Hairs, Fibers, and Paint

Chapter 8

Dermis• Contains

- smooth muscle- blood vessels- nerve tissue- hair follicles (accessory organ of skin)- sweat glands (accessory organ of skin)- sebaceous glands (accessory organ of skin)

• Contains nerve receptors – to sense light/heavy touch or pressure

• Contains connective tissue made of collagen and elastic fibers

Full-thickness Skin

Accessory Organs of the Skin

• Hair follicles

• Nails

• Skin glands– Sebaceous glands– Sweat glands (a.k.a sudoriferous glands)

• Eccrine• Apocrine

Hair Follicles

• Follicles are present on all skin excepts palms, soles, lips, nipples

• In some areas that grow hair, the hair may be fine, while in others it may be thick

• A hair grows out of a deep tube that extends from the surface of the skin, all the way into the dermal layer – this is a follicle

• Each hair follicle is also connected to sebaceous glands that produce oils and other secretions

Hair Follicle, cont’d.

• The follicle contains the growing hair shaft

• The base of the hair is composed of actively dividing epidermal cells

• These epidermal cells are nourished by dermal blood vessels near the hair base – this area at the base of the hair follicle is called the hair papilla

Hair Growth• As the epidermal cells divide,

they push older cells upward through the follicle

• As the older cells move away from the nutrient supply, they become keratinized and die

• These dead keratinized epidermal cells are what make up a strand of hair

• Hair color is genetically determined and is pigmented by melanocytes - the more the melanin in the dead epidermal cells, the darker the hair

Phases of Hair Growth

1. Anagen – can last up to 6 years. In this phase, the hair root is still attached to the hair follicle and grows. The root appears plump and “flame-shaped”

2. Catagen – the hair continues to grow, but at a slower rate. This slowed-down growth rate can last for 2 to 3 weeks. The root bulb shrinks and appears elonated.

3. Telogen – Telo means “end”. This is the phase in which the root begins to look like a club. The hair will slowly get pushed out of the follicle. This slow loss can take 2 to 6 months.

A strand of hair has three layers: cuticle, cortex, and medulla.  The outermost covering, cuticle consists of hard overlapping protein scales that point toward tips end.  The cortex contains pigment granules that give hair its color.  The medulla is a hollow tube within the hair, which may be present or absent.  Depending on the hair, this hollow tube is continuous, or fragmented. 

Layers of a hairA strand of hair has three layers:

1. Cuticle - the outermost covering, cuticle consists of hard overlapping, transparent cells filled with keratin protein. These cells appear like scales that point toward tips end.

 2. Cortex - contains pigment granules that give

hair its color.

3. Medulla - a hollow tube within the hair, which may be present or absent.  Depending on the hair, this hollow tube is continuous, or fragmented.

Imbricate Scales

The imbricate or flattened scales type consists of overlapping scales with narrow margins. They are commonly found in human hairs and many animal hairs.

Coronal Scales

Crown-like Scales that completely encircle the hair shaft. They have a 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.

Spinous Scales

• 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.

Medullae

•Continuous•Discontinuous or Interrupted•Fragmented or Trace•Absent

Interrupted or discontinuous

Medulla absent

Continuous

Follicular Tags

• If you pull a hair that is in anagen phase, it has a follicular tag attached to the root – this tag is very important for forensic analysis – – tells you if a hair has fallen out or pulled out – hair

pulled out usually has the follicular cells– How quickly it has been pulled out – hair pulled

quickly has the follicular cells attached

• The follicular tag is also a useful source of DNA

(Root)

Nuclear DNA from Hair

• Best source of nuclear DNA is the Follicular tag

• If absent, nuclear DNA can be retrieved from the root however, hair in anagen phase will yield more DNA than hair in other phases.

• So hairs found at a crime scene will not necessarily be good sources of nuclear DNA – unless they were pulled out.

Mitochondrial DNA

• If nuclear DNA is not found, an examiner can locate the mitochondria of the hair cells – they also contain DNA!

• Each cell has multiple copies of mitochondria, and each mitochondrion has multiple copies of DNA; so you may be able to find at least one copy.

• mtDNA is only passed from mother to child, whereas nuclear DNA is passed by both parents

Hair Color• White – lacks melanin (albinism)• Gray hair – a mix of pigmented and

unpigmented hair• Black and brown – tons of melanin• Blonds – Less melanin• Red hair – contains an extra pigment

called trichosiderin (iron based)

Goosebumps!• Smooth muscle attached to each hair follicle can

contract and cause short hairs to stand on end• These muscle bundles are called arrector pili

muscles• They appear when scared, excited, cold, etc.

Glands - Sebaceous

• Usually associated with hair follicles• Specialized epithelial cells in this gland produce

a fatty secretion that accumulates and bursts through cells

• The final product is a mix of cell debris and fatty fluid – this is called Sebum

• Sebum is secreted into hair follicles• Keeps skin and hair soft, flexible and waterproof• Too much sebum causes pores to clog and

results in acne

What can a hair tell us?

1. Part of the body from which it originated?

2. Racial origin of hair?

3. Age and sex of the hair’s owner?

4. Was it forcibly removed?

5. Can DNA help identify the owner?

Part of the body• Yes, one can determine which part of the body

the hair came from, based on the structural analysis.– Most head hair are similar to each other in diameter

and the pigment is evenly distributed throughout the shaft, unlike other body hair. They may have absent, continuous or discontinuous medullae.

– Pubic hair is short, coarse and curly and they exhibit considerable diameter variation or “buckling”. The medullae are usually present and can be discontinuous or continuous. While tapered tips are common, these hairs may also be abraded or cut.

Part of the body, cont’d.

– Beard / Mustache hairs are coarse and triangular in cross section – they have wide medullae and blunt ends due to shaving.

– Limb HairsHairs from the legs and arms constitute limb hairs. These hairs are shorter in length, arc-like in shape, and often abraded or tapered at the tips. The pigment in limb hair is generally granular in appearance, and the medulla is trace to discontinuous.

Hair from different parts of the body

Pubic hair “buckling”

• Caucasoid (European)Hairs of Caucasoid or Caucasian origin can be of fine to medium coarseness, are generally straight or wavy in appearance, and exhibit colors ranging from blonde to brown to black. The hair shafts of Caucasian hairs vary from round to oval in cross section and have fine to medium-sized, evenly distributed pigment granules.

Racial origin of hair

Mongoloid (Asian)• Hairs of Mongoloid or Asian origin

are regularly coarse, straight, and circular in cross section, with a wider diameter than the hairs of the other racial groups. The outer layer of the hair, the cuticle, is usually significantly thicker than the cuticle of Negroid and Caucasian hairs, and the medulla, or central canal, is continuous and wide. The hair shaft, or cortex, of Mongoloid hair contains pigment granules that are generally larger in size than the pigment granules of Caucasian hairs and which often appear to be grouped in patchy areas within the shaft. Mongoloid hair can have a characteristic reddish appearance as a product of its pigment.

Negroid (African)• Hairs of Negroid or African origin are

regularly curly or kinky, have a flattened cross section, and can appear curly, wavy, or coiled. Negroid pigment granules are larger than those found in Mongoloid and Caucasian hair and are grouped in clumps of different sizes and shapes. The density of the pigment in the hair shaft may be so great as to make the hair opaque. A Negroid hair shaft exhibits variation or apparent variation in diameter because of its flattened nature and the manner in which it lies on the microscope slide. Twisting of the hair shaft, known as buckling, can be present, and the hair shaft frequently splits along the length.

Age of the hair’s owner

• The age of an individual cannot be determined definitively by a microscopic examination; however, the microscopic appearance of certain human hairs, such as those of infants and elderly individuals, may provide a general indication of age. The hairs of infants, for example, are generally finer in microscopic appearance. As individuals age, hair can undergo pigment loss and changes in the configuration of the hair shaft to become much finer and more variable in diameter.

Sex of the hair’s owner

• Although the sex of an individual is difficult to determine from microscopic examination, longer, treated hairs are more frequently encountered in female individuals. Sex can be determined from a forcibly removed hair (with tissue), but this is not routinely done.

Forcibly removed

• If you pull a hair that is in anagen phase, it has a follicular tag attached to the root – this tag is very important for forensic analysis – – tells you if a hair has fallen out or pulled out – hair

pulled out usually has the follicular cells– How quickly it has been pulled out – hair pulled

quickly has the follicular cells attached

• The follicular tag is also a useful source of DNA

Hair Collection and Preservation• “Reference” hair must always be collected from the

victim of a crime as well as all suspects• About 15 hairs from all over the head, 24 from pubic

area• Entire hair length collected – pulled from root• The hair collected must be from the same body

parts, since a pubic hair found on a rape victim cannot be compared to the head hair of a suspect.

• Rape victims must have their pubic area combed for perpetrator’s hair. Comb is packaged separately

• Dead victims – hair collected during autopsy

FIBERSFIBERS

Types of Fibers

NaturalRegenerated (Fibers manufactured

from natural fibers)Man-Made

Natural fibers

• Produced by plants, animals, and geological processes. They can be classified according to their origin:– Plant fibers – made of cellulose and lignin like

cotton, jute, sisal, etc. Vegetable fiber can be used to make paper and textiles and also in food as fiber.

– Animal fibers – wool, silk, hair (cashmere, angora, mohair), sinew (tendon), gut (for string instruments)

– Mineral Fibers– asbestos is the only naturally occurring long, mineral fiber

Natural Fibers

Asbestos naturally occurring on muscovite rock

Cellulose fibers

Regenerated Fibers (Partially Synthetic)

• Cellulose from plant material is extracted and treated with or dissolved in special chemicals.

• The cellulose solution is then squeezed through small holes in a spinneret

• Examples of regenerated fibers are rayon, aAcetate, triacetate

Man-Made Fibers (Completely Synthetic)

• Mineral– Fiberglass made from specific glass formulas and

optical fiber, made from purified natural quartz, are also man-made fibers that come from natural raw materials.

– Metallic fibers can be drawn from ductile metals such as copper, gold or silver and extruded or deposited from more brittle ones such as nickel, aluminum or iron.

– Carbon fibers are often based on carbonised polymers, but the end product is pure carbon.

Man-Made Fibers(Completely Synthetic)

• Polymer – Made from petro-chemical sources or hydrocarbon origins.– Nylon– Polyesters– Acrylic– Microfiber (really fine polyester)

What is a Polymer?

• Made from repeating subunits bonded together – 1 subunit is called a monomer

1. Natural – Plant example: cellulose, starch– Animal example: Polypeptides (Proteins)

2. Man-made – example: polyester

Starch vs. Cellulose

• Plants make starch and cellulose out of glucose.

• Glucose can come in an alpha () form or beta () form

• Starch is made by linking -glucose molecules

• Cellulose is made by linking -glucose molecules

Starch vs. Cellulose

Animal Polymers

All plant and animal proteins are polymers. Examples: keratin, fibrin, collagen, etc.

Man-Made Polymers

• Polyesters, Kevlar®,

Kevlar®

Comparing a crime scene fiber to a ‘suspect’ fiber(Side-by-side comparisons)

1. Examine color and diameter of fiber using a comparison microscope

2. Determine if any length-wise striations are present on the fibers

3. Determine if any dye particles are embedded on the surface of the fiber

4. Examine shape of fiber (cross section)5. Use a microspectrophotometer to analyze dye

composition – some fabrics may look alike in color, but they are not!

6. Use TLC to separate dye pigments7. Determine chemical composition of the fiber – is it

cotton, nylon, polyester, etc.8. Determine refractive index and Becke Lines

Dye TriviaDye Trivia

• Other than blue denim fibers and pure Other than blue denim fibers and pure white cotton fibers, no two people can be white cotton fibers, no two people can be wearing identically colored fabrics.wearing identically colored fabrics.

Refractive Indices

• Light passing through a fiber will emerge polarized - parallel and perpendicular to the fiber

• Forensic scientists can determine the refractive indices of various synthetic fibers by immersing them in fluids of different refractive indices and looking for the Becke line.

• The refracted light can appear parallel, perpendicular and birefringent.

– Parallel polarization is polarization parallel to the surface– Perpendicular polarization is perpendicular to the surface– Birefringence is double refraction

Parallel polarization (polarization in the plane of incidence)

Birefringence (Double refraction)

Collecting Fiber EvidenceCollecting Fiber Evidence• Identify “carriers” of fiber evidenceIdentify “carriers” of fiber evidence• Package the evidence separately so the fibers Package the evidence separately so the fibers

do not come in contact with other articles of do not come in contact with other articles of clothing evidenceclothing evidence

• Carpets, linen, etc must be rolled, folded and Carpets, linen, etc must be rolled, folded and packaged carefullypackaged carefully

• Car seats must be wrapped in polyethylene Car seats must be wrapped in polyethylene sheetssheets

• Adhesive tape can be used to lift fiber evidence Adhesive tape can be used to lift fiber evidence from bodies and other evidence that cannot be from bodies and other evidence that cannot be taken to the crime labtaken to the crime lab

• Forceps must be used to remove a sample fiber Forceps must be used to remove a sample fiber from fabric for testingfrom fabric for testing

PAINT

What is it?

• Paint is any liquid, liquifiable, or mastic (resin/gum) composition which after application to a substrate in a thin layer is converted to an opaque solid film after the solvent evaporates.

• Paint is used for – Protection from water, UV and other damage and

corrosion– Decoration– Added functionality such as heat radiation, light

reflection, etc.

What’s in Paint?

1. Pigments – give paint its color and opacity. They can be natural (clay, silica, talc, etc.) or synthetic

2. Binders – also called resin, give paint its adhesive quality. Binders keep pigments together and also give paint its gloss, durability and flexibility. Binders can be natural like oils or synthetic like acrylic, latex, epoxy, etc.

3. Solvent – This is used to adjust the viscosity of paint. Water based paints use water and oil-based paint use organic solvents such as turpentine, glycols, acetones, etc.

4. Additives and fillers – Used to prevent bacterial growth, improve flow and surface tension and generally to improve shelf-life

Pigments

Cinnabar and Lapis Lazuli

Cinnabar is the original source of vermilion and Lapis lazuli of Prussian blue

Sources of Pigments• Arsenic pigments: Paris Green • Carbon pigments: Carbon Black, Ivory Black, Vine Black, Lamp Black • Cadmium pigments: cadmium pigments, Cadmium Green, Cadmium Red, Cadmium

Yellow, Cadmium Orange • Iron oxide pigments: Caput Mortuum, oxide red, Red Ochre, Sanguine, Venetian Red • Prussian blue • Chromium pigments: Chrome Green, Chrome Yellow • Cobalt pigments: Cobalt Blue, Cerulean Blue, Cobalt Violet, Aureolin • Lead pigments: lead white, Naples yellow, Cremnitz White, red lead • Copper pigments: Paris Green, Verdigris, Viridian, Egyptian Blue, Han Purple • Titanium pigments: Titanium White, Titanium Beige, Titanium yellow, Titanium Black • Ultramarine pigments: Ultramarine, Ultramarine Green Shade, French Ultramarine • Mercury pigments: Vermilion (from cinnabar)• Zinc pigments: Zinc White • Clay earth pigments (which are also iron oxides): Raw Sienna, Burnt Sienna, Raw

Umber, Burnt Umber, Yellow Ochre. • Lapis lazuli, • Biological origins: Alizarin, Alizarin Crimson, Gamboge, Indigo, Indian Yellow,

Cochineal Red, Tyrian Purple, Rose madder • Other Organic: Pigment Red 170, Phthalo Green, Phthalo Blue, Quinacridone

Magenta.

Automotive Paints

• Paint chips from automobiles happen to be one of the most common paint examined by forensic scientists.

• Each car manufacturer has unique paint colors and finishes.

• Car manufacturers apply many different layers to a car’s steel body during the painting process.

• This makes it far more difficult to analyze a paint chip and marry it to a particular make, model and year.

The Typical Automotive Painting Process

1. Electrocoat Primer• Made of Epoxy resin • Applied directly to the steel frame • Black or grey in color• Prevents corrosion

2. Primer Surfacer• Applied after the electrocoat primer• Epoxy polyester or polyurethane• Smoothes out any seams or imperfections in the

body• Also resists corrosion• Contains pigments that will enhance the basecoat

or colorcoat

The Typical Automotive Painting Processcont’d.

3. Basecoat or Colorcoat• Contains pigment – the car’s final color• May contain mica pigments or aluminum flakes to

give it a pearl-finish or metallic finish• Nowadays lead-based pigments have been

replaced by organic-based pigments for environmental reasons

4. Clearcoat• Final coat• Contains no pigments• Give car its gloss• Resists scratches• Made of Acrylic or polyurethane

Manual

Semi-Automated

Robotic

How do you analyze paint chips?

• Use Pyrolysis Gas Chromatography

• Pyrolysis is a technique that uses high temperature to break down a complex chemical and turn it into a gas.

• The GC then separates the molecules of gas.

Collection and Preservation of Paint Chips

• Pick up with forceps or scooped up with paper• Keep in paper with druggist folds, glass or

plastic vials• Reference samples must be collected from

damaged surface – pick a sample as close to the damage as possible – paint may be different elsewhere due to fading or repainting

• Use a clean blade or scalpel to remove a ¼ inch square

THE ENDTHE END