1. Glass Fractures
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2. Glass How broken? Link a suspect to a crime scene Fingerprints Blood
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3. Glass Evidence Collect evidence from crime scene Analysis:
Physical Properties (color, thickness, type)
Optical Properties (refractive index: the speed of light in a vacuum divided by the speed of light in the medium or density)
Elemental Analysis
Report findings

4. Composition of Glass
Hard brittle substance made of mostly silicon dioxide (Sand)

5. Types of glass
Tempered glass: is made strong by rapid heating and cooling process that introduces stress to the glass
When the tempered glass breaks it breaks into tiny cubes with no sharp edges
Tempered glass is used in the side and back windows of the car

6. Types of glass
2) Laminated glass: safety glass very strong because it is made of 2
layers of glass sandwiching a layer of plastic
Auto window shields are this type
Other types are- Wire glass, Colored glass, Light sensitive glass

7. Fractures
Concentric
Radial
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8. Fractures
Radial fracture: crack in glass that extends from the point at which the glass was hit
Concentric fracture: crack in glass that forms a rough circle

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11. Direction of Penetration
A projectile hole is inevitably wider at the exit side
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12. Direction of Penetration
Radial
Concentric
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13. Stress Marks
The perpendicular edge of stress marks always face the surface on which the crack originated
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14. Direction of Force
Glass breaks due to tension rather than compression (stretch or pull force vs. squishing or collapsing force)
Surface that breaks 1st is the opposite side of the impact zone
3R Rule: Radial cracks for a Right angle on the Reverse side of the force

15. Successive Penetrations
A fracture always terminates at an existing line of fracture
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