and Preservation
Standard/reference hairs must be representative, from the same part of the body as the questioned hair.
The collection of 50 full-length hairs from all areas of the scalp will normally ensure a representative sampling of head hair.
A minimum collection of two dozen full-length pubic hairs should cover the range of characteristics present in pubic hair.
Hair samples are also collected from the victims of suspicious deaths during an autopsy.
HAIR FIBERS AND PAINT

30. Can you identify the animal hairs shown?B C D G E F H I
Teacher Note: I challenge students to identify each hair sample pictured on this slide as they examine the sets of animal hairs I have prepared for them. An observation worksheet is available on my website which requires students to draw an image of what they see and add a description that highlights unique characteristics of each specimen. A key for the animal hairs is available on the next to last slide of this presentation!
Think About It …
In which samples are we viewing the cuticle? How do they compare?
(2) In which samples are we viewing the medulla? How do they compare?
(3) What characteristics can be used to identify hair samples? 30

31. Types of Animal Hairs - Key
Cat
Horse
Pig
Human A B C D G E F H I
Deer
Dog
Rabbit
Guinea Pig
Human 31

32. Fibers and Forensics
can be found at a hit and run crime scenes attached to the vehicle
can become fixed in screens or glass at break-and-entering crime scenes
value as evidence depends on the criminalizes ability to narrow the origin to a limited number of sources
Recovery of fibers at a crime scene usually will not provide individual identification with a high degree of certainty

33. Types of Fibers cotton HAIR FIBERS AND PAINT
Natural fibers are derived in whole from animal or plant sources.
Examples: wool, mohair, cashmere, furs, and cotton.
Cotton is the most common fiber found and therefore insignificant
Wool
HAIR FIBERS AND PAINT

34. Types of Fibers Man-made fibers are manufactured.
Regenerated fibers are derived from cotton or wood pulp which has been chemically treated and dissolved in a solvent. The mass is then forced through the holes of a spinning jet to produce the fibers. Ex.- rayon, acetate, and triacetate.

35. Types of Fibers
Synthetic fibers are produced solely from synthetic chemicals and include nylons, polyesters, and acrylics.
nylon cross section

36. Types of Fibers
Polymers, or macromolecules, are synthetic fibers composed of a large number of atoms arranged in repeating units known as monomers. Glucose is the monomer in the polymer starch.
by varying the chemical structure of the monomer and devising numerous ways to link them together, chemists have created polymers that exhibit different properties.
Versatility allows for the synthesis of glue, plastics, paints and fibers
Cellulose is a natural polymer

37. Again- Types of Fibers! plants (cotton, hemp, etc.)
animal (wool, silk, etc.)
mineral (asbestos, fiberglass, etc)
man-made (nylon, polyester, etc).

38. Classification of Fibers

40. Fiber Evidence
The quality of the fiber evidence depends on the ability of the criminalist to identify the origin of the fiber or at least be able to narrow the possibilities to a limited number of sources.
Obviously, if the examiner is presented with fabrics that can be exactly fitted together at their torn edges, it is a virtual certainty that the fabrics were of common origin.
HAIR FIBERS AND PAINT

41. The Best Type of Fabric Evidence

42. Fiber Evidence HAIR FIBERS AND PAINT
Microscopic comparisons between questioned and standard/reference fibers are initially undertaken for color and diameter characteristics, using a comparison microscope.
Other morphological features that could be important in comparing fibers are:
Lengthwise striations on the surface of the fiber
The presence of delustering particles that reduce shine, pitting
The cross-sectional shape of the fiber
Compositional differences may exist in the dyes that were applied to the fibers during the manufacturing process.
HAIR FIBERS AND PAINT

43. Methods For Fiber Comparison
The visible light micro spectrophotometer can be used to show that 2 fibers have the same dye composition by comparing spectral patterns.
Thin layer chromatographic separation can be used to separate the dye components of 2 fibers which are then compared.
Many manufactured fibers exhibit double refraction so 2 fibers can be compared by the differences in their bifringence..
HAIR FIBERS AND PAINT

44. Methods For Fiber Comparison
Both the questioned fiber and the standard/reference fiber must also be shown the have the same chemical composition to confirm that they belong to the same subclass of fibers.
There is no data base for determining a fibers origin.
There is no analytical technique that permits a criminalist to definitely associate a fiber strand to one garment.
The more fibers available to analyze and match as close as possible and other types of physical evidence will help link a person or object to a crime.

45. Collection and Preservation
The investigator’s task of looking for minute strands of fibers often becomes one of identifying and preserving potential “carriers” of fiber evidence- time consuming and tedious!!.
Relevant articles of clothing should be packaged carefully in separate paper bags.
If it is necessary to remove a fiber from an object, the investigator must use clean forceps, place it in a small sheet of paper, fold and label the paper, and place the paper packet inside another container.
HAIR FIBERS AND PAINT

46. Collection and Preservation
Carpets, rugs and bedding should be folded to protect attached fiber evidence
Car seats and knife blades should be covered with plastic to protect adhering fibers.

48. Can you identify the types of fibers shown?
Teacher Note: I challenge students to identify each fiber sample pictured on this slide as they examine the sets of fibers I have prepared for them. An observation worksheet is available on my website which requires students to draw an image of what they see and add a description that highlights unique characteristics. A key for the fibers is available on the last slide of this presentation!
Think About It …
Which samples are natural fibers?
(2) Which samples are synthetic fibers?
(3) What characteristics can be used to identify fiber samples? 48

49. A B C D E F Types of Fibers - Key Acrylic Yarn Cotton Yarn Nylon Rope
Polyester Yarn
Rayon Rope
Wool Yarn 49

50. Paint HAIR FIBERS AND PAINT
Paint- pigments and additives suspended in a binder dissolved in a solvent. When the solvent dries the hard binder and the pigments are left on the painted surface.
Pigments impart color and hiding (opacity) to paint.
Binder provides the support medium.
One of the most common types of paint examined in the crime laboratory involves finishes emanating from automobiles.
Automobile manufacturers normally apply a variety of coatings to the body of an automobile.
These coatings may include electrocoat primer, primer surfacer, basecoat, and clearcoat.
HAIR FIBERS AND PAINT

51. Automobile Paint- types
Electrocoat Primer- the 1st layer consisting of epoxy-based resins, is electroplated onto the steel body of the car to provide corrosion resistance. Color ranges from gray to black
Primer Surfacer- 2nd layer applied to the electrocoat primer. This layer is made of epoxy-modified polyesters or urethanes and functions to completely smooth out and hide any imperfections. This layer is highly pigmented and color is chosen to minimize color contrast between primer and topcoats.
Basecoat- 3rd layer that provides color and aesthetics of the finish and provides “eye-appeal”. This layer is designed to resist the elements of weather, UV rays, and acid rain. Most commonly this layer is made of an acrylic-based polymer binder and organic-based pigments.
Clearcoat- an unpigmented clearcoat is applied to improve gloss, durability and appearance. Most are acrylic-based.

52. Methods For Paint Comparison
The wide diversity of automotive paint contributes to the forensic significance of an automobile paint comparison. Color gives paint its most distinctive forensic characteristics
Questioned and known specimens are best compared side by side under a stereoscopic microscope for color, surface texture, and color layer sequence.
Pyrolysis gas chromatography and infrared spectrophotometry are invaluable techniques for distinguishing most paint binder formulations, adding further significance to a forensic paint comparison.
Crime laboratories are often asked to identify the make and model of a car from a small amount of paint and will make use of color charts for automobile finishes. Paint Data Query (PDQ) is used to match make, model and year using information on paint layer colors, primer colors and binder composition.
HAIR FIBERS AND PAINT

53. Paint evidence

54. Collection and Preservation
Paint chips are most likely found on or near persons or objects involved in hit-and-run incidents.
Paper druggist folds and glass or plastic vials make excellent containers for paint.
Paint smeared or embedded in garments or objects require the whole item to be packaged and sent to the laboratory.
Uncontaminated standard/reference paint must always be collected.
1/4th inch standard /reference paint layer sample must be removed with a clean knife to the bare metal for layering comparisons, from all cars involved.
Samples need to be labeled as to location of recovery.
Tools used to gain entry into buildings or safes often contain traces of paint, requiring the tool be collected, along with reference paint samples.
HAIR FIBERS AND PAINT