Hairs & Fibers

Morphology and Structure of Hair

Morphology of Hair

An appendage of the skin that grows out of an organ known as the hair follicle.

Extends from its root or bulb embedded in the follicle, continues into a shaft, and terminates at a tip end.

The Shaft of Hair

Composed of three layers: cuticle, cortex, and medulla.

Morphology: Cuticle Protective coating made of

overlapping scales, produce a characteristic pattern

Scales always point toward tip of hair

Not useful in individualizing human hair

Can be used for species identification

http://www.pg.com/science/haircare/hair_twh_35/hair_twh_35_02.jpg

Preserving scale pattern

Since examination of internal structure of hair requires loss of scale pattern, a scale case is made.

Clear nail polish on microscope slide

Hair embedded and allowed to dry before removed.

Differences between animal hairs and human hairs

There are three basic scale structures that make up the cuticle—coronal (crown-like), spinous (petal-like), and imbricate (flattened). Combinations and variations of these types are possible.

http://www.fbi.gov/hq/lab/fsc/backissu/jan2004/research/2004_01_research01b.htm

Differences between animal hairs and human hairs

The coronal, or crown-like scale pattern is found in hairs of very fine diameter and resemble a stack of paper cups. Coronal scales are commonly found in the hairs of small rodents and bats but rarely in human hairs.

http://www.fbi.gov/hq/lab/fsc/backissu/jan2004/research/2004_01_research01b.htm

Differences between animal hairs and human hairs

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.

http://www.fbi.gov/hq/lab/fsc/backissu/jan2004/research/2004_01_research01b.htm

Differences between animal hairs and human 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.

Differences between animal hairs and 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 distribution and density of pigment in animal hairs can also be identifiable features. The pigmentation of human hairs is evenly distributed, or slightly more dense toward the cuticle, whereas the pigmentation of animal hairs is more centrally distributed, although more dense toward the medulla.

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.

Morphology: Cortex Made of spindle-shaped

cells aligned in a regular array, parallel to the length of the hair

Embedded with pigment granules that give hair its color

The color, shape and distribution of the granules provide points for forensic comparison

www.pg.com/science/haircare/hair_twh_59.htm

Your natural Hair color is determined by three factors

1. The type of natural color pigment

melanin present in your hair's cortex.

Eumelanin (black pigment)

Phenomelanin (red/yellow pigment)

2. How many melanin granules exist

3. Whether those granules are close together or far apart

How Melanin pigments determine your natural haircolor:

Black hair contains densely packed melanin granules full of

eumelanin. Brown hair has a loose pattern of eumelanin-filled

granules or granules blended with eumelanin and phenomelanin, depending upon its cool or warm tones and its darkness or lightness.

Blonde hair contains few granules with minimal bits of

eumelanin. In fact, the eumelanin is so sparse that the color of blonde hair is the color of the hair fiber itself.

Red hair has loosely packed granules containing

phenomelanin.

What causes gray hair? As you age, your natural production of

pigment slows down and your natural color loses its color strength.

This doesn't happen to every hair at the same time, so the contrast between the hair with no color and the hair that still has some color causes it to look gray.

So how gray your hair actually looks is determined by the percentage of strands with no color vs. the pigmented strands.

Morphology: Medulla

canal like structure of cells that runs through the center of the cortex

Medullary Index

Measure of the diameter of the medulla relative to the diameter of the hair shaft

Usually expressed as a fraction

Humans: medullary index < 1/3

Animals: medullary index > 1/2

Medullae of Different Species

Medulla Shape Medulla shape is another characteristic

that varies from species to species

UNISERIAL (rabbit)

MULTISERIAL (rabbit)

VACUOLATED (dog, fox,

common)

LATTICE (deer)

AMORPHOUS (human,

common) 20

Medulla of Different Species

Forensic Analysis of Medulla Presence of medulla varies quite a bit: even hair

to hair Human head hairs generally have no medulla or

may be fragmented ones; except Mongoloid (Asian) race whose medulla is usually continuous

Most animals have medulla that is continuous or interrupted

The shape of the medulla can help identify a species

Examples: Most animals and humans: cylindrical Cats: pearl shape Deer: spherical occupying whole hair shaft

Comparison of Animal and Human Hair

Medullary Index ≥1/2

Medulla is present for all animals

Medulla is continuous for most animals

Medulla is patterned for most animals

Medullary Index <1/3

Medulla is absent for most humans

Medulla is continuous for Mongoloid race

Medulla is fragmented – only some animals and humans

Medulla is cylindrical in shape (most animals)

Identification and Comparison of Hair

Morphological Characteristics do not allow individualization of a human hair to any single head or body

Hair when collected with an adequate number of standards/references can provide strong circumstantial evidence

Scale structure, medullary index, and medullary shape are most often used for hair comparison

Evidential value lies with degree of probability associated with a questioned hair and an particular individual

11 percent of all morphological hair matches are generally found to be non-matches—meaning microscopic hair comparisons are presumptive in nature—must be confirmed by DNA comparisons

Human Hairs

Racial Determination

Body Area

Age and Sex?

Forcibly Removed?

Can the racial origin of hair be determined?

Forensic terms: Caucasoid, Negroid, Mongoloid

Mongoloid has continuous medullae

Caucasian has even distribution of pigment in cortex

Negroid has unevenly distributed pigment.

http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric1.htm

Racial Determination

Negroid

Mongoloid

Caucasoid

Usually kinky, containing dense, unevenly distributed pigments.

Cross section is flat to oval in shape.

Usually straight or wavy with very fine to coarse pigments that are more evenly distributed .

Cross section are oval to round in shape.

Usually coarse containing pigment granules larger in size than Caucasians.

Cross sections are round in shape.

Head Hairs

Long with moderate shaft diameter and diameter variation

Medulla absent to continuous and relatively narrow when compared to the structure of hairs from other body areas

Often with cut or split tips

Can show artificial treatment, solar bleaching, or mechanical damage

Soft texture, pliable

Pubic Hairs

Medulla relatively

broad and usually

continuous when

present

Root frequently

with tag

Tip usually tapered, rounded, or

abraded

Stiff texture, wiry

Shaft diameter

coarse with

wide

variations and

buckling

Limb Hairs

Tips usually tapered, often blunt and abraded, rounded scale ends due to wear

Diameter fine with little variation Gross appearance of hair is arc-like in shape

Medulla is discontinuous to trace with a granular appearance

Soft texture

Facial Hairs (Beard/Mustache)

Diameter very coarse with irregular or triangular cross-sectional shape

Medulla very broad and continuous, may be doubled

Chest Hairs

Shaft diameter moderate and variable

Tip often darker in color, long and fine, arc-like

Medulla may be granular

Stiff texture

Axillary or Underarm Hairs

Resemble pubic hairs in general appearance, but less wiry

Medullary appearance similar to limb hairs

Diameter moderate and variable with less buckling than pubic hairs

Tips long and fine, frequently with bleached appearance

Other Body Hairs

Eyebrow: Stubby, some diameter fluctuation, saber-like in appearance

Eyelash: Short, stubby with little shaft diameter fluctuation, saber-like in appearance

Trunk: A combination of features of limb and pubic hairs, a transitional hair

Tip of the Shaft

Burned Cut Razored Split

Root of Hair

Provide the tools to produce hair and continue its growth

3 Stages of Growth (different looking roots) Anagen -initial phase may last up to 6 years, root is

flame shaped Catagen –transition phase (2-3 weeks), root is

elongated Telogen –phase where hair naturally falls out of the

skin, root is club-shaped

Hair Growth Cycle

Forcibly Removed?

Pulled Forcibly Removed Shed

A normal telogen hair with a

hard 'club' end, seen under

(left) a light microscope and

(right) an electron microscope

An anagen hair that has been

plucked out: notice the soft,

sticky tail

Brushed-out hairs all have

this kind of root.

This is an anagen hair,

one which was pulled

out and not ready to be

shed.

Collection of Hair Evidence

Collection of Hair Evidence

Questioned and Reference hair must come from same area of the body; one cannot, for instance compare head hair to pubic hair.

The collection of 50 full length hairs from all areas of the scalp will normally ensure a representative sampling of head hair.

Collection of Hair Evidence

A minimum collection of 24 full length pubic hairs should cover the range of characteristics present in this type of hair.

All collected hairs must be full-length so that the investigator can see if the color and morphological features vary throughout the length of the hair.

Packaging of Hair Evidence

Recover all hair present. If possible, use fingers or tweezers to pick up

hair, place in paper bindles or coin envelopes which should then be folded and sealed in larger envelopes.

Label the outer sealed envelope. If hair is attached, such as in dry blood, or

caught in metal or a crack of glass, do not attempt to remove it but rather leave hair intact on the object.

If the object is small, mark it, wrap it, and seal it in an envelope.

If the object is large, wrap the area containing the hair in paper to prevent loss of hairs during shipment

Fibers: Natural Derived entirely from animal or

plant sources

Most prevalent plant fiber is cotton.

Its widespread use has made its evidential value almost meaningless

Cotton has a ribbon-like shape with twists at regular intervals

Animal sources include sheep (wool), goats (mohair, cashmere) and many other sources

http://www.swicofil.com/images/cotton_microscopic.jpg http://www.e4s.org.uk/textilesonline/content/6library/report1/images/microscope_2.gif

Wool

Cotton

Man-Made Fibers

Fibers derived from either natural or synthetic polymers

The fibers are made by forcing polymeric material through the holes of a spinneret

Rayon and then nylon were the first two man-made fibers (year 1911)

http://www.naturalvisions.co.uk/pictures/thumbnail/XMIC_0021_0001XX.jpg

Man-Made Fibers Con’t Regenerated Fibers

Made from regenerated cellulose (wood or cotton pulp)

Include such fibers as rayon, acetate, and triacetate

Synthetic Fibers Currently manufactured

Made from synthetic chemicals called polymers

Include such fibers as nylons, polyesters, and acrylics

ID and Comparison of Man-Made Fibers

Fabrics that can be fitted together at their torn edge are easy to match

Microscopic comparison of color and diameter

Comparison of lengthwise striations and pitting on the surface of a fiber

The shape of the fiber—ex. Wayne Williams case Cross sections are generally helpful

Note: Combined factors of color, size, shape, microscopic appearance, chemical composition, and dye content make it very unlikely to find two different people wearing identical fabrics

ID and Comparison of Man-Made Fibers con’t.

The chemical makeup of the fiber itself can be examined through the following:

Infrared microspectrophotometry

Refractive Index

The chemical makeup of the dyes in the fiber can be examined through the following:

Liquid chromatography

Visible light microspectrophotometry