Last Modified: 2016-03-08
When an object/material is pressed against another object/material and some force is applied, an impression is left.
- shoe soles and heels, tire treads, fingerprints, footprints, lip prints, tools, metal dies, ribbing and texture in fabric
- Random imperfections make individualization possible
- Fingerprints, shoe soles, tool marks, tire treads and serial numbers
- 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
Three-dimensional pattern or marking must contain some characteristics that are unique to that object
- Come about as an object is used
- Characteristics are random in nature
- 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
- Complete visual record
- Determine how best to preserve/enhance impression
- 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
- 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
- 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
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