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
Imbricate
Pectinate
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 bulbousshaped 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
Evidence
Part 2: Fiber Evidence
Douglas W. Deedrick
Unit Chief
Trace Evidence Unit
Federal Bureau of Investigation
Washington, DC
Flax Fibers Wool Fibers
Wool fibers
Flax fibers viewed with
polarized light
Cross section of man-made fibers
Cross-sectional views
of nylon carpet fibers
as seen with a
scanning electron
microscope (SEM)
Polarized Light
Orlon
Rayon
Acetate
Nylon
ID and Comparison of ManMade 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;

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
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
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
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
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
Animal Cuticle
human head hair
cat
dog
mouse
Cortex

Made up of spindleshaped 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
1. Uniserial--small blocks
in a row
3. Vacuolated--uneven pattern
4. Lattice--circular patterns
2. Multiserial--several
rows of blocks across
5. Amorphous--without a
specific pattern
Animals
MUSKRAT
RABBIT--uniserial
RABBIT--multiserial
COW
Human Hair
Human Hair
B
Very fair
IV
Red
N
Light Brown
U
Brown-Black
Human Hair—Some Effects
A razor-cut hair
A hair with a cut tip
A hair showing
buckling
A split hair
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 bulbousshaped 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

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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

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
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


Pigments
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Consists of pigments and additives suspended
in a binder and dissolved in a suitable solvent
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

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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