Hairs, Fibers, and Paint Criminalistics Chapter 8.
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Transcript of Hairs, Fibers, and Paint Criminalistics Chapter 8.
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Hairs, Fibers, and PaintHairs, Fibers, and Paint
CriminalisticsCriminalistics
Chapter 8Chapter 8
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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
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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
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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
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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.
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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.
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The Hair Shaft: 4 PartsThe Hair Shaft: 4 Parts
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
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The Hair Shaft: 4 PartsThe Hair Shaft: 4 Parts
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
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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.
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Medulla ExamplesMedulla Examples
Photomicrograph of Animal Hair with vacuolated medullae.
Photomicrograph of Deer Medulla with lattice-shaped medulla.
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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
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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
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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
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The Hair Shaft: 4 PartsThe Hair Shaft: 4 Parts
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
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Phases of Root GrowthPhases of Root Growth
Flame-Shaped Root
Elongated Root Club-Shaped Root
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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
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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
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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
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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.
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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
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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
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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
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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
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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
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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
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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
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Collection and PreservationCollection and PreservationOf Hair EvidenceOf Hair Evidence
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
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Collection and PreservationCollection and PreservationOf Hair EvidenceOf Hair Evidence
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
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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
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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
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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
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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
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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
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Identification and Identification and Comparison of Man-Made Comparison of Man-Made
FibersFibers
Dye comparison using a Dye comparison using a microspectrophotometermicrospectrophotometer
NotNot limited by size of sample limited by size of sample
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Identification and Identification and Comparison of Man-Made Comparison of Man-Made
FibersFibers ChromatographyChromatography
Separate Separate shadesshades of color on a of color on a chromatographchromatograph
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Identification and Identification and Comparison of Man-Made Comparison of Man-Made
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
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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
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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
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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
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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
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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.
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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
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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
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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
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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
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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