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FRNSC 410: Midterm 2 (Trace Evidence (Fibers (Natural (Animal (Hair, Silk)…

- - - - Plant
      - Animal
        
        Hair
        
        Silk
      - Mineral
    - - Organic
        
        Natural Polymer
        
        Synthetic Polymer
      - Inorganic
    - - Non-Technical
        
        Clothing
        
        Household Use
        
        Ropes and cordage
      - Technical
        
        Medical and others
        
        Can be more useful to find because it is not commonly found at crime scenes
      - Common Damage
        
        Normal "wear and tear"
        
        Unraveling of hems/seams, snags, pilling and thinning of fabric prior to hole formation
        
        Tear
        
        Severance caused by pulling apart of fabric leaving ragged or irregular edges
        
        Cut
        
        severance caused by sharp-edged instrument leaving neat edges
        
        3 types
        
        Stab-cut
        
        slash-cut
        
        Scissor-cut
    - - Length significantly greater than width
    - - Staple
        
        Length limited; relatively short
        
        human, vegetable fibers
      - Filaments
        
        Fibers of indefinite length
        
        typically synthetic fibers
    - - Long textile product composed of fibers
      - Single Yarns
        
        Spun yards
        
        Twisted staple fibers
        
        Filament yarns
        
        Multifilament yarns
        
        Monofilament yarns
        
        Filaments that may be twisted
      - Folded yarns
        
        Threads in which two or more single yarns are twisted together
        
        two-ply yarns, three-ply yarns
    - - Woven
        
        Plain Weave
        
        over-under pattern (aka criss-cross)
        
        Twill Weave
        
        over under interlacing with different spacing
        
        example jeans
      - Knits
        
        Weft
        
        Warp
    - - Transference
        
        First experimental studies in 1975 by Pounds and Smalldon
        
        Many factors affect fiber transfer
        
        Factors
        
        Area of contact surface
        
        Number of contacts
        
        Repeated contacts of same areas may cause transfer of fibers back to original garment
        
        Pressure (force) of contact
        
        Harder pressure more fibers transfer
        
        Nature (coarseness) of recipient garment
        
        Smooth surfaces are poor recipients
      - Persistence
        
        Fibers generally lost rapidly
        
        Rapid initial loss of fibers
        
        Pounds and Smalldon research
        
        80% of transferred fibers lost after four hours
        
        90%=95% loss after 24 hours
        
        Other factors
        
        continued wearing of recipient garment
        
        wearing of other garments over recipient garments
        
        transferred fibers positioned on recipient garment in area more prone to contact with other surfaces
        
        force of initial contact is low
        
        longer fibers generally lost more quickly than shorter fibers
      - Recovery
        
        3 common methods
        
        Forceps
        
        removal with forceps
        
        Adhesive methods
        
        preferred method after visual examination
        
        Vacuum
        
        useful for large area
        
        major drawback material typically collected includes large volume of old material
        
        Other methods
        
        scraping
        
        debatable utility
        
        endorsed by SWGMAT
        
        Not recommended by other
        
        No longer recommended methods
        
        Shaking
        
        Brushing or combing (except in assault cases)
  - - - Formers
        
        compounds that solidify without crystallization when cooled quickly after melting
        
        SiO2 (Most commons)
      - Fluxes
        
        lowers melting temperature
        
        Na2CO3 (soda ash), K2CO3 (potash), Na2SO4 (salt cake)
      - Stabilizers
        
        impart chemical resistance and strength
        
        CaO, MgO, Al2O3
    - - Soda-line-silicate
        
        Most common
      - Borosilicate glass
      - Alumino-silicate
      - Lead-alkali-silicate
      - Silica Glass
    - - Flat glass
        
        Sheet (window) glass
        
        Tempered glass
        
        Laminated glass
        
        Headlights and light bulbs
        
        Light-sensitive glass
        
        Coated glass
      - Container Glass
        
        Bottles and containers
      - Glass Fibers
        
        Continuous filament
        
        Fiber optics
        
        Non-continuous filament
        
        Insulation
    - - Physical fit of fractured glass
      - Non-optical physical properties
  - - - Scalp, pubic, and other types
      - Trichomes
        
        "hair: on plants
      - Bristles
        
        "Hair" on insects and spiders
      - Everywhere except palms of hands, soles, lips, nipples, navel, certain genital areas, and scar tissue
      - 100,000 follicles on average scalp
      - Structure
        
        Longitudinal description
        
        Shaft
        
        Portion above skin surface
        
        Root
        
        lies in follicle
        
        Cross-sectional morphology
        
        Cuticle
        
        Cortex
        
        Medulla
    - - skin cells
    - - Pollen
      - Vegetable matter
- - - - if an electronic
  - - - Schedule I
        
        no currently accepted medical use and high potential for abuse
      - Schedule II