impression evidence
- Created by: meganjayne15
- Created on: 03-05-14 18:06
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- Impression Evidence
- what is it?
- when objects or materials retain the characteristics of other objects or materials through direct contact they leave a unique impression
- footwear - tyre tracks - tool/instruments
- when objects or materials retain the characteristics of other objects or materials through direct contact they leave a unique impression
- tyre marks
- impressions left by tyres on the surface onto which a vehicle drove
- sometimes surfaces are not suitable to retain the impression
- but if the surface is sort i.e. mud/dirt/snow, the tyres will often leave an impression (3D mark)
- sometimes surfaces are not suitable to retain the impression
- can be matched back to a particular vehicle due to the thread of the tyres and the wear
- recovery technique
- cast using dental stone - same as footwear
- dental stone gives finer detail
- photograph and enhance through the use of light and chemicals
- cast using dental stone - same as footwear
- similar to footwear examination - just a larger scale
- photograph
- cast
- test prints on inked sheets
- cast
- photograph
- similar conclusions as footwear
- limitations
- complex structure
- variation in patterns
- examination and comparison
- pattern
- pattern size
- wear
- damage
- elimination prints
- ambulances, police vehicles, fire service and other legitimate access
- not as easy as footwear to recover and eliminate - limitation
- ambulances, police vehicles, fire service and other legitimate access
- impressions left by tyres on the surface onto which a vehicle drove
- tool marks
- found at various crime scenes
- burglary
- criminal damage
- fires
- wide range of tools available
- screwdrivers
- jemmys
- bolt croppers
- impressed detail
- pressing detail
- crushing detail
- physical impression of tool
- can show class and individual characteristics
- striation detail
- dynamic scrapping action
- cutting action
- recovery technique
- photograph
- cast with silicone material with hardener i.e. mikrosil and hardener
- cut out mark if able too
- comparison
- use comparator
- tool vs cast
- examine for matching detail using split screen stero microscope
- cast from scene and cast from tool
- make notes and photograph
- examination
- shape, size, apparent detail and measurements
- found at various crime scenes
- what is it?
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