Other Impressions

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Other Impressions

• What other impressions can you think of at a
  crime scene?
• Shoe
• Tire
• Fabric
• ???
• How are impressions preserved?

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Lifting Impressions

• Two methods 1) similar to lifting prints, 2)
  electrostatic lifting
• If made in light deposits of dust or dirt, place
  lifting material over impression, use fingerprint
  roller to eliminate air pockets, and lift
  impression.

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2. Electrostatic Lifting (dust impressions)

• Electrostatic charge on comb and tissue paper
  example
• Mylar film placed over dust mark and pressed
  against impression with roller
• Electrostatic unit gives a charge to the film,
  attracting the dust

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2. Electrostatic Lifting (dust impressions)
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Casting Impressions

• Class I dental stone (gypsum) is used to make
  casts of shoe and tire impressions.
• Cast needs to dry 24-48 hours before transporting
  to the lab.
• For snow impressions, spray with Snow Impression
  Wax, then pour Class I dental stone to make cast.

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Casting Impressions, cont

• http//www.sccja.org/csr-cast.htm

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Casting Impressions, cont

• For shoe impressions in blood, the impression is
  developed and enhanced using various chemicals.

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Case Study

• O.J. Simpson

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Bite Marks

• How would bite marks differ from person to
  person?
• What are the odds of two people having the same
  bite marks?
• How are bite marks detected?
• Visible
• UV light

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Bite Marks, cont.

• How is evidence collected?
• 1st step
• 2nd step
• Its like playing the game Operation.
• Ted Bundy