Forensics - glass
- Created by: Ashlee
- Created on: 28-04-15 15:39
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- Glass
- properties
- transparent/translucent materials composed of fused inorganic materials
- variety of chemical compositions
- variables in elements alters characteristics and use
- toughened glass
- high boron content
- resistant to thermal shock
- super heated and rapidly cooled
- increased bending strength
- perfect for car windows
- soda lime glass
- most common
- windows; drinks; containers
- silica; soda & lime
- probative value
- evidential potential
- physical/optical/elemental characteristics
- analysis
- macroscopic
- radial and concentric cracks
- 3r rule - radial fracture; rear surface; right angles
- primary and secondary fractures
- backward fragmentation
- thickness
- colour
- uniformity
- curvature
- surface conditions
- UV light
- glass fluoresces when use UV light
- due to float glass manufacture process
- tin diffuses into glass
- macroscopic
- collection
- take from window not floor
- toughened = 50 pebbled
- sode lime = 6 pieces marked inside and outside
- refractive index
- RI = n
- ratio between speed of light in vacuum and speed of light through medium
- n = C/v
- C = speed of light
- v = velocity thought medium
- air = 1.0008
- water = 1.330
- ice = 1.310
- glass = 1.510
- diamond = 2.417
- ruby = 1.760
- measured by the emersion method - see if RI is same as oil that surrounds it
- how it breaks
- 1) struck
- 2) bends
- 3) begins to fracture with radial fracures
- 4) stress continues - concentric fractures
- 5) continues with radial and concentric fractures until process stops
- 4) stress continues - concentric fractures
- 3) begins to fracture with radial fracures
- 2) bends
- 1) struck
- probative value
- direction of force
- type of weapon
- distribution of glass
- sequence of events
- associated evidence - link to victim/suspect/place
- properties
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