The document discusses different types of glass and forensic analysis of glass evidence. It provides information on the physical, optical, and chemical properties of glass that can be analyzed forensically. Specific techniques mentioned include refractive index testing, density determination, microscopic analysis of fractures, and elemental analysis. The document also discusses how analysis of glass evidence can help reconstruct crime scenes and connect suspects to crimes by matching glass fragments.

1. SUBJECT NAME – INTRODUCTION TO FORENSIC
SCIENCE (IFS)
STUDENT NAME – MUDASSAR PINJARI

2.  glass is reasonably hard, transparent or
translucent material composed of fused inorganic
materials, primarily of silicon dioxide (sand)
 Glass is super cooled liquid, amorphous in nature.
 It found in many shapes, size ,colour and types.
 The wide variety of chemical compositions can alter
its characteristics.

5. Laminated glass
 Laminated glass is found in automobile
windshields.
 Basically, it is two separate panes of plate glass
adhered together with a clear laminated layer.
 It was designed to reduce injuries to passengers
in cases of accidents

6. • Tempered glass/ safety glass
 Tempered glass is a single pane glass that is
durable and difficult to fracture due to its
significant surface tension.
 When enough force is applied to break this surface
tension the entire pane of glass fractures into
thousands of small pieces (dicing).
 It is made stronger than ordinary glass by
introducing stress through rapid heating and
cooling of glass surface.

7. Terminology -
• Radial cracks are fractures extending outward from the point of impact.
• Concentric cracks are fractures forming in an approximately circular pattern around
the point of impact. They are usually in straight segments that terminate in an
existing radial crack.
• Cone or crater (Hertzian cone) is a funnel-shaped area of damage caused by a high-
velocity impact.
• Wallner lines (ridges) are rib-shaped marks with a wave-like pattern. Wallner lines
are called rib marks or ridges or conchoidal marks to describe their shape and are
almost always concave in the direction from which the crack was propagating
.
• 3R Rule- Radial cracks form a Right angle on the Reverse side of the force.
• Hackle is a line on the crack surface running parallel to the local direction of crack
spreading.

8. A) Low-velocity impact fractures
 Low-velocity projectiles produce cracks in the glass, which
radiate outward from the point of impact (radial cracks).
 If a pane is firmly held on all sides, concentric cracks can
form around the point of impact.
 By observing the Wallner lines (ridges) on the radial cracks,
the direction of breaking force can often be determined.
Observe only the Wallner lines on the radial cracks nearest
the point of impact.

9. B) High-velocity impact fractures
 A high-speed projectile striking a piece of glass will produce a cone or
crater.
 If the projectile passes through the glass, the opening on the exit side
will be larger than the opening on the entry side.
 The size of the hole and the diameter of the crater cannot be used to
reliably predict the size of the projectile.
 Projectiles that pass through the glass at an angle to the surface
produce an elongated hole.
 Radial cracks may also develop from high-velocity impact.

10. C) Thermal fractures
 In non-tempered glass a typical heat crack is curved, has a smooth
edge, and has no indication of the point of origin of the crack.
 If a pane of glass has been cracked by the action of heat, it shows
characteristic long wavy fractures.
 When glass is exposed to fire, it begins to melt at about 1200 degree
Fahrenheit. It becomes runny at about 1600 degree Fahrenheit.
 Glass that contains many cracks indicates a rapid heat build-up.
 Glass that is heavily stained indicates a slow, smoky fire.

11. Mechanism of glass
fracture

13. • After a striking force, glass first bends in the direction of applied force due to
elasticity.
• When the elastic limit exceeds, glass begins to crack beginning with the formation
of a radial crack or fracture on the surface opposite to the penetrating force.
• As the stress on the glass continues, concentric fracture form on the front surface
(surface where penetrating or striking force applied) of the glass.
• Fracturing continues with alternating radial and concentric fractures until the
process ends.
• When the first radial fracture begins, stress occurs along the edges closest to the
point of impact, and the stress lines form called conchoidal fractures.
• Conchoidal marks are shaped like arches. On the one side of the radial edge (near
the point of impact), the rib marks form right angles i.e. perpendicular with the
edge and nearly parallel to the opposite edge.
• Since these conchoidal marks form right angles opposite the side from where the
force is applied, they are useful to determine the direction of the applied force (3R
Rule).

14.  Forensic glass analysis
 A comparison of two or more glass fragments in an
attempt to determine if they originated from
same/different source(s).
 Glass evidences provides class as well as
individual characteristics

15. Physical properties
(colour,thickness)
Optical properties
(index or density) refractive
Elemental analysis
SEM
LA
ICPMS LIBS
XRF ICP
End of
analysis
End of
analysis
End of
analysis
NO
NO
NO
YE
S
YE
S
YE
S
MATCH
MATCH
MATCH
Write
report
METHODOLOGY
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16. Forensic glass examination has a well-established
analytical pathway. First, glass fragments are
recovered, observed, and identified by microscopy,
usually using a stereomicroscope prior to cleaning.
To examine the physical shape and colour of glass
fragments.
To examine a surface on a fragment.
To examine other trace evidences such as fingerprints
, hair, blood, fibers , etc.
MICROSCOPIC EXAMINATION

17. COLOUR
Colour may be used for purely aesthetic or for
technical reasons.
Comparing colour can distinguish between two or
more sources of glass.
side-by-side comparisons should be made with
fragments of approximately equal and sufficient
size.
The fragments should be visually compared on
edge, over a white surface, using natural light.
LIMITATION: the fragments usually are too small
and their colour density is too low, so it is not
possible to perform colorimetry.
Colourant Glass colours
Iron Green, brown,
blue
Manganese Purple
Chromium Green, yellow,
pink
Copper Blue, green, red
Cobalt Blue, green, pink
Nickel Yellow, purple
Uranium Yellow, brown,
green
Titanium Purple, brown
Carbon and
sulphur
Amber, brown
Antimony
sulphide
Red
Selenium Pink, red

18.  physical examinations could easily corroborate the presence of glass materials vs
other transparent materials.
 These observations are made in the preliminary stages of the analysis.
 The physical examination of glass can provide important information such as:
Type of impact that caused the fracture of glass, e.g. a fracture caused by a
gunshot, body impact, or by a hard object such a tool or bat.
1. Direction of the force, e.g. to establish if a window was broken from inside or from
outside.
2. Type of material, which may be very useful to corroborate or invalidate alibi i.e.
whether the glass is a flat architectural window, a tempered glass, a headlamp, or a
container.
3. Source of origin of the glass fragment, e.g. physical fit.
4. Glass appearance (fresh v/s scratched and dirty pieces may be important to
determine whether or not the glass transfer was recent, which is particularly
important in the transfer of glass to shoes).
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19. 1. Physical Fit
• A physical fit or physical “match”
requires the edges of one fragment to
perfectly fit into an edge of another ,
much like a jig-saw puzzle.
(Almirall,2001).
• The match of pieces of glass is three
dimensional and the analyst should
document the details by aims of
photography .
• The match should also be observed
under the microscope in order to
determine microscopic match of marks
(striations, impressions, etc.).
Figure. Photography of a physical match
between a known fragment of glass and a
questioned fragment of glass.
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20.  In cases where glass is recovered as a
fragment that present the full thickness
(original surfaces), it may be useful to
measure the thickness of the glass.
 The thickness measurements can provide
information about the possible type of
object from where it comes, i.e. a vehicle
side window , tempered glass, beverage
bottle.
 To measure thickness, a micrometer or
caliper with a precision of +/- 0.02mm or
better should be used.
 When two glasses show significant
differences in thickness, as determined by
the variation in the known-source glass,
they can be eliminated as originating from
the same source.
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Figure. Micrometer.

21.  Density(D) is defined as the ratio of mass(M) to volume(V).
 D = M/V (g/ml)
 Density in glass can be assessed either quantitatively by direct measurement or
qualitatively by simultaneous comparison of two or more specimens.
 Density is a function of chemical composition and atomic arrangement, which are
controlled by the composition of the batch and the cooling history of the glass,
respectively
 Accurate density measurements require a sample that is two to three millimeters
in diameter
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22. PRINCIPLE: ‘solid particles will either float, sink or remain suspended in a liquid
depending on its density relative to the liquid.’
 Standard/reference glass particle is immersed in a mixture of bromoform and
bromobenzene
 composition of mixture is adjusted until the glass chip remains suspended
 At this point (match point), the glass chip and the mixture have same density
 Glass chips of approximately the same size and shape as that of the standard are
added to the liquid
 Liquid is transferred to the density meter
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23. 23
•The mass of the pieces of glass(M) is determined using suitable weight
balance.
•The glass is then added to a graduated cylinder containing a previously
measured volume of water(V1).
•After addition, the volume in the graduated cylinder is recorded again(V2).
•Using the below formula, density of the glass fragment can be determined.
Density(D)=M/(V2-
V1)

24.  Refractive index is defined by Snell’s law as the ratio of the wave velocity in a
vacuum to the wave velocity in the transparent medium.(Stoiber and Morse 1981).
 RI=VVACUUM / VGLASS
 RI is dependant on:
1)the wavelength of light
2)the temperature of the medium
 Refractive index (RI) is unitless
 RI is a function of chemical composition and atomic arrangement
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25. Significance of glass and glass
fracture evidences
• To aid reconstruction of crime
scene
• To provide information about the
events which took place, and
assisting in proving or disproving a
witness’s story.
• Glass fracture patterns are
associated with burglary, criminal
mischief, shooting incidents, and
fire scenes.
• To evaluate the direction of
impact force applied (from inside
out or outside in).
• To calculate approximate force of
impact, angle of impact of force.
• To determine the type of glass
fracture, the sequence of firing,
direction of firing, and the type of
firearm for the projectile holes
present.

26. 1. Craig Elliott Kalani,
February.
On a dark, cloudy night in February, at 9:30 pm, a 19-year-old named Craig Elliott Kalani went
for a walk with his dog in his neighbourhood but he never returned because a hit and run driver
killed him. Pieces of glass were found on Craig's jacket and around his body at the crime scene.
These pieces of glass helped crime scene investigators figure out what happened.
Police searched for a vehicle that had the same damage as the hit and run car. Then they found a car
with those damages that belonged to Susan Nutt. In order to connect Susan's car to the glass
fragments found at the crime scene to the glass on her car, refractive index tests needed to be done.
This job was done by researchers at Oregon State University's Radiation Center. The scientists there
found that the windshield glass contained the same 22 chemicals as the ones in Susan's car. They
also said that both samples of glass were a definite match.
The glass evidence helped convict Susan Nutt. She failed to perform duties of a driver for an
injured person. She was sentenced to 5 years in jail.
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