1. Casts & Impressions
Chapter 15

2. Types of Impressions Patent impressions: visible impressions
Soil, dust, paint, blood
Latent impressions: invisible
Special dusting, electrostatic techniques, chemical developers
Plastic impressions: three-dimensional
Snow, mud, Soil, soap
Easily lost – photography is important!

3. Individual or Class?
Tread pattern – identify brand & size, but not a specific individual
Ex: tires or shoes
Distinguishing characteristics may be individual evidence
Unusual wear, split on a shoe sole
Dental impressions are typically individual evidence

4. Shoe Impressions
Can determine shoe size, job or personality (type), weight (depth of impression), brand can provide information about the buyer (finances, activities, etc.)
Cannot determine height from shoe size!
Databases exist that contain names of specific manufacturers and tread patterns used to identify different types of shoes
Many manufacturers use the same generic sole pattern
Used as class evidence to link a suspect to the crime scene by matching footwear to an impression

5. Shoe Wear Patterns
Wear pattern can differentiate two of the same pair of shoes
Everyone has a characteristic way of walking/usage
If individual character is strong enough, can be individual evidence
Unique holes, cuts or debris; direction of prints/impressions (point out or in); walks on toes or heels, etc.

6. Gait & Tracks
Numerous prints together tell an investigator about the person’s gait, or walking habits
Injury or limp: assymetrical gait
Carrying a heavy weight
Walking vs. running
Help recreate events
Number of people at the crime scene
Movements of individuals at the crime scene (one room or several rooms?)
Entrance and exit to the crime scene

7. Collection of Shoe Impression Evidence
photographing impressions
2. lifting latent impressions
3. casting plastic impressions

8. Photographing Impressions
Must be done first
Perpendicular lens to reduce distortion
Multiple photos from at least two angles
Identifying label and a ruler (both with and without)
Use oblique lighting
Can use a light coat of color contrast paint if it is faint

9. Lifting Latent Impressions
Shoe can leave a thin film of substances from the plastic in sole or dirt
Luminol can make bloody footprints visible and able to be photographed
Dusting of latent print (like fingerprints) to reveal an impression and make it visible to be photographed and lifted
Electrostatic lifting and gel lifting techniques to capture invisible impression

10. Casting Plastic Impressions
Three-dimensional impression is called a cast and may be made to preserve physical evidence
Dirt: Plaster of Paris (spray with hairspray first)
Snow: spray wax, then dental stone

11. The Man in the Bruno Magli Shoes
June 13, 1994 – murder of Nicole Brown Simpson & Ronald Goldman
Bloody footprints, determined to be made by size 12 Bruno Magli shoes, tracked the victims’ blood along the path
Specialists determined that the impression was made about 20 minutes after the attack.
OJ Simpson denied owning a pair of Bruno Maglis, and the prosecutor could find no way to dispute this fact
Footprint evidence was of little value in the criminal case
After criminal trial ended, photo was found showing Simpson wearing similar shoes
In civil case that followed jurors believed the attacker made the footprints, and Simpson was found responsible for the deaths of Brown and Goldman