FORENSICSCIENCETraceEvidence法医学物证

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1、FORENSICSCIENCETraceEvidence1IntroductionTraceEvidence--anysmallpiecesofmaterial,man-madeornaturallyoccurringMostcommonexamples:HairFiber2TestQuestionsforTraceEvidenceWhatisit?Isitman-madeornatural?Whatisitssource?Howcommonisit?Canitbeidentifiedtoasi

2、nglesource?3HairHumanhairisoneofthemostfrequentlyfoundpiecesofevidenceatthesceneofaviolentcrime.Itcanprovidealinkbetweenthecriminalandtheact.Fromhaironecandetermine:HumanoranimalRaceOriginMannerinwhichhairwasremovedTreatedhairDrugsingested4DNAThehairsh

3、aftcontainsabundantmitochondrialDNA--inheritedonlyfromourmothers.ItcanbetypedbycomparingrelativesifnoDNAfromthebodyisavailable.OnlytherootcontainsnuclearDNA.5HairMorphologyTheStudyofStructureandFormPartsofthehairShaft--partofthehairthatsticksoutofthesk

4、inRoot--liesbelowtheepidermisFollicle--structurefromwhichthehairgrows6HairGrowthTerminologyAnagen--hairthatisgrowingCatagen--hairatrestTelogen--hairthatisdyingLength--00.5mmperdayor1centimeterpermonth;approximatelyonehalfinchpermonth7HairCuticleMosaicP

5、ectinateImbricatePetalDiamondpetalChevronThecuticleistheoutermostlayerofhairwhichiscoveredwithscales.Scalesalsoalwayspointtowardthetipofthehair.Thesescalesdifferbetweenspeciesofanimalsandarenamesbasedontheirappearance.Someofthesescalesarevariationsofth

6、esameandinclude:8ScaleTypesMosaicChevron9ScaleTypes(cont)PectinateImbricate10ScaleTypes(cont)PetalDiamondPetal11HUMANSCALESInordertovisualizethescalespaintfingernailpolishonaslideplaceahaironthepolishliftoffthehairandobservethescaleimprintsWhatpatterni

7、sseeninthisslide?12HairCortexThecortexgivesthehairitsshape.Ithastwomajorcharacteristics:Melanin--pigmentgranulesthatgivehairitscolorCorticalfusi--airspaces,usuallyfoundneartherootbutmaybefoundthroughoutthehairshaft13Themedullaisthehaircorethatisnotalwa

8、yspresent.Themedullacomesindifferenttypesandpatterns.Types:ContinuousIntermittentorinterruptedFragmentedAbsent--notpresentHairMedulla14HairMedullaPatternsUniserialMultiserialVacuolatedLatticeAmorphous(withoutadistinctpattern)15HUMANMEDU