Physical “Trace” Evidence
Paint <ul><li>most frequently encountered in hit-and-run and burglary cases </li></ul><ul><li>often paint is transferred f...
Paint <ul><li>composition </li></ul><ul><ul><li>pigments – impart color and opacity </li></ul></ul><ul><ul><li>binder – pr...
Paint <ul><li>automotive finishing system for steel </li></ul><ul><ul><li>electrocoat primer </li></ul></ul><ul><ul><ul><l...
Paint <ul><li>automotive finishing system for steel </li></ul><ul><ul><li>basecoat </li></ul></ul><ul><ul><ul><li>colorcoa...
Paint <ul><li>microscopic examination </li></ul><ul><ul><li>color </li></ul></ul><ul><ul><li>surface texture </li></ul></u...
Entomology <ul><li>knowledge of insects </li></ul><ul><ul><li>used to estimate time of death </li></ul></ul><ul><ul><ul><l...
Entomology
Entomology <ul><li>determination affected by environmental factors </li></ul><ul><ul><li>geographic location </li></ul></u...
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Trace Evidence

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Trace Evidence

  1. 1. Physical “Trace” Evidence
  2. 2. Paint <ul><li>most frequently encountered in hit-and-run and burglary cases </li></ul><ul><li>often paint is transferred from one surface to another </li></ul>
  3. 3. Paint <ul><li>composition </li></ul><ul><ul><li>pigments – impart color and opacity </li></ul></ul><ul><ul><li>binder – provides support medium for pigments and additives </li></ul></ul><ul><ul><li>solvent – disperses pigments, binder etc. </li></ul></ul><ul><li>when applied, solvent evaporates leaving the hard binder with pigments suspended in it </li></ul>
  4. 4. Paint <ul><li>automotive finishing system for steel </li></ul><ul><ul><li>electrocoat primer </li></ul></ul><ul><ul><ul><li>epoxy based resins electrocoated to provide corrosion resistance </li></ul></ul></ul><ul><ul><ul><li>uniform in appearance and thickness </li></ul></ul></ul><ul><ul><ul><li>usu. black or gray </li></ul></ul></ul><ul><ul><li>primer surfacer </li></ul></ul><ul><ul><ul><li>completely smoothes out and hides any seams or inperfections </li></ul></ul></ul><ul><ul><ul><li>highly pigmented to “match” or hide contrast between primer and topcoat </li></ul></ul></ul>
  5. 5. Paint <ul><li>automotive finishing system for steel </li></ul><ul><ul><li>basecoat </li></ul></ul><ul><ul><ul><li>colorcoat </li></ul></ul></ul><ul><ul><ul><li>integrity of this layer depends on its ability to resist weather, UV radiation, and acid rain </li></ul></ul></ul><ul><ul><li>clearcoat </li></ul></ul><ul><ul><ul><li>unpigmented – applied to improve gloss, durability and appearance </li></ul></ul></ul>
  6. 6. Paint <ul><li>microscopic examination </li></ul><ul><ul><li>color </li></ul></ul><ul><ul><li>surface texture </li></ul></ul><ul><ul><li>color layer sequence </li></ul></ul><ul><ul><ul><li>when paint specimens possess colored layers that match in number and sequence of colors, the examiner can begin to relate the paints to a common origin </li></ul></ul></ul><ul><ul><ul><li>no accepted criterion for # of layers to conclude a common source </li></ul></ul></ul>
  7. 7. Entomology <ul><li>knowledge of insects </li></ul><ul><ul><li>used to estimate time of death </li></ul></ul><ul><ul><ul><li>after death, blowflies are the first to infest the body </li></ul></ul></ul><ul><ul><ul><li>eggs laid in remains, hatch into maggots or fly larvae </li></ul></ul></ul><ul><ul><ul><li>consume human organs and tissues </li></ul></ul></ul><ul><ul><ul><li>ID specific insects and stage of development to estimate time of death </li></ul></ul></ul>
  8. 8. Entomology
  9. 9. Entomology <ul><li>determination affected by environmental factors </li></ul><ul><ul><li>geographic location </li></ul></ul><ul><ul><li>climate </li></ul></ul><ul><ul><li>weather conditions </li></ul></ul><ul><li>determination affected by condition of body </li></ul><ul><ul><li>wrapped vs. unwrapped </li></ul></ul><ul><ul><li>material used </li></ul></ul>

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