Glass Evidence Part I

Trace Evidence – Part II

Physical Properties Physical Properties – describe a substance ______reference to any other substances Examples: - ______- ______- ______Chemical Properties Chemical Properties – describes the behavior of a substance when it reacts or combines with ______Examples: - Wood burning to form ______- ______test with Marquis reagent turns purple Comparing Glass Fragments Glass can be ______into fragments and minute particles - Pieces can get lodged in shoes or garments - Can place ______at scene of the crime - Can connect a suspected car to ______- Can be used to prove the body was ______Types of Glass “Soda-lime” glass – easy to manipulate, made of sand mixed with soda and lime - Used mostly in ______and bottle glass - Mixed with other materials to create ______and heat-resistant glass (like ______) Tempered glass – strength is added by rapidly heating and cooling the glass during manufacturing - Does not ______- Fragments, or “______,” when broken - Used mostly in side and rear car ______- Also used in windshields of some ______cars Laminated glass – two sheets of ordinary glass bonded together with a ______film - Used in the windshields in most ______cars Glass Comparison Must have the glass from the crime scene and a sample from a suspected car or item Difficult to individualize (crime scene and suspect glass come from ______) - Possible if fractured glass ______perfectly - Possible if ______elements in the glass match between crime scene and suspect glass Glass Fractures Glass ______in response to any force that is exerted on any of its surfaces - Once it can no longer bend, it ______When glass is broken by a projectile, two types of fractures are created: ______Fracture – a crack in the glass that extends outward like the spoke of a wheel from the point at which the glass was struck ______Fracture – a crack in a glass that forms a rough circle around the point of impact Can you determine the projectile from the size and shape of the hole? ______! Bullet and ______sent at a very high speed will leave very similar fractures A large stone and a close range bullet have very similar fracture patterns BUT – shooting the close range bullet would have left ______residues A high speed projectile (like a ______) leaves a round, crater-shaped hole surrounded by a symmetrical pattern of ______cracks Which side is a wider hole – entrance or exit? - ______

Blunt Force Fractures - Patterns similar to those by a projectile - However, not as ______- Due to impacting force being dispersed over a ______area Multiple Glass Fractures - A fracture always ends at an ______line of fracture Heat Fractures - Heat crack is usually ______- Has a ______edge - No indication of ______