GLASS EVIDENCE Common evidence n Found everywhere n

GLASS EVIDENCE Common evidence n Found everywhere n Burglaries n Hit and run accidents n

Types of glass n Soda lime glass – – – Bottles Windows Most common type of glass

Borosilicates n Heat resistant glass – Commonly found in headlight lenses and cookware

Tempered glass Most commonly found in side and rear windows of U. S. autos n Also found in entry doors and shower doors n Fragments into small pieces when broken n

Tempered Glass break

Laminated glass Two sheets of glass with a layer of plastic between n When broken the plastic layer keeps the glass together n Most commonly found in auto windshields n

Proposed legislation n Federal buildings and public safety buildings would be required to use laminated glass. This would reduce the # of injuries in the event of an explosion n This was proposed after the Oklahoma City bombing – many deaths & injuries resulted from flying glass.

Glass at crime scenes n Pieces – Large enough to be physically matched to other pieces – Put back together like a jigsaw puzzle n Particles – Too small to be fit together – analysis will require using the physical properties of the glass – Will provide class characteristic evidence only – Refractive index is the most common property

Fracture patterns Penetration by a projectile creates a cone shape n This can help in determining direction and possibly the angle of penetration n

Glass breaking When the glass breaks two types of cracks form on the glass n The glass actually breaks on the opposite side of the force first n

Radial & concentric cracks Radial crack – begins at the penetration point and travels away from that point n Concentric – form a rough circle around the penetration point n

Radial crack – right angle on reverse side of force

BE CAREFUL… n The opposite will happen in a concentric crack n Make SURE you are dealing with a radial crack n Reconstruction of the window is necessary

This determination is helpful to… n Determine inside and outside of recovered glass n Direction of force n Fingerprints and footwear – inside or outside of glass

Radial crack - From what direction did the force come?

A fracture will stop at a previously existing fracture

When glass breaks… Most of the glass goes in the direction of the force n A lesser amount will come toward the force – for up to 10’ n

Finding glass evidence n Check hair, clothing and shoes (bottom & top) of suspects n Check objects used to break windows or bullets n Collect all available glass as evidence – better luck finding matching edges n Use a druggist fold – not envelopes n Look under vehicles in hit & run cases

Glass in suspect’s shoe