Footwear Impression Evidence

1
Footwear Impression Evidence

• Definition Impressions or marks formed by full
  or partial contact with the outsole of a shoe.

2
Footwear Evidence

• Two-dimensional Footwear Impressions
• Length and width, but no appreciable depth.
• Positive or negative impression
• Wet or dry origin of impression

3
Footwear Evidence

• Three dimensional Impression
• Length, width, and depth
• Substrate types (i.e. snow or mud)

4
Collection of 2D Footwear Impressions

• Submit original impressions on moveable object.
• Photographing impressions with oblique light,
  black and white film and filters.
• Lifting impressions.
• Submit footwear with similar class
  characteristics.

5
Collection of 2D Footwear Impressions

• Types of Lifts
• Adhesive lifts
• Powdering adhesive lifts
• Static lifts
• Gelatin lifts
• Carbon paper lifts

6
Collection of 3D Footwear Impressions

• Photographing with oblique lighting, black
  white film, and filters.
• Casting impressions in different substrate.
• Submitting footwear with similar class
  characteristics.

7
Collection of 3D Footwear Impressions

• Different substrates
• Soil or mud
• White or buff colored dental stone (best detail).
• Plaster of Paris
• Snow
• Snow wax spray dental stone
• Paraffin
• Sulfur (best detail)

8
Footwear Evidence

• Class Characteristics Intentional or unavoidable
  characteristics that repeats during the
  manufacturing process and is shared by more than
  one shoe.
• Design or pattern
• Physical size and shape

9
Footwear Evidence

• Individual Characteristics Those characteristics
  which result when something is randomly added to
  or taken away from a shoe outsole, that either
  causes or contributes toward making that outsole
  unique.
• Wear pattern
• Random features (i.e. cuts, scratches, tears)

10
Footwear Impression ExaminationAn examiner may
utilize the following techniques for generating
known impressions for comparison.

• 2D impressions
• Photographs
• 2D test impressions
• transparencies

• 3D impressions
• Photographs
• 3D test impressions
• transparencies

11
Footwear Impression Examination

• Observation of class characteristics
• The significance of class characteristics is used
  for elimination or inclusion of a group of shoes.
• Observation of class and individual
  characteristics
• The significance of class and individual
  characteristics is used for the elimination or
  inclusion of a specific shoe.
• A positive identification is when the questioned
  impression and the shoe share a combination of
  confirmed class and random characteristics, that,
  in the opinion of the examiner, could not be
  repeated on another outsole.

12
Tire Impression Evidence

• The evidence collection procedures for tire
  impressions is handled like 2D and 3D footwear
  impressions.