Hair and Fiber

The study of important trace evidence

www.coolphysics.org/Hair,%20Fiber,%20and%20Paints

%2005.ppt

Important Forensic Questions Can the body area from which a hair

originated be determined? Can the racial origin of hair be

determined? Can the age and sex of an individual be

determined from a hair sample? Is it possible to determine if a hair was

forcibly removed from the body? Are efforts being made to individualize

human hair? Can DNA individualize a human hair?

Morphology and Structure of Hair

Hair Morphology Con’t

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

Cuticle Types

Mosaic Pectinate

Imbricate Petal

Diamond

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

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: best if medullary index <

1/3 Animals: best if medullary index >

1/2

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 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

Identification and Comparison of Hair

No 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

Morphology: Root

Human hair grows in three developmental stages: anagen, catagen, and telogen phases

Root: Anagen Phase Initial growth phase during which hair

follicle is actively producing hair, phase may last 6 years, root is flame like in appearance

When pulled this root may contain a follicular tag (rich source of DNA)

Anagen hair root

Root w/ follicular tag

Root: Catagen Phase

A transition phase—hair grows at a decreasing rate for two to three weeks—elongated appearance as root bulb shrinks and is being pushed out of hair follicle

Catagen hair root

Root: Telogen phase

Hair growth has ended—root takes on a club-like appearance—during two-six month period, the hair will be pushed out of the follicle causing the hair to shed naturally

Telogen hair root

Important Forensic Questions Can the body area from which a hair

originated be determined? Can the racial origin of hair be

determined? Can the age and sex of an individual be

determined from a hair sample? Is it possible to determine if a hair was

forcibly removed from the body? Are efforts being made to individualize

human hair? Can DNA individualize a human hair?

Identification and Comparison of Hair (cont)

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

11 percent of all morphological hair matches are generally found to be non-matches; need DNA to augment findings

Mitochondrial DNA can be analyzed from any part of the hair

Often cost and time prohibitive; samples often contaminated

Nuclear DNA can be analyzed if hair was pulled forcefully

What can be determined Body areas:

Scalp hairs show little variation of diameter and have more uniform distribution of pigment color

Pubic hair are short, curly with a wide range of variations in shaft diameter and a continuous medulla

Beard hairs: coarse and usually triangular in cross-section with blunt tips from cutting or shaving

What can be determined Racial origin:

Can distinguish between Negroid and Caucasian head hair

Negroid hair: normally kinky, containing dense, unevenly distributed pigments

Caucasian hair: straight or wavy, with very fine to coarse pigments that are more evenly distributed when compared to Negroid hair

Cross sections of Caucasian hair are oval to round in shape

Negroid hair are flat to oval in shape

These are general in nature

What can be determined Age cannot be determined with any degree

of certainty except with infant hair Fine, short in length, have fine pigment and are

rudimentary in character Sexual discrimination at this time is not

considered to be a routine forensic technique Microscopic examination of the hair root may

establish if the hair has fallen out or has been pulled out Hair root with follicular tissue adhering to it is

indicative that the hair has been pulled out

What can be determined Microscopic examination of the hair root

may establish if the hair has fallen out or has been pulled out Hair root with follicular tissue adhering to it is

indicative that the hair has been pulled out Hair naturally falling out will have a bulbous-

shaped root free of adhering tissue It has been demonstrated that a root may be

devoid of any adhering tissue even though it was pulled out from the body

Hairs pulled out quickly are more likely to have sheath cells when compared to hairs that have been pulled out slowly

What can be determined The current approach for examination of hair

is the morphological characteristics Breakthroughs in nuclear DNA typing has

extended the technology to the individualization of human hair Examiners can link a particular human hair to an

individual by characterizing the nuclear DNA in the hair root or follicular tissue adhering to the root

Higher rate of success extracting DNA from a hair in the anagen phase or anagen hairs entering the catagen phase then those in the telogen phase

What can be determined FBI has initiated a program to compare

human head hair and pubic hair through DNA analysis Mitochondrial DNA: is found located outside

the nucleus Only transmitted from mother to child Many copies of mitochondrial DNA in cells as

compared to nuclear DNA

Collection

Crime scene hairs must always be accompanied by an adequate amount of control samples from the victim and from suspects

Hair from any one area of the body varies significantly. The questioned hairs and control hairs must come from the same area of the body

Collection Forensic hair comparisons usually involve

scalp or pubic hairs Collection of 50 full length hairs from all

areas of the scalp A minimum of two dozen full length pubic

hairs In rape cases care must be taken to first

comb the pubic area to remove all foreign hair present before the victim is sampled for control hair

Collection The entire length must be collected

because the variation of color and other morphological features extend over the entire length Accomplished by pulling the hair out of the

skin Clipping the hair at the skin line

As a matter of routine hair samples are collected from the victim(s) of a suspicious death during an autopsy

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 (see pg 207 text) Animal sources include sheep (wool), goats

(mohair, cashmere) and many other sources

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)

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

Polymers Basic chemical substance of all

synthetic fibers Consist of long chains of repeating

molecules. The repeating molecular units in the polymer are called monomers. (see pic p210)

Often referred as macromolecules or “big” molecules

Countless varieties exist

Hairs, Fibers,Crime, and EvidencePart 2: Fiber EvidenceDouglas W. DeedrickUnit ChiefTrace Evidence UnitFederal Bureau of InvestigationWashington, DC

Flax Fibers Wool Fibers

Flax fibers viewed withpolarized light

Wool fibers

Cross section of man-made fibers

Cross-sectional views of nylon carpet fibers as seen with a scanning electron microscope (SEM)

Polarized Light

Orlon

Acetate

Rayon

Nylon

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 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

Tools and Techniques to Aid in Comparing Fibers Light infrared spectrophotometer—

compares colors and chemical composition through spectral patterns

Chromatography—compares dye composition

Refraction—ID’s fiber by refractive index Comparison microscope—reveals shape,

coloring, pitting and striations

Techniques SEM Cast of its surface Casts were made of

the hairs using clear nail polish, in order to provide optimum study preparation; the contrast and definition are both greatly improved

Identification and Comparison Establish if the hair is human or animal Compare if the hair retrieved at the

crime scene is compatible from a known hair of a particular individual

The ability to distinguish human from animal is easy when compared to that of human hair comparison Various morphological characteristics

between individuals and the same individual

Identification and Comparison Microscopic examination

Animal or human Species of animal

Important characteristics: Scale structure Medullary index Medullary shape

Identification and Comparison Scalp hair Pubic hair

Comparison microscope Hair from any part of the body

exhibits a wide range of characteristics the examiner must have an adequate number of known hair samples that are representative of all its features

Identification and Comparison Compare

Length Color Diameter Presence or absence of medulla Distribution, shape and color intensity

of the pigment granules present in the cortex

Dyed, bleached or natural hair

Identification and Comparison

Dyed hair: dye color found in cuticle as well as throughout cortex

Bleaching: removes pigment from the hair and gives a yellowish tint

If there has been growth of hair since last bleach or dye treatment: natural-end will be distinct in color

Hair is known to grow at an approximate rate of 1 cm/month Therefore can estimate the time since last appointment

or treatment

Identification and Comparison

Morphological abnormalities; Diseases Deficiencies

Fungal and nit infections Class evidence If one human head hair taken from the crime scene is

found to be similar to a representative hair from a suspect’s head, the odds against it from originating from another person are about 4500 to 1

The odds of two different pubic hairs originating from two different individuals is 800 to 1

Identification and Comparison Mongoloid and Negroid hairs

exhibit less variations in many characteristics

Hair Morphology

Hair Morphology

Not possible to individualize a human hair to any single head or body

Color and structure (morphology) is the most characteristic forensic features

The shaft is composed of three layers Cuticle Cortex Medulla

Hair Morphology

Cuticle Hair is a good subject for

establishing individual identity do to: Resistance to chemical

decomposition Retain its structural features

over a long period of time This resistance and stability

is contributed to the cuticle

Cuticle

Formed by overlapping scales that always point to the tip of each hair

Scales formed formed from specialized cells that have keratinized and flattened in progressing from the follicle

Shingles of a roof Variety of patterns useful for

species identification

human head hairhuman head hair cat cat dog dog mousemouse

Animal Cuticle

Cortex Made up of spindle-

shaped cortical cells Aligned in a regular

array Parallel to the length

of the hair Imbedded with

pigment granules Granules provide

points of comparison between different individuals

Hair Taxonomy

Medulla

Collection of cells that have the appearance of a central canal

Usually most predominant feature

Medullary index: Measures diameter of

medulla relative to diameter of the hair shaft

Expressed as a fraction Humans 1/3 Most other animals 1/2

Medulla

Medulla vary between individuals

Vary between hairs of the same individual

Some hairs have no medulla

Medulla

Classified as: Interrupted Fragmented Absent Continuous

Human head hairs No medulla Fragment Mongoloid race shows

continuous

Medulla

Animals Continuous Interrupted

Arrangements

2. Multiserial--several rows of blocks across

1. Uniserial--small blocks in a row

3. Vacuolated--uneven pattern

4. Lattice--circular patterns

5. Amorphous--without a specific pattern

AnimalsMUSKRAT

COW

RABBIT--uniserial

RABBIT--multiserial

Human Hair

IVRed

UBrown-Black

NLight Brown

BVery fair

Human Hair

A razor-cut hair A hair with a cut tip

A split hair

A hair showing buckling

Human Hair—Some Effects

Root

Root and surrounding cells in the hair follicle provide for: Production of hair Continued growth

Human hair grows in three phases The shape and size of the hair root

is dependent on the phase of development

Phases

1) Anagen - Growth Phase 2) Catagen - Transitional phase 3) Telogen - Resting Phase

Anagen Phase

Approximately 85% of all hairs are in the growing phase at any one time. The anagen phase or growth phase can vary from two to six years. Hair grows approximately 10cm per year and any individual hair is unlikely to grow more than one meter long

Anagen Phase

Flame-shaped appearance of the root bulb

When pulled from the root Contain a follicular

tag Individualization of

hair DNA

Catagen Phase At the end of the

anagen phase the hairs enters into a catagen phase which lasts about two or three weeks

During the catagen phase the hair follicle shrinks to about 1/6 of the normal length. The lower part is destroyed and the dermal papilla breaks away to rest below

Catagen Phase Roots typically

take on an elongated appearance

Root bulb shrinks in size

Being pushed out of the follicle

Telogen Phase The resting phase

follows the catagen phase and normally lasts about 2-6-months. During this time the hair does not grow but stays attached to the follicle while the dermal papilla stays in a resting phase below. Approximately 10-15 percent of all hairs are in this phase at an one time.

Telogen Phase At the end of the

telogen phase the hair follicle re-enters the Anagen phase. The dermal papilla and the base of the follicle join together again and a new hair begins to form. If the old hair has not already been shed the new hair pushes the old one out and the growth cycle starts all over again

What can be determined Body areas:

Scalp hairs show little variation of diameter and have more uniform distribution of pigment color

Pubic hair are short, curly with a wide range of variations in shaft diameter and a continuous medulla

Beard hairs: coarse and usually triangular in cross-section with blunt tips from cutting or shaving

What can be determined Racial origin:

Can distinguish between Negroid and Caucasian head hair

Negroid hair: normally kinky, containing dense, unevenly distributed pigments

Caucasian hair: straight or wavy, with very fine to coarse pigments that are more evenly distributed when compared to Negroid hair

Cross sections of Caucasian hair are oval to round in shape

Negroid hair are flat to oval in shape

These are general in nature

What can be determined Age cannot be determined with any degree

of certainty except with infant hair Fine, short in length, have fine pigment and are

rudimentary in character Sexual discrimination at this time is not

considered to be a routine forensic technique Microscopic examination of the hair root may

establish if the hair has fallen out or has been pulled out Hair root with follicular tissue adhering to it is

indicative that the hair has been pulled out

What can be determined Microscopic examination of the hair root

may establish if the hair has fallen out or has been pulled out Hair root with follicular tissue adhering to it is

indicative that the hair has been pulled out Hair naturally falling out will have a bulbous-

shaped root free of adhering tissue It has been demonstrated that a root may be

devoid of any adhering tissue even though it was pulled out from the body

Hairs pulled out quickly are more likely to have sheath cells when compared to hairs that have been pulled out slowly

What can be determined The current approach for examination of hair

is the morphological characteristics Breakthroughs in nuclear DNA typing has

extended the technology to the individualization of human hair Examiners can link a particular human hair to an

individual by characterizing the nuclear DNA in the hair root or follicular tissue adhering to the root

Higher rate of success extracting DNA from a hair in the anagen phase or anagen hairs entering the catagen phase then those in the telogen phase

What can be determined FBI has initiated a program to compare

human head hair and pubic hair through DNA analysis Mitochondrial DNA: is found located outside

the nucleus Only transmitted from mother to child Many copies of mitochondrial DNA in cells as

compared to nuclear DNA

Collection

Crime scene hairs must always be accompanied by an adequate amount of control samples from the victim and from suspects

Hair from any one area of the body varies significantly. The questioned hairs and control hairs must come from the same area of the body

Collection Forensic hair comparisons usually involve

scalp or pubic hairs Collection of 50 full length hairs from all

areas of the scalp A minimum of two dozen full length pubic

hairs In rape cases care must be taken to first

comb the pubic area to remove all foreign hair present before the victim is sampled for control hair

Collection The entire length must be collected

because the variation of color and other morphological features extend over the entire length Accomplished by pulling the hair out of the

skin Clipping the hair at the skin line

As a matter of routine hair samples are collected from the victim(s) of a suspicious death during an autopsy

Types of Fibers

Fibers comprise our fabrics and garments Important evidence in incidents that involve

personal contact Homicide Assault Sexual offenses

The force of impact between a hit-and-run victim and vehicle

Fibers Threads Clothing pieces

Breaking-and-entering Fibers can adhere to broken glass and

screens

The development of fibers, fabrics, finishes, and other textile-processing techniques has made greater advances since the 1900’s than the four-five thousand years of recorded history

Types of Fibers Natural fibers

Animals Wool -sheep Mohair, cashmere - goats Camels Llamas Alpacas Vicunas Fur fibers- mink, rabbit, beaver, and muskrat

Identification and comparison will rely solely on color and morphological features viewed with the microscope

Types of Fibers Plant fiber

Cotton- most prevalent Wide use of undyed cotton fibers in

clothing and other fabrics: This evidence is meaningless

Dyed cotton in a combination of colors: some cases used to enhance its evidential significance

Microscopic distinguishing feature: ribbonlike shape with twists at irregular intervals

Man-Made Fibers 1911 Rayon 1920’s Cellulose acetate 1939 Nylon Increasing replacing natural fibers Fibers are marketed under trademark

names,so to avoid confusion, the U.S. Federal Trade Commission has approved “generic” or family names for the grouping of all man-made fibers

Polyesters U.S.

DacronR, FortrelR, KodelR

England TeryleneR

First machine-made fibers derived from cotton or wood pulp

Regenerated fibers: Raw materials from cotton or wood pulp Processed Pure cellulose is extracted Type of fiber desired, the cellulose is

chemically treated and dissolved in solvent Forced through the small holes of a spinning

jet or spinneret Rayon, acetate, triacetate: Regenerated

cellulose

Synthetic fibers: produced solely from synthetic chemicals Nylons Polyesters Acrylics

Creation of synthetic fibers came about when scientist developed the method of synthesizing long-chained molecules (polymers)

Glass rod in placed in a beaker in contact with viscous material

Slowly pull glass rod away Substance adheres to rod Forms a fine filament Hardened as soon as it enters cool

air Cold filaments could be stretched

several times their extended length Flexible, strong, attractive fiber

Nylon first synthetic approved fiber

Polymer is the basic chemical substance of all polymers Plastics Paints Adhesives Synthetic rubber Can be made to assume different

chemical and physical properties Chemical substances are

composed of the molecule, the basic structural unit H2O

Heroin: C21H23O5N Polymers are formed by linking

together a large number of molecules: macromolecules

Resembles a long repeating chain Monomers are the repeating

molecular units Varying the chemical structure of

the monomers and devising numerous ways of weaving them together Polymers that exhibit different

properties

This versatility enables the synthesis of:

Glues Plastics Paints Fibers

In nature these chemical principles produce hair and vegetable fibers

Cellulose, the basic ingredient of wood and cotton and Starch are both natural polymers made up of carbohydrate molecules

Polarized Light Microscopy Digital Image Gallery

http://microscopy.fsu.edu/primer/techniques/polarized/gallery/pages/orlonsmall.html

If presented with fibers that can exactly be fitted together at the torn edges: common origin of fabric

Usually fibers must be viewed at a side by side comparison Microscopic examination for color Microscopic examination for diameter Lengthwise striations on the surface Pitting of fiber’s surface with delustering

particles (titanium dioxide) Shape of fiber through cross-sectional

view

Fig. 2. SEM image at 10000 magnification and 20 kV of titania coated nylon-6 nanofibers obtained through the sol gel coating technique. The average diameter of the fibers is about 150 - 200 nm.

Dyed fibers can look the same but their composition may be different

Visible light microspectrophotometer compares the colors of fibers through special patterns

More detail: chromatographic separation These tests are performed to show the

fibers belong in the same generic class Can be enhanced if it shows that the

fibers belong to the same subclassification within their generic class

Nylon 6, Nylon 6-10, Nylon 11, and Nylon 6-6 May differ in physical shape Differ appearance Differ in dyeability Do to modifications in basic chemical structure

Many manufactured fibers exhibit birefringence The regular arrangement of the fiber,s

polymers cause crystallinity in the finished fiber

The crystallinity; Strength Stiff Optical property of double refraction

Infrared spectrometry Rapid and reliable method for identifying

generic class and in some instances the subclass

Collection This evidence will usually not be seen by the

naked eye Identify and preserve potential “carriers” of

fiber evidence Packaged separately in paper bags Some articles must not be placed on the same

surface prior to packaging Carpets, rugs, and bedding: folded carefully to

protect areas suspected of having fiber evidence Car seats: covered with polyethylene sheets Adhesive tape lifts of exposed body areas of

victim

Forensic Examination of Paint

One of the most prevalent forms of physical evidence

Perhaps most frequently encountered in hit-and-run and burglary cases

Small quantities of paint recovered from an accident scene Color, make, and model of automobile

Paint on a surface will dry into a hard film Consists of pigments and additives

suspended in a binder and dissolved in a suitable solvent

Pigments Color Opacity Usually mixtures of different inorganic and

organic compounds Binder

Support medium Polymeric substance

Automobile paint: Manufacturers apply any number of coatings to

the automobile’s body Automobile finishing system for steel:

Electrocoat primer: epoxy-based resins Electroplated to prevent corrosion Uniform in appearance Colors range from gray to black

Primer surface: epoxy-modified polyesters Function is to completely smooth out and hide seams

and imperfections Highly pigmented: color pigments are used to minimize

color contrast between primer and topcoats

Automobile finishing system for steel: Basecoat or colorcoat: The binder is most

commonly made up of an acrylic-based polymer Provides color and aesthetics (Eye appeal) The layers integrity is dependent on the ability

to resist the elements Use of lead , chrome, and other heavy metals

has been abandoned Organic-based pigments Trend towards pearl luster or mica pigments

(coated with a metal oxide) Aluminum flakes imparts a metallic look

Clearcoat: acrylic-based or polyurethane Provides etch resistance Appearance Improves gloss and durability

Microscope has been traditionally used for locating and comparing paint specimens Compared side by side by a stereoscopic

microscope for: Color Surface Texture Color layer sequence

Paint specimens possess colored layers When they match with respect to number

and sequence of colors it can be said the two paint specimens are from the same origin

The diverse chemical composition of today's modern paints provides for additional points of comparison Wide variation in binder formulations

Significant information with respect to automobile finishes

The knowledge that paint manufacturers make hundreds of finishes is most helpful when examining a paint specimen

Pyrolysis gas chromatography: invaluable Pyrogram: this pyrogram distinguishes one

polymer from another in the binder

Infrared spectrophotometry: analysis of binder composition

Binders will actively absorb infrared radiation to yield a highly characteristic spectrum

The elements that comprise the inorganic pigments can be identified by Emission spectroscopy Neutron activation analysis X-ray diffraction X-ray spectroscopy

The emission spectrograph can simultaneously detect 15-20 elements in most automobile paints

If compared by layer structure, solvent tests, pyrolysis gas chromatography and X-ray spectroscopy the chances of a paint chip from a crime scene matching a randomly chosen vehicle is 16,000 to 1

Starting with the 1974 model year,The Law Enforcement Standards Laboratory at the National Bureau of Standards collected and disseminated to crime labs auto paint color samples

PDQ (Paint Data Query): database put together by the Royal Canadian Mounted Police Forensic Laboratory

Allows for the obtaining of information on paints related to automobile make, model, and year.

Parameters Automotive paint layer colors Primer colors Binder composition

Collection and Preservation

Picked up with tweezers Scooped up with a piece of paper Paper druggist folds Glass or plastic vials If paint is embedded or smeared in

garments or objects, the objects or garments are packaged

Collection and Preservation

Uncontaminated control samples must always be taken from an undamaged area as close to the damaged area as possible

Removal accomplished by using a clean scalpel or knife blade to include all the paint layers 1/4 inch square