Lesson 5 Trace Evidence: Hair and Fiber

History• 1916 - Albert Schneider

became the first to collect physical evidence with a vacuum.

• 1920 - Locard becomes known for the exchange principle – the fact that “every contact leaves a trace.”

• 1931 - Dr. Paul Kirk works on new ways to improve the use of hair in forensic investigations.Edmond Locard (1877-1966),

noted for his exchange principle.

• 1891 - Han Gross published the first description of the uses of physical evidence to help solve crimes.

• 1897 - Rudolph Virchow became the first person to do an in-depth study of hair.

• 1906 - Hugo Marx wrote a paper on the use of hair in forensic investigations to determine identity.

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

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

Hair Morphology

Hair Morphology• The most basic components

of hair are keratin, a very strong protein that is resistant to decomposition, and melanin, a pigment.

• The keratins form groups that interact and interconnect to form very stable fibrils. It is this property of hair that makes it such a prime example of physical evidence.

Hair Morphology

• Hairs are dead. The portion existing above the epidermis is called the shaft; below the epidermis, the root (or bulb) is embedded in the hair follicle.

•The hair shaft is composed of three layers:− Cuticle− Cortex− Medulla

Cuticle

• Protective coating made of overlapping scales

• Produces a characteristic pattern• Scales always point toward tip

of hair.• Not useful in individualizing

human hair• Useful for species identification http://www.pg.com/science/haircare/hair_twh_35/hair_twh_35_02.jpg

Cuticle• The cuticle of a hair is the thin,

translucent layer surrounding the shaft. It consists of scales of hardened, keratinized tissue that vary from species to species and includes such patterns as:– Coronal, or “crown – like.” Rare in

humans; typical of rodents. Found in hairs of very fine diameter.

– Spinous, or “petal – like.” Neverfound in humans. Common in cats, seals, and minks.

– Imbricate, or “flattened.” Common in humans.

Coronal

Spinous

Imbricate

Cuticle

Photomicrograph of a mink hair possessing a Spinous cuticle.

Photomicrograph of a bat hair possessing a Coronal cuticle.

Photomicrograph of a human hair possessing an Imbricate cuticle.

Cuticle: Examination • Examination of internal structure

of hair means loss of scale pattern.

• To examine the scale pattern, a scale case is made.

• Clear nail polish is brushed on a on microscope slide.

• Hair is embedded and allowed to dry before being removed.

• The nail polish contains an impression of the scale pattern that can be examined under a microscope for identification.

Cortex• The cortex is the main body of

the hair, composed of spindle-shaped cortical cells.

• Contains pigment granules, which contain the melanin (hair color), and cortical fusi.– Cortical fusi are air spaces of

varying sizes found near the root of a mature human hair.

– Pigment granules are small, dark, granulated structures that vary in size, color, and distribution. Typically distributed toward the cuticle in humans.

• Bleached hair is devoid of pigment granules, and dyed hair has dye in the cuticle and the cortex.

Photomicrograph of cortical fusi in human hair

Photomicrograph of pigment distribution in human hair

• The cortex is made of spindle-shaped cells aligned in a regular array, parallel to the length of the hair.

• It is 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

Cortex

Your natural hair color is determined by three factors:– The type of melanin present in your hair's cortex.

• Eumelanin (black pigment) • Phenomelanin (red/yellow pigment)

– How many melanin granules exist – Density of melanin granules - are they close

together or far apart?

Cortex

CortexBlack Hair•Densely packed granules•Eumelanin

Brown Hair•Loose pattern of granules•Mix of eumelanin and phenomelanin

Blonde Hair•Few granules •Very little eumelanin•Color is really the color of the hair fiber itself

Red Hair•Loose granules •Packed with 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.

Cortex

Medulla• The medulla is a central core of cells

that runs through the center of the cortex.

• The medulla may be:– Continuous– Fragmented– Interrupted

• In human hairs, the medulla is generally amorphous in appearance or completely absent.

• In animal hairs, its structure is frequently very regular and well defined.

• Medullar index is the diameter of the medulla divided by the diameter of the cortex. In humans the ratio is less than 1/3 and more than ½ in animals.

Medulla

Photomicrograph of a human hair with no medulla.

Photomicrograph of a hair with trace medulla.

Photomicrograph of a hair with a clear, continuous medulla.

Medulla shape is another characteristic that varies from species to species

MULTISERIAL (rabbit)

VACUOLATED (dog, fox, common)

LATTICE (deer)

AMORPHOUS (human, common)17

Medulla

Medullae of Different Species

• Presence of medulla varies quite a bit: even hair to hair

• Human head hairs generally have no medulla or may have fragmented ones. The exception is the Mongoloid (Asian) race, whose medulla is usually continuous

• Most animals have a 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

Medulla

Comparison of Animal and Human Hair

Medullary Index ≥1/2

Medulla is present for all animals

Medulla is continuous for most

animalsMedulla 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 a particular individual.

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

Human Hairs• Racial Determination• Body Area• Age • Forcibly Removed• Tip of Shaft

Can the racial origin of hair be determined?

• Forensic terms: – Caucasoid – Negroid– Mongoloid

• Mongoloid has continuous medullae.

• Caucasoid has even distribution of pigment in cortex.

• Negroid has unevenly distributed pigment.

http://ww

w.fbi.gov/hq/lab/fsc/backissu/july2000/deedric1.htm

Negroid Hairs• Curly• Dense pigment

distributed unevenly• Variations in the

diameter of the shaft. Fragmented or absent medullae

• The cross-section is flattened.

Cross Section of a Negroid Hair

Photomicrograph of a Negroid Head Hair

Mongoloid Hairs• Coarse and straight shaft,

with little diameter variation

• Dense pigment distributed unevenly

• Presence of a continuous medulla

• The cross-section is round.

Cross Section of a Mongoloid Hair

Photomicrograph of a Mongoloid Head Hair

Caucasian Hairs

• Straight to wavy• Fairly evenly distributed,

fine pigment• Moderate shaft diameter,

with little variation• The cross-section is oval.

Cross Section of Caucasian Hair

Photomicrograph of a Caucasian Hair

Body Area

• Head• Pubic• Limb• Facial• Chest• Underarm• Brows• Lashes

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

•Tip usually tapered, rounded, or abraded

•Stiff texture, wiry

Medulla relatively broad and

usually continuous

when present

Shaft diameter coarse with

wide variations and

buckling

Root frequently with tag

Limb Hairs•Diameter fine with little variation •Appearance of hair is arc-like in shape •Soft texture•Tips usually tapered, often blunt and abraded, rounded scale ends due to wear•Medulla is discontinuous to trace with a granular appearance

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• Brows: Stubby, some

diameter fluctuation, saber-like in appearance

• Lashes: Short and stubby with little shaft diameter fluctuation, saber-like in appearance

Age: Root of Hair• Age can’t be determined other than infant hair. Infant hair

is fine, short in length, has fine pigment, and is rudimentary in character.

• Dye or bleach may offer some clues as to sex; but with current hair styles and fashions, it is less valuable than in the past.– Currently, researchers are making progress in determining the

sex origin of human hair. – Most of this research has concentrated on using techniques for identifying

genetic substances in human cells.– At this time sexual discrimination of hair cells in not considered to be a

routine forensic technique.

Forcibly Removed

Pulled Forcibly Removed Shed

Tip of the Shaft

Burned Cut Razored Split

Fiber EvidenceA fiber is the smallest unit of a textile material that has a length many timesgreater than its diameter. A fiber can be spun with other fibers to form a yarn thatcan be woven or knitted to form a fabric.

The type and length of fiber used, the type of spinning method, and the type offabric construction all affect the transfer of fibers and the significance of fiberassociations. This becomes very important when there is a possibility of fibertransfer between a suspect and a victim during the commission of a crime.

http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric3.htm#Fiber%20Evidence

Matching unique fibers on the clothing of a victim to fibers on a suspect’s clothingcan be very helpful to an investigation, whereas the matching of common fiberssuch as white cotton or blue denim fibers, would be less helpful.

The discovery of cross transfers and multiple fiber transfers between the suspect'sclothing and the victim's clothing dramatically increases the likelihood that thesetwo individuals had physical contact.

Fiber

• Fiber is often the most common type of evidence found at a crime scene.

• Importance is usually magnified in cases of homicide, assault, or sexual offences.

• Fibers may be found• Caught in screens, or on jagged surfaces• Around broken glass• On cars involved in pedestrian hit and runs• Transferred during a struggle

• 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

Natural Fibers

Images: http://www.trashforteaching.org/phpstore/product_images/YarnWS.JPG http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric3.htm#Fiber%20Evidence

http://www.jivepuppi.com/images/fiber_evidence.jpg

•Fibers derived from either natural or synthetic polymers•The fibers are made by forcing polymeric material through the holes of a spinneret.• In 1911, Rayon and then nylon were the first two man-made fibers.

Cross-section of a man-made fiber

Synthetic Fibers

Fibers under a microscope

Synthetic Fibers

• 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 Synthetic 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• 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

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

ID and Comparison of Synthetic Fibers

Examine hairs and fibers!

Directions:

1. Your team will need to use a microscope to document all the hairsand fibers in your set.

2. Write the name of the hair or fiber on the line and then draw whatyou see under medium or high power. Be sure to indicate thepower of magnification!

3. Add a description that highlights the unique characteristics ofeach hair and fiber sample.

4. Pay attention to details to help you identify evidence later in achallenge.

Hair & Fiber Identification

References• James, Stuart. Forensic Science. 2. Boca Raton, FL: CRC Press, 2005. • Bell, Suzanne. Forensic Chemistry. 1. Upper Saddle River, NJ: Pearson Prentice

Hall, 2006. • Girard, James E.. Criminalistics: Forensic Science and Crime. 1. Sudbury, MA:

Jones and Barlett Publishers Inc., 2008. • Saferstein, Richard. Criminalistics: An Introduction to Forensic Science. 9. Upper

Saddle River, NJ: Pearson Prentice Hall, 2007. • Deedrick, Douglas. "Hairs, Fibers, Crime and Evidence." Forensic Science

Communications 2.3July 2000 16 003 2008 <http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric1.htm>.

• Kathy, Steck-Flynn. "Trace Evidence: Hair." Crime and Clues: The Art and Science of Criminal Investigation. 03 009 2006. 16 Mar 2008 <http://www.crimeandclues.com/hair_evidence.htm>.

• Bisbing, Richard E., (2001) Finding Trace Evidence. in Mute Witnesses: Trace Evidence Analysis. Houck, Max., (ed.) Academic Press, San Diego, California

• www.coolphysics.org/Hair,%20Fiber,%20and%20Paints%2005.ppt• Hamrick, Barbara. "Uranium in Hair Analysis: Responding to Public Concerns." 25 004

2004. Environmental Nuclear Council. 16 Mar 2008 <http://www.crcpd.org/AnnualMeeting-04/05-25-04_0810-Hamrick.pdf>.