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Tool Marks and Impressions

Tool Marks and Impressions. 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:.

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Tool Marks and Impressions

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  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.

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  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. http://www.irlab.com/quinsee/images/ShoePrint.gif

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  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

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