1. Tool Mark & Impression Evidence

2. Types of Impressions
Patent Impressions – two dimensional, visible impressions
Latent Impressions – impressions that are hidden to the naked eye
Plastic Impressions – three-dimensional impressions

3. Shoe Impressions
Can provide information such as height of the individual, how someone moves, and identify other crime scenes
Databases contain the names of specific manufacturers and tread patterns that can be used to identify different types of shoes.

4. Shoe Wear Patterns
Some factors that personalize a person’s footwear include:
- Body weight
- The way a person walks (gait)
- The surface on which the person
usually walks.
- Debris that became embedded in the
tread or unique holes and cuts in the
tread.

5. Lifting Impression Evidence
Latent Impressions:
Luminol for bloody prints
Electrostatic lifting

6. Patent Impressions:
Very complete photographic evidence collection is necessary for most patent impressions as they often cannot be saved.

7. Plastic impressions can be lifted using plaster or dental stone.

8. Tire Impressions
Can be lifted from dirt, snow, sand and even standing water.
Lifted using various substances including plaster of paris, dental stone, sulfur, snow-print wax
Can leave patent, latent, or plastic tread patterns.

9. Tread Impressions
Ridges and grooves of discovered impressions are counted across the entire width.
Unique characteristics such as wear or pebbles embedded in the grooves are noted
A print of a suspect’s tire impression through one full revolution is taken

10. Identifying Characteristics
Front and Rear Track Width – measured from the center of each tire to the center of the opposite tire.

11. Wheelbase – the distance between the enter of the front axle to the center of the rear axle.

12. Turning diameter – the distance required for a car to make a U-turn (1/2 of circle).

13. Accident Reconstruction
There are three basic types of tire marks:
Skid Marks – forms when someone brakes suddenly and locks the wheels.

14. Yaw Marks- produced when a vehicle travels in a curved path faster than the vehicle can handle and skids sideways.

15. Tire Scrub - produced by a damaged or overloaded tire or tires during or immediately after impact.

16. Dental Impressions
Like fingerprints, dental impressions are usually considered individual evidence.

17. Factors that affect our dental impressions include:
Number of teeth/Missing teeth
Coloration of teeth
Size of teeth
Alignment of teeth and distance
between teeth
Unique fillings, crowns, caps
Overall condition of teeth
(breakage/chipped teeth, grinded
teeth etc…)

19. Structure of Teeth

20. Bite Mark Comparisons Up to 76 points of comparison
Places where locations on bite where impressions are often detailed
Comparison includes:
Dental chipping, surface indentations, distances between teeth, alignment of teeth, angle of mouth arch, absence of teeth
Bite mark should be photographed with ruler included as soon as possible
Bite mark should be swabbed, may contain DNA from saliva

22. Tool Marks
Tool Marks are any impression, abrasion, or cut made when contact occurs between a tool and an object.
Even mass-produced tools have minor differences.

23. Indentation Marks
Indentation marks – made when a tool is pressed against a softer surface.

24. Abrasion Marks
Abrasion Marks – made when surfaces slide across one another.

25. Cut Marks
Cut marks are produced along the edge as a surface is cut.

26. Tool Mark Analysis
Usually done with a comparison microscope.