1. GLASS EVIDENCE Common evidence Found everywhere Burglaries
Hit and run accidents

2. Types of glass Soda lime glass Bottles Windows
Most common type of glass

3. Borosilicates Heat resistant glass
Commonly found in headlight lenses and cookware

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

5. Tempered Glass break

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

7. Proposed legislation
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
This was proposed after the Oklahoma City bombing – many deaths & injuries resulted from flying glass.

8. Glass at crime scenes Pieces Particles
Large enough to be physically matched to other pieces
Put back together like a jigsaw puzzle
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

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

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

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

12. Radial crack – right angle on reverse side of force

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

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

15. Radial crack - From what direction did the force come?

16. A fracture will stop at a previously existing fracture

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

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

19. Glass in suspect’s shoe