Microscopic Trace Evidence - Fiber & paint Flashcards
fibers are a common class of
microscopic evidence
numerous major classifications and generic subtypes are ?
-physically different, processed many ways, transfer easily, have significant persistence and thus are valuable forensic evidence
natural fibers are derived in whole from ? or plant sources
examples
animal
wool, mohair, cashmere, furs, and cotton
man-made fibers are ?
manufactured
what man-made fibers are manufactured?
-regenerated fibers are manufactured from natural raw materials and include rayon, acetate, and triacetate
-synthetic fibers are produced solely from synthetic chemicals and include nylons, polyesters, and acrylics
what microscope is fiber analyzed under and what is documented?
-stereo microscope
size, crimp, color, luster, possible cross section, damage, soil, and adhering debris
what does the quality of the fiber evidence depend on?
the ability of the criminalist to identify the origin of the fiber or at least be able to narrow the possibilities to a limited number of sources
if the examiner is presented with fabrics that can be exactly fitted together at their torn edges, then ?
it is a virtual certainty that the fabrics were of common origin
the investigator’s task of looking for a minute strands of fibers often becomes one of identifying and presenting potential ?
carriers of fiber evidence
what should be packaged carefully in separate paper bags?
relevant articles
what should you do if it necessary to remove a fiber from an object?
the investigator must use clean forceps, place it in a small sheet of paper, fold and label the paper, and place the paper packet inside another container
major portion of microsamples submitted to laboratories
paint samples
paint samples usually involve paint transfer and vehicular accidents paint transfer to victim/victim vehicle. what should you determine?
determine chemical make-up of paint
determine make, model, and color (layers) of vehicle
paint ? from architectural sources - crimes against property are submitted occasionally
transfer
what type of paint transfer from a burglary?
paint smears transfer to tool used during commission burglary
paint spread onto a surface will dry into a hard film that can best be described as consisting of ?
pigments and additives suspended in the binder
automobile manufacturers normally apply a variety of ?
coatings to the body of an automobile
these coatings may include
electrocoat primer, primer surfacer, basecoat, and clearcoat
the wide diversity of automotive paint contributes to the forensic ? of an automobile paint comparison
significance
questioned and known specimens are best compared side by side under a ? microscope for ?
stereoscopic
color, surface texture, color layer sequence
what are crime labs often asked to idenitfy?
the make and model of a car from a small amount of paint and will make use of color charts for automobile finishes
when paint is to be analyzed, it is best to submit ? object to laboratory
entire
when this is impractical, paint must be ? from object and submitted
removed
collect sample from area close to the ?
alleged contact and any other additional samples
