Trace Evidence: Glass

  1. Glass Introduction
  2. = a ______type of trace evidence
  3. ______of glass
  4. Common material in our ______
  5. Found in many ______, sizes, ______, and types
  6. Composed of fused ______material
  7. Mixture of:
  8. ______
  9. ______
  10. ______
  11. Other trace elements
  12. Variation in ______formulas can alter significantly its characteristic _____
  13. Additives’ responsibilities
  14. Alumina (______)
  15. Aluminum oxide
  16. Improves chemical ______and ______
  17. Boron Oxide (______)
  18. Addition used in borosilicate & aluminoborosilicate glasses.
  19. Very ______
  20. Lime (______)
  21. Added to improve ______& chemical ______
  1. Lead oxide (______)
  2. High lead content lowers ______=______hardness, but ______refractive index
  1. ______of Glass
  2. Aluminosilicate & borosilicate
  3. Can ______temps.
  4. Laminated glass
  5. Glass w______- used in car ______
  6. ______glass
  7. Fine crystal
  8. Soda lime glass
  9. ______& ______glass, glass containers, electric ______, art objects
  10. ______(stressed) glass
  11. Side & back windows of cars; breaks into ______
  1. Glass as Evidence
  1. Physical—______
  2. Can be used to ______people at a crime scene and ______sequence of events

○Does this make glass CLASS or INDIVIDUAL evidence???

Can be used to reconstruct events

______

Blood

Glass is slightly ______

When it reaches its ______= ______

this leads to ______

2 Distinct types of fractures

1. ______

2. ______

Key = ______cracks will ______when they hit ______cracks. This info can help determine ______of events.

○Direction of Impact

  • Found from ______marks on the ______of broken glass.
  • At the ______of ______,

glass will break with a ______

pattern (shell-like)

  1. Density determination =
  2. Refractive index (____) determination
  3. Background:
  1. Refraction = the ______of a ______wave as it passes from one ______to another
  2. Refractive Index (RI)= a ______of the speed of ______in a vacuum to the speed of light in ______substance

○Sample calculation: speed of light in vacuum is 3.00 x 1010 and the speed of light in water is 2.25 x 1010

○Thus RI of water =

  1. Determining the RI from samples in an investigation:
  1. Different types of ______will have ______
  1. To analyze this property

Glass fragments can be ______in a liquid with a ______refractive index to help ______the RI of the ______

  1. Analysis method 1

Liquid / Refractive index
Ethyl acetate / 1.373
n-butyl alcohol / 1.402
Olive oil / 1.467
Corn oil / 1.473
Castor oil / 1.482
Methyl salicylate / 1.522
Clove oil / 1.543
Canola oil / 1.465-1.467

--If the liquid has the ______RI as the glass sample, the glass will ______under a microscope.

--If the liquid has a ______or ______RI, the glass is visible and a ______appears around perimeter (we call this halo the ______).

. . . when RIs are the ______, the Becke line ______

. . . ifBecke line appears on the ______perimeter = Glass has _____

. . . ifBecke line appears on ______perimeter = Glass has ______

  1. Analysis method 2
  • RI is dependant on:
  • The ______of light
  • The ______of the medium
  • When the temp. of a liquid is changed, the RI changes rapidly, but the RI of an immersed solid will not

○______usually used

○Oil ______so RI can be determined from its temp.

○Sample glass is immersed in oil

○Oil is ______to determine match temp.

  • Glass ______
  • Oil RI = Glass RI
  1. Chemical Tests
  • ______
  • Test for silicates, metal oxides, trace evidence