1. Tool Marks and Impressions

2. Tool Marks and Impressions
A tool mark is any impression, cut, gouge, or abrasion caused by a
tool coming in contact with another object.
A “tool mark” can be caused by an endless list of objects:
Examples:
A screwdriver is most often used to tighten or loosen screws.
However, if it is used to pry open a widow it will leave impressions
In the window sill.
Car tires leave impressions in the ground.
Even a button on your shirt will leave an impression on your skin
if pressed hard enough.

3. Tool Marks and Impressions
Tool marks come in two general categories:
Compression Marks
Scraping Marks

4. Tool Marks and Impressions
In general tool marks reveal class characteristics, such as size
and shape of tool used.
However, once a tool has been used minute random markings on the
surface can impart individual characteristics to objects.

5. Tool Marks and Impressions

6. Tool Marks and Impressions

7. Tool Marks and Impressions
Footprints
Footprint impressions are useful information when collected at a
crime scene.
Initially shoe prints are classified as class evidence. However,
over time all shoes acquire their own wear pattern, nicks, markings,
etc.
Once a shoe has been worn for a period of time, it becomes unique,
and it then becomes individualized.

8. Tool Marks and Impressions

9. Tool Marks and Impressions
Bloody Shoe Print

10. Tool Marks and Impressions
Footprints made in the ground can be cast with plaster and used
for comparison.

11. Tool Marks and Impressions
Tires
Tire tread impressions and prints can be useful evidence left at a
crime scene.
As in any mass produced item, initially a new tire will exhibit class
characteristics.
However, in time the tire will acquire a unique wear pattern making
each tire individual.

12. Tool Marks and Impressions
Tires
Dimensions left by tire marks or impressions are helpful in identifying
a particular vehicle.
Tread Width – the distance across tread pattern.
Typically larger trucks and SUV’s have larger tires than compact cars.

13. Tool Marks and Impressions
Tires
Tire marks can also indicate a vehicles direction of travel.
When a vehicle is traveling in a straight line, the rear tires travel
over the prints made by the front tires.
Therefore, a turn is the best place to see clear prints.

14. Tool Marks and Impressions
Describe how this car was traveling.
Rear Tires Forward Again
Rear Tires Reverse
Front Tires
Forward
Front Tires
Reverse
Rear Tires
Forward
Front Tires
Forward Again

15. Tool Marks and Impressions
Bite marks
Bite marks left on skin can leave impressions which can be traced
back to suspect.
Digitally Enhanced

16. Tool Marks and Impressions