Glass is an amorphous solid which is widely found as an evidence in the scene of crime. Glass holds significant forensic significance due to its prevalence at crime scenes and its ability to provide valuable evidence. Analysis of glass fragments, fracture patterns, and composition can help determine the sequence of events, source of impact, and even link suspects to a crime. This presentation consist of the types of glass encountered and it's forensic analysis.

1. GLASS
and it’s Forensic Analysis.
SHATTERING DOUBT, REVEALING CERTAINTY
By-
Adrita Dam.

2. INDEX
SL.
NO.
TOPIC
01. What is Glass?
02. Manufacturing of Glass (Different Types of Glasses and their
Compositions, Purpose and Application)
03. Forensic Significance of Glass
04. Collection and Preservation of Glass as Evidence

3. What is Glass?
Introduction:
• It is an amorphous solid structure. Typically transparent and brittle in nature.
• Also known as a Super-Cool Liquid as it is immediately cooled of before it is turned into a crystalline-
structured solid.
• The composition of Glass is mainly that of silica (silicon oxide)- additives like soda ash (sodium
carbonate), lime (calcium oxide) are added to change the properties like brisance and tensile strength
of the glass.
• Glass comes in various shapes and sizes and are used for various commercial production like cutlery
set, bottle. Window pane etc.

4. Types of Glasses:
1.Commercially used: Float Glass
2.Glassware: Soda-Lime glass,
Borosilicate Glass
3. Safety Glasses: Polycarbonate, Trivex
4. Prescription Eyeglasses: Plastic, Metal
Alloys
5. Sunglasses: Acrylic, Polarized Lenses
6. Electronic Appliances: Tempered Glass
7. Specialized Glasses: Optical Glasses,
Solar Glasses, Display Glasses

5. COMPOSITION AND APPLICATION OF
VARIOUS TYPES OF GLASSES.

6. Soda-Lime Glass
• It is composed of about 75% Silica
(Silicon dioxide), 15% Soda (Sodium
Carbonate), and 10% Lime (Calcium
oxide).
• It is used in making of Glass-panes,
Bottles, Containers, Tableware

7. Borosilicate Glass
• It is composed of about 80% silica and 13%
boron trioxide.
• It has a higher melting point and lower
coefficient of thermal expansion.
• Used in laboratory glassware, cookware, and
high-quality glass lighting fixtures

8. • It contains a significant amount of Lead Oxide
(PbO) along with Silica and other additives.
• The Lead content gives the glass brilliance and
a higher refractive index.
• Its high refractive index makes it desirable for
creating sparkling and intricate designs.
• Lead glass is renowned for its optical properties
and is often used for making fine glassware,
including luxury glassware, decorative items,
and chandeliers.
Lead Azide Glass / Crystal

9. TEMPERED GLASS:
• Tempered glass is made from soda-lime glass but undergoes a
thermal tempering process. It is heated to a high temperature and
then rapidly cooled, creating internal stresses that strengthen the
glass.
• Tempered glass is highly durable and resistant to mechanical
stress, making it suitable for safety applications.
• It is used in automotive windows, shower doors, mobile phone
screens, and architectural applications where safety and impact
resistance are crucial

10. • Laminated glass consists of multiple layers of
glass with an interlayer of polyvinyl butyral
(PVB) or ethylene-vinyl acetate (EVA)
sandwiched between them.
• Laminated glass offers enhanced safety and
security. When broken, the interlayer holds the
shattered glass together, reducing the risk of
injury.
• It is used in windshields, skylights, bullet-
resistant glass, and soundproofing applications.
LAMINATED GLASS:

11. Fibre Glasses:
• Fibre glass, or Glass Fibres, are composed of fine
fibres of glass reinforced with a polymer resin.
• The glass fibres are typically made from silica, with
additives to improve strength and flexibility.
• Fibre glass has excellent insulation and strength-to-
weight ratio properties.
• It is widely used in insulation materials, composite
materials, automobile parts, temporary roofs/shades,
boats, and aerospace applications.

12. Specialized Glasses

13. • Optical glass contains specific materials
to achieve precise optical properties
like great resolution, clarity, blue lens
etc.
• These glasses are used for lenses,
prisms, and optical instruments.
OPTICAL GLASSES

14. SOLAR GLASSES:
Solar glass is designed to maximize light
transmission and minimize reflection in solar
panels, allowing efficient conversion of sunlight
into electricity.

15. DISPLAY GLASSES:
• Display glass, like Corning's Gorilla Glass, is
chemically strengthened to resist scratches and
damage, making it suitable for smartphones, tablets,
and electronic displays

16. Forensic Significance of Glass

17. • -The forensic significance of glass lies in its ability to
provide crucial evidence in criminal investigations.
• -Glass fragments or residues can often be found at crime
scenes, and analysing them can provide valuable
information to help determine the sequence of events,
identify sources, and link individuals to the crime.
Here are some key aspects of the forensic
significance of glass----

18. Trace Evidence:
Glass fragments or residues can be left behind at
crime scenes, on clothing, tools, or weapons used
in the commission of a crime. These trace pieces
can serve as crucial evidence linking suspects to
the scene.
Transfer of Glass:
When objects come into contact with glass surfaces,
glass particles can transfer between them. These
transfers can occur during crimes such as burglaries,
break-ins, or vehicle accidents.
Glass Transfer and Trace Evidence:

19. Glass Fracture Patterns
and Reconstruction:
- Fracture Patterns: Glass fractures in
distinct patterns depending on the type of
force applied, such as impact, bending, or
heat. Analysing fracture patterns can help
determine the direction and sequence of
events during a crime.
- Reconstruction:
By fitting glass fragments together, forensic
experts can reconstruct the original object or
determine the type of glassware involved.
This reconstruction can aid in identifying
the source of the glass and provide valuable
information for investigations.

20. Refractive Index and Comparison:
Immersion Method: Forensic scientists can use the immersion
method to measure the refractive index of glass fragments. By
matching refractive indices, they can determine if the
fragments share a common origin.
Refractive Index: Glass has a unique refractive index, which
is the measure of how light bends as it passes through the
material. Comparing the refractive index of glass fragments
found at a crime scene to that of known samples can help
establish if they originated from the same source.

21. Glass Composition andSource Determination:
- Elemental Analysis: Analysing the elemental composition of glass fragments through techniques like
scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) can provide insights
into its chemical makeup. Different glass compositions can help identify the type and origin of the glass, such
as window glass, automotive glass, or specialty glass.
- Database Comparison: Comparing the elemental composition of glass fragments to a database of known
glass samples can assist in narrowing down potential sources and identifying manufacturers or specific types
of glass.

22. Glass as Forensic Toolmarks:
Glass Toolmarks: Glass can retain impressions from tools used to break or manipulate it. These toolmarks can be
analysed and compared to the tools recovered from a suspect or crime scene, potentially establishing a link between the
tools and the crime.
The forensic significance of glass lies in its ability to provide valuable evidence such as transfer patterns, fracture
analysis, refractive index matching, composition analysis, and toolmark impressions. By analysing glass fragments and
residues, forensic experts can contribute to crime scene reconstruction, source determination, and linking individuals to
criminal activities.

23. Collection and Preservation of Glass:
-Collection and preservation of glass as evidence is a crucial aspect of forensic investigations.
Glass fragments, residues, or objects found at crime scenes can provide valuable information and link
suspects to the scene.
-Proper collection and preservation techniques are essential to maintain the integrity and evidentiary value
of the glass evidence.

24. 1. Safety Precautions:
- Safety Gear: Investigators should wear
appropriate personal protective equipment
(PPE) such as gloves and safety goggles to
avoid contamination and injury.
- Avoid Cross-Contamination: To prevent
cross-contamination, investigators should use
clean tools and packaging materials for each
separate glass item.

25. 2. Documenting the Scene:
- Photography and Sketches: Before
collecting any glass evidence, document the
scene by taking overall and close-up
photographs. Make sketches or diagrams to
accurately depict the location and orientation
of glass fragments or objects.

26. 3. Collection Techniques:
- Tweezers or Forceps: Use clean, non-magnetic tweezers or
forceps to carefully pick up glass fragments, taking care not to
exert excessive pressure that could alter their shape or cause
breakage.
- Packaging: Place each glass fragment or object in a separate
clean container or envelope. Clear plastic bags or small, sealable
containers are commonly used for glass evidence. Ensure proper
labelling with the case number, date, location, and a description of
the item.

27. 4. Preventing
Cross-Contamination:
- Tools and Packaging: Use clean tools for each
separate glass item to avoid cross-contamination.
For packaging, ensure separate containers or
envelopes are used for each distinct glass
fragment or object.
- Disposable Gloves: Change disposable gloves
between handling different glass items to prevent
contamination.

28. 5. Preservation andTransportation:
- Fragile Glass Fragments: Fragile or small glass fragments
should be packaged with care to prevent further damage.
Place them in a padded container or envelope to minimize
movement during transportation.
- Larger Glass Objects: For larger glass objects, wrap them
in protective material such as foam or bubble wrap to
prevent scratching or breakage during transit.
- Proper Labelling: Clearly label each package with the
case number, exhibit number, description, and the name of
the collector. Ensure the containers are sealed securely to
prevent tampering or loss.

29. 6. Chain of Custody:
- Documentation: Maintain detailed records of the collection, packaging, and transportation of
the glass evidence. This includes documenting who collected the evidence, when and where it was
collected, and who had custody of it at all times.
- Secure Storage: Store glass evidence in a secure, controlled environment to prevent damage or
loss. It should be kept away from extreme temperatures, humidity, and potential contaminants.

30. 7. Submitting to the Laboratory:
- Contact the relevant forensic laboratory for
specific instructions on submitting glass evidence.
Follow their guidelines for packaging, labelling, and
any additional documentation required.
- Provide a detailed chain of custody record along
with the glass evidence to ensure its integrity and
admissibility in court.
Proper collection and preservation of glass evidence
are essential to maintain its evidentiary value.
Following these guidelines helps ensure the integrity
of the evidence, facilitates accurate analysis, and
enhances its reliability in the investigative process
and potential legal proceedings.

31. REFERENCE
1. Almirall, J. R., Trejos, T., & Lambert, K. (2020). Interpol review of glass and paint evidence 2016-2019.
Forensic Science International: Synergy, 2, 404–415. https://doi.org/10.1016/j.fsisyn.2020.01.010
2. Interpretation of Glass Evidence - Handbook of Trace Evidence Analysis - Wiley Online Library
3. Forensic Examination of Glass and Paint | Analysis and Interpretation (taylorfrancis.com)
4. Glass material and their advanced applications (researchgate.net)