1. Impression Analysis Tire Impressions, Footwear Impressions, Fabric Impressions, and Toolmarks

2. Shoe and Tire Impressions If shoe or tire is contaminated with blood, oil, or dust, it will leave a visible or latent print. –Visible prints are photographed –Latent prints are developed in a manner similar to latent fingerprints. –Electrostatic technique – Plastic film is placed over print and charged from a power supply, so that dust or powder is attracted to plastic. Impressions can also be plastic (3-D) in mud, snow, etc.

3. Locating and Casting Impressions Search for print in a manner similar to searching for fabric or glove prints. Plastic Prints are first photographed from directly above, and then a cast is made. Comparison prints are made by inking the soles of the shoes and placing them on an acetate sheet or tracing paper.

5. First spray the impression with shellac or clear lacquer. Allow it to dry. Add retaining frame (2” depth) Prepare casting material, and pour it in. Before it dries, scratch in identifying material: –Arrow indicating north –Case Number –Name of person preparing cast –Date

6. Class characteristics –Manufacturer –Model –Size Individual Characteristics –Imperfections –Nicks, scratches, missing material. –Wear pattern –Foreign materials (rocks,etc.) NOTE: Impression may not be exactly the same size due to stretching of materials, etc. FBI Maintains database of tires and shoes for comparison

7. Fabric Prints Gloves –Visible or latent prints can be left due to contamination Should be developed, photographed, and collected as if they were fingerprints –Plastic prints can be left in soft substances Cloth gloves – have snags, tears, or holes, as well as imperfections in weave pattern

8. Leather Gloves – wrinkle or crease formations, surface cracks, tears, or imperfections Glove prints are less strong than fingerprints and may be destroyed by too much powder. Lifting may destroy the print. Comparison prints are made on glass Fabrics (clothing) can leave impressions (hit-and-run accident, for example) and should be treated the same way.

9. Tool marks Similar to firearms analysis Implements used for cutting metal or prying apart objects develop nicks on their edges with use. These nicks produce striations on items that are cut with the tool. Comparison marks are made on soft metals, such as lead

10. Comparison microscope is used to compare tool mark impressions. –“comparative micrography” Cutting Tools (bolt or wire cutters) –Have a long blade –To avoid making numerous test cuts, chemical spot tests are performed to see what part of the blade cut a particular metal. Hammer – leaves an impression (rather than striations) – like a pin impression