FRSC 200 FINAL EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS VERIFIED GRADED A++
Is glass evidence class evidence? Can it be individualized?
Glass is generally class evidence except when a fracture match is found (considered to
be an individual characteristic)
What are characteristics of glass?
Amorphous solid (no ordered structure), pure form made up of silicon and oxygen
molecules (SiO2), high melting point (over 2,0000C), hard/brittle like solid
What are the different types of glass? Can you give an example of each?
float glass/soda lime glass-windows, picture frames, flat glass objects (SiO2 with
sodium carbonate Na2CO3 and calcium oxide CaO)
Tempered glass - auto glass, safety glass, shower doors, plate glass, windows in store
(same chemical makeup as soda lime glass, but stronger. When broken this glass
fractures into small blunt pieces
Borosilicate glass - lab glassware, kitchen items-pyrex, (SiO2 with boron)
Tinted glass - has colorants that reduce glare/heat penetration, for decorative use (SiO2
with additives/colorants)
Leaded glass (crystal) - wine glasses, fine dining, figurines (SiO2 with lead oxide)
How is sequencing of fractures performed? What is looked at?
when an object hits glass, the resulting hole/indentation is called the point of impact,
when a glass object has multiple points of impact, the sequence in which they occurred
can be determined by examining the fracture lines that stem from each point of impact
, Radial fracture lines - form first, extending outward from the break point
Concentric fracture lines - form second, creating a circle about the breaking point
Radial lines always end in existing radial lines
How is the direction of force of a bullet through glass determined? (what are the
differences between entry vs exit holes?)
when small projectiles (bullets) travel through glass, can identify the direction in which
they traveled by distinguishing entry vs exit holes
Entry holes = smaller holes, smooth surface
Exit holes = wider hole, crater shape, rough surface
What are the class characteristics of glass that can be analyzed by most labs?
physical appearance - size, shape, thickness - color, density, refractive index
Class characteristics of glass are limited because glass is inert which makes it difficult
to dissolve in solvents and perform chemical analyses
Some labs may be able to perform elemental analysis on glass evidence using
inductively coupled plasma mass spectroscopy (ICP/MS) - digests glass sample and
determines chemical composition, ICP/MS in few crime labs
What is refractive index and is it useful for glass analysis?
the ratio of the velocity of light in a vacuum to its velocity in a medium (RI = velocity of
light in vacuum/velocity of light in medium), as light passes from one medium to
another, it slows down, causing it to bend or refract
The refractive index of small pieces of glass can be determined using commercially
available liquids whose RIs' are known
Crime labs also use a hot stage microscope for determination of RI, a glass fragment is
COMPLETE SOLUTIONS VERIFIED GRADED A++
Is glass evidence class evidence? Can it be individualized?
Glass is generally class evidence except when a fracture match is found (considered to
be an individual characteristic)
What are characteristics of glass?
Amorphous solid (no ordered structure), pure form made up of silicon and oxygen
molecules (SiO2), high melting point (over 2,0000C), hard/brittle like solid
What are the different types of glass? Can you give an example of each?
float glass/soda lime glass-windows, picture frames, flat glass objects (SiO2 with
sodium carbonate Na2CO3 and calcium oxide CaO)
Tempered glass - auto glass, safety glass, shower doors, plate glass, windows in store
(same chemical makeup as soda lime glass, but stronger. When broken this glass
fractures into small blunt pieces
Borosilicate glass - lab glassware, kitchen items-pyrex, (SiO2 with boron)
Tinted glass - has colorants that reduce glare/heat penetration, for decorative use (SiO2
with additives/colorants)
Leaded glass (crystal) - wine glasses, fine dining, figurines (SiO2 with lead oxide)
How is sequencing of fractures performed? What is looked at?
when an object hits glass, the resulting hole/indentation is called the point of impact,
when a glass object has multiple points of impact, the sequence in which they occurred
can be determined by examining the fracture lines that stem from each point of impact
, Radial fracture lines - form first, extending outward from the break point
Concentric fracture lines - form second, creating a circle about the breaking point
Radial lines always end in existing radial lines
How is the direction of force of a bullet through glass determined? (what are the
differences between entry vs exit holes?)
when small projectiles (bullets) travel through glass, can identify the direction in which
they traveled by distinguishing entry vs exit holes
Entry holes = smaller holes, smooth surface
Exit holes = wider hole, crater shape, rough surface
What are the class characteristics of glass that can be analyzed by most labs?
physical appearance - size, shape, thickness - color, density, refractive index
Class characteristics of glass are limited because glass is inert which makes it difficult
to dissolve in solvents and perform chemical analyses
Some labs may be able to perform elemental analysis on glass evidence using
inductively coupled plasma mass spectroscopy (ICP/MS) - digests glass sample and
determines chemical composition, ICP/MS in few crime labs
What is refractive index and is it useful for glass analysis?
the ratio of the velocity of light in a vacuum to its velocity in a medium (RI = velocity of
light in vacuum/velocity of light in medium), as light passes from one medium to
another, it slows down, causing it to bend or refract
The refractive index of small pieces of glass can be determined using commercially
available liquids whose RIs' are known
Crime labs also use a hot stage microscope for determination of RI, a glass fragment is
