JS 113 Forensic Science

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Laboratory II Footwear impression laboratory

• JS 113 Forensic Science
• Slides by Jeremiah Garrido
• SCCCL

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Forensic Significance of Footwear Impressions

• Whether on hard or soft surfaces, the direct
  physical contact between the shoe and the
  substrate (surface) results in a transfer of
  class and individual characteristics from the
  shoe to the impression it leaves
• Two-Dimensional Impression
• Three-Dimensional impression

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Two-Dimensional Impressions

• As people walk about different they can acquire
  dust, dirt, residues, grease, oil, blood, and
  moisture onto shoes
• The shoes then deposit these materials back onto
  other surfaces they subsequently track over

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Three-Dimensional Impressions

• Walking over surfaces such as sand, soil, or
  snow, they may cause permanent deformation of
  that surface

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Class and Individual Characteristics
Class and individual characteristics are examined
to determine if a specific item of footwear made
the questioned crime scene impression, or if that
item can be eliminated.
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Detection and Recovery of Footwear Impressions

• The primary consideration for collection of
  impressions is for preservation and its
  reproduction for later examination by the crime
  lab
• Before any impression is moved or handled it must
  be _______________ with a scale
• Several shots should be taken over the impression
  with use of a Tripod and at different angles
  around impression with appropriate side lighting

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Detection and Recovery of 2-Dimensional Footwear
Impressions

• Electrostatic Lifting-utilizes high-voltage power
  source to create a static electrical charge that
  allows the transfer of a dust impression from the
  surface to a special black lifting film (mylar)
• Adhesive or Gelatin Lifting- the impression may
  be enhanced with fingerprint powder and lifted
  with a gelatin or adhesive lift.
• You will be performing adhesive test lifts on the
  three boots that may have been involved in the
  crime and comparing them, as footwear examiners,
  to a three-dimensional impression from the crime
  scene.

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Detection and Recovery of 2-Dimensional Footwear
Impressions

• Prints in blood
• Chemical enhancement
• Can still obtain DNA results
• LCV-Leucocrystal
• Violet
• Amido Black

Faint Diluted Bloodstain
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Detection and Recovery of 3-Dimensional Footwear
Impressions

• All three-dimensional impressions should be cast
  with dental stone. Dental stone is like plaster
  but sets much harder and has a higher compressive
  strength.
• Snow?

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What About Impressions in Snow ?
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Application of Snow Print Wax
Casting with dental stone
Collect submit Cast to lab
Inscribe case info initials
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Investigative Info Information Footwear
Impressions may provide (see lab handout)

• Identification of Footwear- class and individual
  characteristics
• Elimination of Footwear-
• Participation in the Crime-
• Location of Impression
• Rebuttal or Confirmation of Suspects Alibis-
• Determination of Shoe Brand-
• Linking scenes of Crime-
• Shoe Size-
• Association with other evidence-
• Gait Characteristics-
• Tracking-

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Lab Exercise CRIME SCENE

• During a heavy rainstorm in a large city in the
  Northeast, a convenience store owner was robbed
  and murdered in a similar manner to several prior
  robbery-homicides. The assailant quickly entered
  the store, pointed the gun at the victims head
  and shot him. The assailant then jumped over the
  counter and emptied the cash register. As the
  assailant left the store, police pursued him on
  foot. The long chase, through the storm, led
  through buildings and parks and over flat-topped
  roofs. The police backtracked the prints to a
  city park where he had hidden momentarily. In
  this covered area they found the gun. Next to
  the gun were several shoeprints of the same
  design. All of the shoeprints were
  photographed.
• Three individuals that fit the description of the
  suspect were brought in for questioning. Police
  observed that ALL three individuals were wearing
  the same brand shoe, which appears to have
  possibly deposited the shoeprints at the scene.
  Therefore, the shoes from these individuals were
  submitted to the crime lab for examination.

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Objective 1 Make a Known Test Impression of
Footwear Submitted

• Using paper fingerprint powder
• Produce a highly detailed sample of the class and
  individual characteristics of the shoes.
• Test impression will be compared to CS 3-D
  impression (cast)

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Objective 2 Make a Cast of One of the
Impressions at the crime scene to compare to the
Known Test Impressions taken in Objective One
After completing your objectives, using
individual characteristics, identify which shoe
submitted to the laboratory deposited the
impression at the crime scene