Glass fracture

forensic importance of glass fracture and glass importance in the crime scene.

1. DEPARTMENT OF CRIMINOLOGY AND FORENSIC SCIENCE PRESENTATION ON –GLASS FRACTURE PRESENTED BY- ANJALI VISHWAKARMA ROLL NO.-Y19242503 DR. HARI SINGH GOUR CENTRAL UNIVERSITY SAGAR PRESENTED TO- DR. NAVJOT KAUR

2. CONTENT Glass definition Types of glass General properties of glass Scope of glass examination Types of cracks and fractures in glass sample and their interpretation Forensic examination of glass samples.

3. scopes Glass, as a physical clue, is frequently encountered in various crimes such as burglary, road accidents, murder, sexual assaults, shooting incidents, arson and vandalism. The chips of broken glass window may be lodged in suspect’s shoes or garments during the act of burglary/crime, particles of headlight glass found at the crime scene make offer clues that confirm the identity of a suspected vehicle, glass may also be found on the clothing of an alleged assailant, where a bottle is used as a weapon.

4. Whenever there is violence, bottles, window pane glass, mirrors, eye glasses and other glass objects can be accidently scattered and fragments of these can also adhere to the criminal's clothing or shoes. Thus, glass forms one evidentiary materials in many criminal investigations

5. Glass glass is technically defined as ‘’The inorganic product of fusion which has cooled to a rigid condition without crystallizing.’’ In contrast to crystalline solids which have an ordered internal arrangement of atoms ,the internal structure of glass consists of a network of atoms lacking long-range symmetry; This condition is referred to as the vitreous, or glassy, state.

6. An extended, 3-D network of atoms which lacks the repeated, orderly arrangement typical of crystalline materials. Quartz melt quartz glass Glass is made by heating silica and with soda and lime and something other materials to a molten mass, then cooling it so quickly that there is no time for crystals to form in the glass.

7. Even though glass is a liquid to us it appears solid it is not viscous like other liquids, but it looks rigid. The viscosity is such a high value that the amorphous material acts like a solid

8. CHEMICAL COMPOSITION OF GLASS Glass is a hard and crystalline substance which is super cooled liquid, tensile strength of glass depends upon chemical bonding of glass mainly includes oxides of various metals. They are- Network forming oxides Network loosing oxides Stabilizing oxides Intermediates oxides

9. NETWORK FORMING OXIDES Eg- SiO2, B2O3, As2O3, P2O5 They are also called “formers” They form network of glass.

10. NETWORK LOOSING OXIDES Eg- Na2O, CaO, MgO, BaO, K2O, LiO2 etc. They decreases the melting point of glass. They are also called fluxes – “softeners”.

11. STABILISG OXIDES Eg.-CaO, BaO,MgO etc. They decreases rate of hydrolysis. They are also called “modifiers’’

12. INTERMEDIATES OXIDES Eg.-Al2o3, Sb2O3, PbO, ZnO, TiO2, BeO etc. They plays role of modifiers and formers.

13. TYPES OF GLASS [A]. On the basis of manufacturing process: Ordinary sheet glass Float glass (plate) [B].On the basis of composition: Oxide glass Non oxide glass [C].On the basis of market application Commercial the basic of market application : Lead glass Borosilicate glass Laminated glass Tempered glass

14. Collection preservation of glass evidence Firstly photographed the glass piece found as a evidence on soc. Fingerprints are generally found on glass surface. Cases in which breaking of glass was done due to the result of struggle, probability of finding latent fingerprints is more in the surface of glass. Note done the presence of latent prints on the surface of glass and also the inner and outer surface of glass. This is important in the process of division and determination. For physical matching, it is necessary to collect the suspect object or artical from which the glass piece belongs to.

15. For packing, glass piece should always be wrapped in cotton or cloth. Minute piece of glass should be packed in pill box for edges, it should be sealed with wax or modeling clay so they can not destroyed otherwise contor matching is not possible. Detail should be refer after packing.

16. PHYSICAL AND CHEMICAL MATCHING CHEMICAL MATCHING-Laboratory examination of glass is based on comparison. PRELIMINARY EXAMINATION- Matching should be done of glass piece with its belong parts on the parameters of color, thickness, design, curvature, color comparison also done in uv light. COMPARISON OF DENSITY-Density of glass is 2.1-8.1 gm cm 3 whereas optical and crystal glass having their density much more in comparison to normal glass

17. FREE FLOATATION MOTHOD UV LIGHT METHOD NEEDLE SHAPE MICROSCOPE DENSITY GRADIENT COLUMN METHOD COMPARISON OF REFRACTIVE INDEX

18. SOME SPECIAL TYPES OF GLASSS Glass fiber Vitreous silica Alumino-silicate glass Alkali-barium silicate glass Glass ceramics Technical glass Phosphate glass Optical glass Sealing glass

19. GALSS FRACTURE By fracture direction of force of known Whenever any object collides with the glass with force then as a result cracks will develops in glass on it will break. FACTURE REDIAL FRACTURE CON CENTR IC FRACTURE FRACTURE BY HEAT

20. RADIAL FRACTURE When an object has been thrown through pane, a fracture forming a pattern somewhat like a spider web will be seen. The cracks will appear radiating outwards from the point of impact making a star shaped fracture known as radial fracture. The radial fracture originates on the surface opposite to that on which force was applied. This type of fracture is always the first to appear on glass.

21. Radial and concentric fracture

22. CONCENTRIC FRACTURE A series of broken circles originate on the surface, on which force is applied around the point of impact. There are the secondary fracture as they always appears after radial fractures.

23. Radial and concentric fracture

24. FRACTURE BY HEAT Fractures caused by excessive heat will not show regular radial and concentric fractures as the impact is not on one spot but will be in v-shape. The fracture will be dispersed and the glass will break into small fragment and fall on the side where the heat was applied or caused.

25. MARKS OF FRACTURES RIB MARKS HECKLE MARKS

26. RIB MARKS RIB MARKS-At radial fracture direction of the rib marks is the stress marks on broken edges of glass that are to one side of glass. For radial fractures (radiating form of centre), the direction of the force is on the same side as the tangential parts of rib marks. In this direction of collision was compressed and at opposite side will expanded.

27. HECKLE MARKS They are found between rib marks. If the impact occurred to the glass surface on the outside of the house , then the heckle marks would be at right angles to the glass surface on the inside of glass.

28. Forensic glass examination A forensic glass analysis is typically a comparison of two more glass fragments in an attempt to determine if they originated from different sources. These analysis requires the determination of class characteristics that may associate objects with a group of similar object. Only physically matching of two or more broken glass fragments allows for their association with each other to the exclusion of all other sources.

29. Refracti v e i n d e x : ( N D ) T h e r a t i o o f t h e v e l o c i t y o f l i g h t i n a v a c u u m t o t h e velocity of light in a given medium ND ( Water ) - 1.333 . i . e . light travels 1.333 time faster in vacuum than in water An intensive property varies with temperature and the light frequency

30. D e n s i t y measurements are performed less frequently than refractive index determination because T h e g l a s s f r a g m e n t m u s t b e scrupulously clean and free of inclusions accurate density measurements require a sample that is two or three mm in diameter .

31. B A C K E L I N E M E T H O D ( 1892 ) W h e n the objective of the microscope is raised , a bright line moves into the direction of the material of higher R.I . Once the line disappears or doesn't move , the refractive index of oil can be measured by a refract o m e t e r . t h e b a c k e line is b e s t observed with contrast microscopy .

32. REFERENCE FORENSIC SCIENCE IN CRIME SCENE INVESTIGATION(Third Edition) by B.S.NABAR Forensic interpretation of glass evidence by James Michael Curran Tacha Natalie Hicks Slide share.net/mobile https://www.journals.uchicajo.edu/doi/abs/10.1086/626840?journalcode=jg

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