Impression Evidence

• Fingerprints remain the same throughout life
  
• A single major disparity may eliminate a known fingerprint, may not be the case for other types of impression evidence

• Involves a donor and a recipient
  
• Donor contains some three-dimensional markings
• Recipient is made of a material that can form and hold a negative image of the donor markings

• Polish the surface of the metal
  
• Treat with acids
  
• Rinse off the acids
  
• Photograph the numbers as they are restored
  

Footwear prints will be left at the point of entry, at the crime scene and at the point of exit

- May be difficult to locate if latent or invisible

- May be mixed with prints of other people

1. Complete visual record
   
2. Determine how best to preserve/enhance impression
3. Cast Impression

• Type, manufacturer, model, exact size
  
• Match to actual footwear that made impression
• Number of people and suspects at the scene
  
• Uncover characteristics of the gait of the wearer
  

• Plaster of Paris
  
• Dental plasters and stone
• Snow
• Paint Thinner, Spray Paints, Paraffin, Sulfer, etc.

• Soft, even after drying
  
• Made up of large particles that may cause the loss of crucial detail
  
• Require the use of forms and reinforcing materials
  

• Dense, uniform, smaller particle size
  
• Quick drying and show more detail
  

• Available in a spray can
  
• Results in fragile, thin cast that shows great detail
  
• After drying, is filled with dental casting mixture
  

• Tape (or Gelatin Materials) = Imprints in dust/powder
  
• Electrostatic Lifting Device (most popular)

• Impressions in grease, oil, blood, cushions or carpeting materials may be impossible to lift

• A large, static electricity charge will strongly attract dust and other fine powders
• A low-current, high voltage charge is put across a film that attracts the particles from the impression
• Transferred image can then be photographed

• Footwear: No set number
  

• Designed not only for traction, but for channeling away water, reducing noise, and increasing comfort
  

1. Photography
2. Drawings
   
3. Casting for 3-D impressions (at the scene - treads cannot be moved)

• 2-D: impression is lifted with tape (dust/power)
  
• 3-D: a cast can be made
• Negative: Residue on the surface (e.g. floor) is transfered to the shoe.
• Positive: Residue on the shoe is left behind on the surface (floor)

• Theory of "The Criminal Man": natural-born killers
  
• Influenced entire history of criminology
• "Criminals are innately driven to act as an ape/savage would"
• Criminals could be identified by unattractive features