Glass Fractures bsapp.com

Glass How broken? Link a suspect to a crime scene Fingerprints Blood bsapp.com

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

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

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

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

Fractures Concentric Radial bsapp.com

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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Direction of Penetration A projectile hole is inevitably wider at the exit side bsapp.com

Direction of Penetration Radial Concentric bsapp.com

Stress Marks The perpendicular edge of stress marks always face the surface on which the crack originated bsapp.com

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

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

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