Hairs, Fibers, and Paint Criminalistics Chapter 8

Hairs, Fibers, and PaintHairs, Fibers, and Paint

CriminalisticsCriminalistics

Chapter 8Chapter 8

HairHair A good A good indicatorindicator of of

individualindividual identity identity Resistant to Resistant to

chemical chemical decompositiondecomposition

Retains Retains structuralstructural features over timefeatures over time

Hair is Hair is notnot an an absoluteabsolute indicator of indicator of identity but can be a identity but can be a good indicator of good indicator of identityidentity

Morphology of HairMorphology of Hair Appendage of the Appendage of the skinskin

that grows out of a that grows out of a hair hair folliclefollicle

Begins at the Begins at the hair roothair root embedded in the follicle embedded in the follicle and extends outward into and extends outward into the the shaftshaft and ends at the and ends at the tiptip

The The hair shafthair shaft is most is most commonly tested by commonly tested by forensic scientistsforensic scientists

The Hair Shaft: 4 PartsThe Hair Shaft: 4 Parts

The The cuticlecuticle: : outsideoutside covering of haircovering of hair Covered in scales that Covered in scales that

point point towardtoward the tip the tip Scales are used in Scales are used in

identification of the hairidentification of the hair Animal V. Human HairAnimal V. Human Hair

Coronal “Crown Shaped” ScalesCoronal “Crown Shaped” Scales

Spinous “Spiny” ScalesSpinous “Spiny” ScalesImbricate “Flattened” ScalesImbricate “Flattened” Scales

Cuticle PhotographsCuticle Photographs

The cuticle is a translucent outer layer of the hair shaft consisting of scales that cover the shaft.

This photograph illustrates how the cuticular scales always point from the proximal or root end of the hair to the distal or tip end of the hair.

Cuticle PhotographsCuticle Photographs

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.

Photomicrograph of the proximal scale pattern in mink 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.


The The cortexcortex: : insideinside the protective layer of the protective layer of cuticlecuticle Made of cells that are aligned Made of cells that are aligned parallelparallel to the to the

length of the hairlength of the hair PigmentPigment granules that provide granules that provide colorcolor are are

found in the cortexfound in the cortex


The The medullamedulla: found in the : found in the center center of the of the hairhair PredominantPredominant feature of hair feature of hair Can be Can be continuouscontinuous, , interruptedinterrupted, or , or

fragmentedfragmented Can be different Can be different shapesshapes in cross-section and in cross-section and

can be searched using a can be searched using a databasedatabase

Medulla ExamplesMedulla ExamplesIn human hairs, the medulla is generally amorphous in appearance, whereas in animal hairs, its structure is frequently very regular and well defined.

Photomicrograph of Uniserial Ladder Medulla Photomicrograph of Multiserial Ladder Medulla

The above examples have a well-defined appearance and

came from a rabbit.

Medulla ExamplesMedulla Examples

Photomicrograph of Animal Hair with vacuolated medullae.

Photomicrograph of Deer Medulla with lattice-shaped medulla.

When the medulla is present in human hairs, its structure can be described as—fragmentary or trace, discontinuous or broken, or continuous. This figure is a diagram depicting the three basic medullary types.

Human Medulla ExamplesHuman Medulla Examples

Discontinuous Medulla in Human Hair

Hair IdentificationAnimal Versus Human Hairs

Human hairs are distinguishable from hairs of other mammals. Animal hairs are classified into the following three basic types.

Guard hairs that form the outer coat of an animal and provide protection

Fur or wool hairs that form the inner coat of an animal and provide insulation

Tactile hairs (whiskers) that are found on the head of animals provide sensory functions

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 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.

Hair IdentificationAnimal Versus Human Hairs


The The rootroot: provides for : provides for growthgrowth of old and of old and new hairnew hair Three phases of hair growth:Three phases of hair growth:

AnagenAnagen (up to 6 yrs): root attached to follicle for (up to 6 yrs): root attached to follicle for continued growth; root bulb is continued growth; root bulb is flame-shapedflame-shaped

CatagenCatagen (2-3 weeks): slowed growth; root bulb (2-3 weeks): slowed growth; root bulb has an has an elongatedelongated appearance appearance

TelogenTelogen (2-6 months): hair growth ends and is (2-6 months): hair growth ends and is shed; root bulb is shed; root bulb is club-shapedclub-shaped

Phases of Root GrowthPhases of Root Growth

Flame-Shaped Root

Elongated Root Club-Shaped Root

Identification and Identification and Comparison of HairComparison of Hair

Most comparisons are human v. animalMost comparisons are human v. animal Human-human comparisons are Human-human comparisons are

problematicproblematic Variable Variable morphologicalmorphological characteristics characteristics VaryVary from person to person from person to person Vary within a Vary within a single individualsingle individual

Hair ComparisonHair Comparison

Use a Use a comparisoncomparison microscope microscope Compare with Compare with standard/referencestandard/reference

samplessamples Try to match Try to match colorcolor, length, and , length, and diameterdiameter

Can determine dyed or Can determine dyed or bleachedbleached hair from hair from naturalnatural

TimeTime since coloring can be determined since coloring can be determined because hair grows because hair grows ~1cm~1cm per month per month

Hair ComparisonHair ComparisonPigment granules are small, dark, and solid structures that are granular in appearance. They vary in color, size, and distribution in a single hair. In humans, pigment granules are commonly distributed toward the cuticle as shown in Figure 1, except in red-haired individuals as in Figure 2. Animal hairs have the pigment granules commonly distributed toward the medulla, as shown in Figure 3.

Figure 1 Figure 2

Figure 3

Human Hair IdentificationHuman Hair IdentificationHuman hair can be identified by racial origin, body area and other classifying techniques.

Key characteristics serve as racial indicators.

These indicators are generalities and apply primarily to head hairs.

The examiner may encounter hairs that cannot easily be associated with a particular racial model because of poorly defined characteristics, limited size, or inconsistent indicators. These hairs can be identified as apparent racial mixtures or as not classifiable.

Shaft diameter: moderate with minimal variation (mean diameter for human head hairs - 80um)

Pigment granules: sparse to moderately dense with fairly even distribution

Cross-sectional shape: oval

Caucasian Hair IdentificationCaucasian Hair Identification

Photomicrograph of Caucasian

Head Hair

Photomicrograph of Cross-section of Caucasian Hair

Negroid Hair IdentificationNegroid Hair IdentificationShaft diameter: moderate to fine with considerable variation

Pigment granules: densely distributed (hair shaft may be opaque) and arranged in prominent clumps

Shaft: prominent twist and curl

Cross-sectional shape: flattened Photomicrograph of Negroid Head Hair

Photomicrograph of Cross-section of Negroid Hair

Mongoloid Hair IdentificationMongoloid Hair IdentificationShaft diameter: coarse and usually with little or no variation

Pigment granules: densely distributed and often arranged in large patchy areas or streaks

Medulla: prominent (often broad and continuous)

Cuticle: thick

Cross-sectional shape: round

Photomicrograph of Mongoloid Head Hair

Photomicrograph of Cross-section of Mongoloid Hair

Hair ComparisonHair Comparison

Highly Highly subjectivesubjective comparative test comparative test

DNA analysisDNA analysis of hair is a much more of hair is a much more reliable testing techniquereliable testing technique

Individualizing Human Individualizing Human HairHair

NuclearNuclear DNA Analysis: DNA Analysis: DNA found in the DNA found in the nucleusnucleus of the cell of the cell

Must have Must have follicular tagfollicular tag or or rootroot structure structure present to testpresent to test

Individualizing Human Individualizing Human HairHair

MitochondrialMitochondrial DNA Analysis: DNA Analysis: DNA found in cellular material DNA found in cellular material outsideoutside of the of the

nucleusnucleus Can be tested Can be tested withoutwithout follicle or root follicle or root

structurestructure MoreMore copies of mitochondrial DNA in cells copies of mitochondrial DNA in cells

Collection and PreservationCollection and PreservationOf Hair EvidenceOf Hair Evidence

Must be submitted with an adequate sample Must be submitted with an adequate sample of hair from the of hair from the victimvictim of a crime, those of a crime, those entering a crime scene, or a entering a crime scene, or a suspectsuspect

Hair samples must be obtained from the Hair samples must be obtained from the samesame parts of the body parts of the body

Usually involve Usually involve headhead or or pubicpubic hair hair


HeadHead hair: approximately hair: approximately 5050 full-length full-length hairs neededhairs needed

PubicPubic hair: approximately hair: approximately 2525 hairs hairs neededneeded

In rape cases, area must be combed for In rape cases, area must be combed for hair hair transfertransfer and then packaged in a and then packaged in a separate separate envelopeenvelope


Hair must be Hair must be pulledpulled out of the skin or by out of the skin or by clipping it at the clipping it at the skin lineskin line

Hair is collected from the victims of Hair is collected from the victims of suspicioussuspicious deaths at deaths at autopsyautopsy

FibersFibers

Comprise our Comprise our fabricsfabrics and and garmentsgarments Important evidence in incidences that Important evidence in incidences that

involve involve personalpersonal contact contact

Homicides, assaults, & sexual Homicides, assaults, & sexual offensesoffenses

Can also be Can also be transferredtransferred in hit-and-run cases in hit-and-run cases

Problems with Fiber Problems with Fiber AnalysisAnalysis

MassMass production of garments and fabrics production of garments and fabrics has limited finding has limited finding originorigin points points

It is very It is very unusualunusual to identify fiber to identify fiber evidence with a high evidence with a high degreedegree of certainty of certainty

Natural FibersNatural Fibers Derived in whole Derived in whole

from from animalanimal or or plantplant sourcessources Animal sources: Animal sources:

sheep, goats, camels, sheep, goats, camels, llamas, alpacas, mink, llamas, alpacas, mink, rabbit, beaver, and rabbit, beaver, and muskratmuskrat

Plant sources: Plant sources: primary sourceprimary source CottonCotton

Wool Fibers

Cotton Fibers

Man-Made Man-Made FibersFibers

Derived from either Derived from either naturalnatural or or syntheticsynthetic polymerspolymers

Most have Most have distinguishable cross-distinguishable cross-sectional patternssectional patterns

Examples: Rayon, Examples: Rayon, Nylon, Acrylic, Nylon, Acrylic, Polyester, and Polyester, and SpandexSpandex Cross-Sectional Patterns of Man-Made

Fibers

Identification and Identification and Comparison of Man-Made Comparison of Man-Made

FibersFibers

Microscopic comparison using a Microscopic comparison using a comparisoncomparison microscope microscope ColorColor and and DiameterDiameter Striations and Striations and PittingPitting Shape of Fiber in Shape of Fiber in Cross-SectionCross-Section


FibersFibers

Dye comparison using a Dye comparison using a microspectrophotometermicrospectrophotometer

NotNot limited by size of sample limited by size of sample


FibersFibers ChromatographyChromatography

Separate Separate shadesshades of color on a of color on a chromatographchromatograph


FibersFibers Test Test chemicalchemical composition composition

Fibers are separated into Fibers are separated into classesclasses

LightLight Analysis Analysis Light passing through a fiber will be Light passing through a fiber will be

polarizedpolarized and have a specific index of and have a specific index of refractionrefraction

Refraction indexesRefraction indexes can be compared can be compared

Problems with Fiber IDProblems with Fiber ID

Fiber strands Fiber strands cannotcannot be linked with any be linked with any certaintycertainty to any to any singlesingle garment or origin garment or origin

Due to mass production of clothing, carpets, Due to mass production of clothing, carpets, and other fiber sourcesand other fiber sources

Importance of Fiber Importance of Fiber EvidenceEvidence

CircumstancesCircumstances of the case of the case Other evidence that may Other evidence that may linklink the suspect the suspect

to the sceneto the scene LocationLocation, number, and , number, and naturenature of fibers of fibers

examinedexamined JudgmentJudgment of the of the experiencedexperienced examiner examiner

Collection and Preservation Collection and Preservation of Fiber Evidenceof Fiber Evidence

Fiber evidence often Fiber evidence often cannotcannot be seen with be seen with the the nakednaked eye eye

Fiber evidence can be associated with Fiber evidence can be associated with any typeany type of crime and items must be of crime and items must be packaged separatelypackaged separately

Packaging of Fiber Packaging of Fiber EvidenceEvidence

Articles of clothing must be packaged Articles of clothing must be packaged separatelyseparately in in paperpaper bags bags

Carpets, rugs, and bedding must be Carpets, rugs, and bedding must be foldedfolded carefully to preserve fiber carefully to preserve fiber evidenceevidence

Car seats must be covered in Car seats must be covered in plasticplastic sheetssheets

Knife blades should be Knife blades should be covered covered to protect to protect fibers that may be fibers that may be stuckstuck to them to them

Packaging of Fiber Packaging of Fiber EvidenceEvidence

If fibers are to be removed from evidence If fibers are to be removed from evidence before it goes to the lab:before it goes to the lab: The possibility exists that the evidence The possibility exists that the evidence

would be would be lostlost in moving it from the crime in moving it from the crime scenescene

Clean Clean forcepsforceps must be used and the must be used and the evidence evidence doubledouble enveloped. enveloped.

Paint EvidencePaint Evidence

Used in Used in hit-and-runhit-and-run and and burglaryburglary cases cases

Often Often twotwo or more samples are examined or more samples are examined to determine a common originto determine a common origin

Automobile Paint Automobile Paint LayeringLayering

First Layer: First Layer: Electrocoat PrimerElectrocoat Primer Provides Provides corrosioncorrosion resistance to steel resistance to steel

Second Layer: Second Layer: Primer SurfacerPrimer Surfacer Hides any seams or Hides any seams or imperfectionsimperfections in the in the

automobile’s bodyautomobile’s body

Third Layer: Third Layer: BasecoatBasecoat ColorColor of the automobile of the automobile

Fourth Layer: Fourth Layer: ClearcoatClearcoat Improves Improves glossgloss, durability, and appearance, durability, and appearance

Examination of PaintExamination of Paint

Basecoat (Basecoat (color layercolor layer) ) provides the most provides the most evidence because of evidence because of paint paint chemical chemical compositioncomposition

LayeringLayering of paint also of paint also helps forensic helps forensic scientists determine a scientists determine a common point of origincommon point of origin

Value of Paint Value of Paint ExaminationExamination

Chemical compositionChemical composition of different paints of different paints can be linked to different can be linked to different makesmakes and and modelsmodels of automobiles and can assist in of automobiles and can assist in locating a locating a suspectsuspect vehicle vehicle

Collection and Preservation Collection and Preservation of Paint Evidenceof Paint Evidence

Loose paint chips can be Loose paint chips can be picked up with picked up with forcepsforceps and and placed in placed in envelopesenvelopes or or tight-lidtight-lid containers containers

Reference samples must Reference samples must be taken in an area be taken in an area adjacentadjacent to the missing to the missing paint chip by using a paint chip by using a scalpelscalpel or or razor bladerazor blade

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Hairs, Fibers, and Paint Criminalistics Chapter 8