1. AUTOMOBILE GLASS
With Thanks To Jerry Chisum Author: “Evidence and Crime Scene Reconstruction”

2. SHOOTING CAR WINDOWS
American automobiles have two types of window glass. The windshield is laminated.

3. SHOOTING CAR WINDOWS
American automobiles have two types of window glass. The windshield is laminated, the rest is stressed safety glass. Each acts differently upon breaking.

4. DID THE IMPACT COME FROM INSIDE OR OUTSIDE?
Side View
When regular glass is impacted the resulting fracture spreads out as it moves away from the site of impact.
Note how the angles spread outward forming a cone

5. DID THE IMPACT COME FROM INSIDE OR OUTSIDE?
With laminated glass the fracture spreads out normally, but only on the front side.
Laminate spreads out the energy.

6. POINT OF IMPACT Stressed Glass
All breaks radiate from one point.
Primary lines lead to impact point.

7. SEQUENCE OF SHOTS Stressed Glass
*First shot causes lines to radiate out and fracture the glass into many small pieces.

8. SEQUENCE OF SHOTS Stressed Glass
*First shot causes lines to radiate out and fracture the glass into many small pieces.
*Subsequent shots only break the small pieces. Only first shot can be traced.

9. SEQUENCE OF SHOTS Laminated Glass
O The first shot sends out radial lines
2nd shot lines may over extend 1st
The shock wave, carried by the
plastic causes 1st lines to grow.

10. SEQUENCE OF SHOTS Laminated Glass
O The first shot sends out radial lines
2nd shot lines may over extend 1st
The shock wave, carried by the
plastic causes 1st lines to grow.
Like this...

11. SEQUENCE OF SHOTS Laminated Glass
First Shot

12. SEQUENCE OF SHOTS LAMINATED GLASS
SECOND SHOT

13. SEQUENCE OF SHOTS LAMINATED GLASS
THE SHOCK WAVE
EFFECT
But which shot occurred first?

14. SEQUENCE OF SHOTS LAMINATED GLASS?
THE SHOCK WAVE
EFFECT
Beats me!
But which shot occurred first?

15. SEQUENCE OF SHOTS LAMINATED GLASS?
THE SHOCK WAVE
EFFECT
Beats me!
With LAMINATED GLASS You Just Can’t Tell!

16. ONE SIDED BREAK LAMINATED ONLY
A “star shaped” break on only one of the glass panes may be made by striking the opposite side.
Tap a dowel with a hammer, the opposite side breaks.

17. GLASS - VIDEO CLIPS Press Alt–Enter to view video in Full Screen Mode
Density Testing
Density Testing + CA
Hackle Marks
Press Alt–Enter to view video in Full Screen Mode
Press Alt–Tab to return to this slide.

18. GLASS - Hackle Marks
Let’s see if you really understand the “hackle Marks” video… you think the suspect in a case broke his own window from the OUTside of the house in order to fake a burglary. note: this is NOT the same as in the video
write an “if” / “then” hypothesis showing How you can prove it using glass hackle marks.

19. GLASS - Hackle Marks
hypothesis: If the impact occurred to the glass surface on the outside of the house,
then …

20. GLASS - Hackle Marks
hypothesis: If the impact occurred to the glass surface on the outside of the house,
then the hackle marks would be at right angles to the glass surface on the inside of the house. IN
OUT

21. GLASS - Hackle Marks
hypothesis: If the impact occurred to the glass surface on the outside of the house,
Rib Marks
then the hackle marks would be at right angles to the glass surface on the inside of the house. IN
OUT

22. GLASS - Hackle Marks
Inside
Outside
hypothesis: If the impact occurred to the glass surface on the outside of the house,
Rib Marks
then the hackle marks would be at right angles to the glass surface on the inside of the house. IN
OUT

23. GLASS - Hackle Marks
Inside
Outside
hypothesis: If the impact occurred to the glass surface on the outside of the house,
Rib Marks
Hackle Marks
then the hackle marks would be at right angles to the glass surface on the inside of the house. IN
OUT

24. GLASS - Hackle Marks
Inside
Outside
hypothesis: If the impact occurred to the glass surface on the outside of the house,
Rib Marks
Hackle Marks
90º
then the hackle marks would be at right angles to the glass surface on the inside of the house. IN
OUT