Forensic Science: Fundamentals & Investigations, 2e Chapter 4. All rights Reserved Cengage/NGL/South-Western 2016

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1 1 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

2 A Study f Fibers and Textiles By the end f this chapter yu will be able t: 4.1 Identify and describe cmmn weave patterns f textile samples. 4.2 Cmpare and cntrast varius types f fibers thrugh physical and chemical analysis. 4.3 Describe principal characteristics f cmmn fibers used in their identificatin. 4.4 Apply frensic science techniques t analyze fibers. 2 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

3 Vcabulary 3 amrphus crystalline direct transfer fiber mineral fiber mnmer natural fiber Frensic Science: Fundamentals & Investigatins, 2e plymer synthetic fiber secndary transfer textile warp weft yard (thread) Cengage/NGL/Suth-Western 2016

4 Intrductin Fibers are used in frensic science t create a link between crime and suspect. Fibers are a frm f trace evidence. 4 Direct transfer Secndary transfer Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

5 Intrductin Prs Cns 5 Very cmmn in envirnment Many fibers are easily shed Fibers can easily be transferred, either singularly r in a series f events Fibers must be cllected within 24 hurs, can fall ff victim r be lst frm the scene Fibers are nt specific t an individual (smetimes) Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

6 Cllecting, Sampling, and Testing Fiber Evidence 6 Fiber evidence is cllected using tape, frceps, a vacuum, r a sticky lint rller. Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

7 Evaluating Fiber Evidence The value f fiber evidence in a crime investigatin depends n its ptential uniqueness. 7 Type f fiber Fiber clr Number f fibers fund Where the fiber was fund Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

8 Evaluating Fiber Evidence (cntinued) 8 Textile frm which the fiber riginated Multiple fiber transfers Type f crime cmmitted Time between crime and discvery f fiber Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

9 Fiber and Textile Evidence Fiber Classificatin 9 Natural Fibers Synthetic (Manufactured) Fibers Semi-synthetic, which is a fiber that is made frm a naturally ccurring substance (Rayn-made frm wd pulp residue) Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

10 Cmmn Fibers 10 Natural Synthetic Semi-synthetic Cttn-plant Nyln Rayn-wd pulp Wl-sheep Plyester Linen-flax plant Olefin Silk-silkwrm Acetate Asbests-mineral Acrylic Cashmere-gat Spandex Mhair-rabbit Fiberglass Frensic Science: Fundamentals & Investigatins, 2e

11 Natural Fibers 11 Natural fibers cme frm animals, plants, and minerals that are mined frm the grund. Fibers are cmpsed f plymers, r lng, repeating mlecules. Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

12 Animal Fibers 12 Three surces f animal fibers are hair, fur, and webbing. All animal fibers are made f prteins. Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

13 Plant Fibers 13 All plant fibers share the clumn plymer cellulse. Cellulse is made up f simple glucse units. Prteins and cellulse have very different chemical and physical prperties that allw a frensic scientist t tell animal and plant fibers apart. Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

14 Natural Fibers (cntinued) Seed fibers Leaf fibers 14 Cttn is fund in the seed pd f the cttn plant. It is used extensively fr clthing and husehld textiles. Manila Sisal Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

15 Natural Fibers (cntinued) Fruit fibers Cir fiber is btained frm ccnuts 15 Stem fibers It is relatively waterprf. Frensic Science: Fundamentals & Investigatins, 2e Flax, jute, and hemp are all prduced frm the thick regin f plant stems. Cengage/NGL/Suth-Western 2016

16 Natural Fibers (cntinued) Mineral fibers 16 Neither prteins nr cellulse May nt even be lng, repeating plymers Althugh it is very durable, because f its health risks, asbests is n lnger cmmnly used. Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

17 Synthetic (Manufactured) Fibers Half f the fabrics prduced tday are synthetic fibers. 17 The fibers are prduced by jining many mnmers tgether t frm plymers. Rayn, acetate, nyln, acrylics, and plyesters Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

18 Plymers Hmplymers plymers with ne repeating unit Example: plystyrene Cplymers tw r mre mnmers Example: nyln Blck plymers cntain blcks f similar mnmers that repeat Crss-linked plymers small mlecules that attach tw strands tgether Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western

19 Synthetic (Manufactured) Fibers (cntinued) Regenerated fibers (r mdified natural fibers, usually cellulse-based) Rayn Synthetic plymer fibers (Nn-cellulse base, usually petrleum) 19 Plyester Nyln Acrylic Olefins Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

20 Cmparisn f Natural and Synthetic Fibers 20 Synthetic fibers are strnger than the strngest natural fibers. Manufactured fibers are nt damaged by micrrganisms. Manufactured fibers can deterirate in bright sunlight and melt at a lwer temperature than natural fibers. Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

21 21 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

22 Yarns 22 Fibers t shrt in their raw state t be used t make textiles may be spun tgether t make yarns. Fr identificatin purpses, frensic scientists analyze twist directin f yarn. Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

23 Textiles 23 Weaving cnsists f arranging lengthwise threads (the warp) side-by-side and clse tgether. Crss wise threads (the weft) are then wven back and frth in ne f several different patterns. Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

24 24 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

25 Textile Analysis The ways that fabrics differ include: 25 Thread cunt Weave pattern Tw ply Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

26 26 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

27 Fiber Testing Micrscpic characteristics Plarized light micrscpy FTIR PyGC 27 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

28 Fiber Micrscpy Imprtant characteristics f fiber mrphlgy Type- mst imprtant characteristic Dye staining fr fabric ID Dyed Cttn Fibers Wl Fibers Flax Under Plarized Light Size natural fibers measured in µm (micrmeters); synthetic fibers measured in denier (weight unit) Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western

29 Fiber Micrscpy Imprtant characteristics f fiber mrphlgy Crss sectin rund, bilbal r trilbal Trilbal Synthetic Fibers Clr- natural, bleached r dyed Crimp- natural wave r twist Cttn fibers Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

30 Analysis f Synthetic Fibers Micrscpy Plarized Light Depending n set-up, measuring hw much light passes thrugh fiber r hw much light reflects Delusterants added t synthetic fibers t reduce shine different manufacturers use different chemicals Frensic Science: Fundamentals & Investigatins, 2e RI1 Cengage/NGL/Suth-Western

31 Chemical Analysis f Fibers Tw majr methds fr fiber analysis: Furier Transfrm Infrared Spectrphtmetry r FTIR - nndestructive and determines class and subclass Pyrlysis Gas Chrmatgraphy r PyGC - can be used n samples as small as 1/8, but it is a destructive technique. Superir t FTIR in distinguishing clsely related fibers because it is very sensitive t small differences in chemical makeup Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western

32 Analysis f Synthetic Fibers N amunt f regular testing allws fr individualizatin f a fiber Tear Match: may be pssible t individualize fabric t surce based n tear and pattern piece f trn fabric matches surce Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western

33 Summary 33 Fibers are a frm f class evidence used by crime-scene investigatrs; they are a frm f trace evidence. Fiber evidence may be gathered using tape, frceps, a vacuum, r a sticky lint rller. Frensic scientists will try t determine the type f a fiber, its clr, hw many fibers f each kind were fund, where they were fund, what textile the fiber came frm, and whether there were transfers f multiple types f fibers. Fibers may be analyzed using plarized light micrscpy, infrared spectrscpy, burn tests, r tests fr slubility in different liquids. Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

34 Summary (cntinued) 34 Fibers may be classified as natural r synthetic. Natural fibers include animal hair; plant fibers frm seeds, fruit, stems, r leaves; and mineral fibers. Synthetic fibers include regenerated r mdified natural fibers as well as synthetic plymer fibers. Fibers are spun int yarns that have specific characteristics. Yarns are wven, with different weave patterns, int textiles. Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016