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  • 1. 4/19/2013 saurabh bhargavaGood morning ma’m & frndz.. 1
  • 3. CONTENTS 4/19/2013• Glass definition• Types of glass saurabh bhargava• General properties of glass• Scope of glass examination• Types of cracks and fractures in glass samples and their interpretation• Forensic examination of glass samples 3
  • 4. SCOPES• Glass, as a physical clue, is frequently encountered in various crimes; such as 4/19/2013 burglary, road accidents, murder, sexual assaults, shooting incidents, arson and saurabh bhargava 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 may 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 weapon. 4
  • 5. CONTINUE… 4/19/2013• Whenever there is violence, bottles, window pane glass, mirrors, eye glasses and other glass objects can be accidently scattered and saurabh bhargava fragments of these can also adhere to the criminal’s clothing or shoes.• Thus, glass forms one of the evidentiary materials in many criminal investigations. 5
  • 6. GENERAL•Glass can be found in most localities. It is produced in a 4/19/2013wide variety of forms and compositions.•It can occur as evidence when it is broken during the saurabh bhargavacommission of a crime.•Broken glass fragments ranging in size from large piecesto tiny shards may be transferred to and retained bynearby persons or objects.•The mere presence of fragments of glass on the clothingof an alleged burglar in a case involving entry through abroken window may be significant evidence if fragmentsare found.•The significance of such evidence will be enhanced if thefragments are determined to be indistinguishable in 6allmeasured properties from the broken window.
  • 7. 4/19/2013 saurabh bhargavaPRIMARY TRANSFERSECONDARY TRANSFER 7
  • 8. NUMBER OF GLASS FRAGMENTS THAT CAN BETRANSFERRED IS CONTROLLED BY A NUMBER OFFACTORS: 4/19/2013•The closer something is to the breaking glass, themore likely it is to have glass fragments transferred to saurabh bhargavait.The number of fragments transferred decreases withdistance from the break (Pounds and Smalldon 1978).•The person breaking a window will have more glasson him or her than a bystander, and the more blowsrequired to break out the glass, the more glass thatwill be transferred (Allen et al. 1998b).•The number of glass fragments generated by abreak is independent of the size and thickness of thewindow but increases with greater damage to the glass(Locke and Unikowski 1992). 8
  • 9. RECOVERY OF GLASS FRAGMENTS FROMCLOTHES BY A FORENSIC EXAMINER DEPENDSUPON ADDITIONAL FACTORS: 4/19/2013 saurabh bhargava •Less glass is retained on slick clothing, such as nylon jackets, than on rough clothing, such as wool sweaters. •Wet clothing retains more glass than dry clothing. •Glass fragments fall off clothing over time, and larger pieces fall off before smaller pieces. •Glass falls off faster if the person wearing the clothing is active. 9
  • 10. GLASS 4/19/2013 Glass is technically defined as saurabh bhargava “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 10
  • 11. • An extended, 3D network of atoms which lacks the repeated, orderly arrangement 4/19/2013 typical of crystalline materials. saurabh bhargava• Glass is made by heating silica sand with sodaand lime--and sometimes other materials--to amolten mass, then cooling it so quickly thatthere is no time for crystals to form in the glass. 11
  • 12. 4/19/2013•Even though glass is aliquid, to us it appears solidit is not viscous like other saurabh bhargavaliquids, but it looks rigid.•The viscosity is such a highvalue that the amorphousmaterial acts like a solid. 12
  • 13. COMPONENTS 4/19/2013Formers– forms the glassy, non-crystalline structure saurabh bhargavafluxes– improve melting properties but impart lowchemical resistance• typically alkali or alkaline earth oxidesmodifiers (stabilizers or intermediates)– a material that improves stability• typically oxides of Ca, Al, or Zn 13
  • 14. COMPONENTS 4/19/2013• Formers: SiO2, B2O3, P2O5, GeO2, V2O5, As2O3 saurabh bhargava• Fluxes–Softeners [lowers melting point]: Na2O, K2O, LiO, Al2O3, B2O3, Cs2O• Stabilizers–Chemical/Corrosion Resistance: CaO2, MgO2, Al2O3, PbO2, SrO, BaO, ZnO2, ZrO 14
  • 15. TYPES OF GLASS 4/19/2013A)On the basis of manufacturing process:  Ordinary sheet glass saurabh bhargava  Float glass(plate)B) On the basis of composition:  Oxide glass  Non oxide glassC)On the basis of market application:  Commercial/soda lime glass  Lead glass  Borosilicate glass  Laminated glass  Tempered glass 15
  • 16. 4/19/2013 saurabh bhargava 16ROLLED AND FLOAT GLASS
  • 17. TEMPERED AND LAMINATED GLASS 4/19/2013 saurabh bhargava 17
  • 18. BORO-SILICATE AND LEAD GLASS 4/19/2013 saurabh bhargava 18
  • 19. SOME SPECIAL TYPES OF GLASS 4/19/2013• Glass fibre• Vitreous silica saurabh bhargava• Alumino-silicate glass• Alkali-barium silicate glass• Glass ceramics• Technical glass• Phosphate glass• Optical glass• Sealing glass 19
  • 20. GLASS FRACTURE 4/19/2013• When force is applied on any surface of glass it bends but since the elasticity of glass is limited ultimately, it gets fractured after the saurabh bhargava threshold force application.• An investigator often has to decide wheather a pane of glass was broken from outside or from inside, wheather it was broken with a bullet or with a blunt object. 20
  • 21. IMPACT OF FORCE ON GLASS 4/19/2013e Impact causes a pane of glass to bulge saurabh bhargava – Side opposite the impact will stretch more & rupture first Radial cracks are rapidly propagated in short segments from the point of impact 21
  • 22. RADIAL AND CONCENTRIC CRACKS 4/19/2013  Elasticity permits bending until radial cracks form on the opposite saurabh bhargava side of the force  Continued force places tension on the front surface (force side), forming the concentric cracks 22
  • 23. TYPES OF CRACKS 4/19/20131) Radial cracks: When an object has been thrown through a saurabh bhargava glass 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. 23
  • 24. RADIAL AND CONCENTRIC CRACKS 4/19/2013 saurabh bhargava Concentric 24 Radial fracture fracture
  • 25. 4 R RULE 4/19/2013Ridges on Radial cracks are at Right saurabh bhargava angles to the Reverse side of impact. 25
  • 26. TYPES CONTINUE.. 4/19/20132)Concentric cracks: saurabh bhargava A series of broken circles originate on the surface, on which force is being applied around the point of impact. These are the secondary fractures as they always appear after radial fractures. 26
  • 27. TYPES CONTINUE… 4/19/20133)Cone fractures: When a high projectile(like bullet), penetrates the saurabh bhargava glass, it makes a round crater shaped hole. It is surrounded by radial & concentric cracks. The hole is usually wider on the exit side and gives appearance like a cone. Thus the narrower side of a cone fracture indicates the direction from which the bullet entered. 27
  • 28. CONE FRACTURES 4/19/2013 Fracture by high speed projectile saurabh bhargava 28
  • 29. FRACTURE BY BULLET 4/19/2013 When a bullet is travelling at high saurabh bhargava velocity the opening on the reverse side of impact will be larger 29
  • 30. SIGNIFICANCE AND USE OF STUDY OF GLASS FRACTURES 4/19/2013• Fracture patterns are unique; Pieces from the broken glass pane or hole often show saurabh bhargava marks that are characteristics of the type of injury and direction of force. If correctly interpreted, these findings gives useful information about the object used for breaking and velocity of breaking object. Fracture examinations can provide information as to the direction of the breaking force and the sequence of30 multiple impacts.
  • 31. DETERMINATION OF THE DIRECTION OF FORCEIN BREAKING A WINDOW PANE: 4/19/2013 saurabh bhargava -direction of the rib marks [stress marks on broken edges of glass that are perpendicular to one side of glass] For radial fractures (radiating from the center): - the direction of the force is on the same side as the tangential 31 parts of the rib marks
  • 32. 4/19/2013 saurabh bhargavaPROPAGATION OF FRACTURES DUE 32TO MULTIPLE IMPACTS
  • 33. Which fracture occurred first? 4/19/2013 saurabh bhargava 33
  • 34. POINTS TO REMEMBER WHILE ANALYZING GLASS FRACTURES 4/19/2013✓Radial cracks are formed first, commencing on the sideof the glass opposite to the destructive force saurabh bhargava✓Concentric cracks occur afterward, starting on thesame side as the force✓As the velocity of the penetrating projectile decrease,the irregularity of the shape of the hole and of itssurrounding cracks increase✓Fracture always terminates at the existing line fracture 34✓Stress marks occur on the edge of a radial glassfracture.
  • 35. CONTINUE… 4/19/2013 ✓Stress marks run perpendicular to one edge and parallel to the other edge of glass. saurabh bhargava ✓Stress’ perpendicular edge is always located opposite from which the force of impact occurred. ✓Concentric fractures, the perpendicular end always faces the surface on which the force originated. ✓Radial cracks form a Right angle on the Reverse side of the force (4 R rule). 35
  • 36. RESULTS POSSIBLE FROM LABORATORY EXAMINATION OF GLASS 4/19/2013•If the pieces of broken glass can be made to fit together inthe manner of a jig-saw puzzle, positive association can bemade. saurabh bhargava•Even glass fragments as small as the head of a pin can becompared. However, even if unusual properties are present,only a strong indication of common origin can be given, notan absolute identification.•If a window has been struck with a blunt instrument suchas a rock, stick or fist, it is possible to determine the side ofimpact and the nature of the force involved.•If a window has been penetrated by a bullet, it is possibleto determine the direction from which it was fired. 36•If two or more bullet holes are in close proximity, it ispossible to determine the sequence of firing
  • 37. OBJECTIVES 4/19/2013 To be able to identify, classify & individualize the piece/pieces of glass fragments found at suspect/victim’s clothing or at crime scene and to saurabh bhargava use it, if possible, as an element to aid reconstruction of events or as an evidence to prove/disprove….. 37
  • 38. GLASS ANALYSIS 4/19/2013 # Visual Inspection of Known/ Questioned for saurabh bhargava Fracture Matches # Comparison of Glass: •Physical Properties •Optical Properties •Chemical Properties # Classification of Glass into End Use Category # Discrimination between glass samples 38 # Interpretation and Value of Results
  • 39. PROBLEM TO BE SOLVED??? 4/19/2013Classification: saurabh bhargavaThe ability to use some measured characteristics of aquestioned object to place it into a product use class.Discrimination:The ability to distinguish between two or more objectswithin the same product use class. 39
  • 40. SEQUENCE OF EXAMINATION/ANALYSIS 4/19/2013 saurabh bhargava •First of all physical properties are assessed. •optical properties of the specimens are measured next. •Chemical composition of the glass is typically measured last. 40
  • 41. FORENSIC GLASS EXAMINATION 4/19/2013 •A forensic glass analysis is typically a comparison saurabh bhargava of two or more glass fragments in an attempt to determine if they originated from different sources. •These analyses require the determination of class characteristics that may associate objects with a group of similar objects such as containers, but never to a single object. •Only physically matching of two or more broken glass fragments allows for their association with 41 each other to the exclusion of all other sources .
  • 42. POINTS TO REMEMBER…. 4/19/2013•Every analytical test available is not alwaysperformed on each specimen.•The aim of a comparative glass analysis is to exclude saurabh bhargavapossible sources. When a difference is detected, nofurther comparison is necessary.•It is not always possible to assess every potentialpoint of comparison in each glass specimen.•A glass fragment may be too small to be analyzedwith reproducible results even when a feature ispreserved.•Consequently, the actual tests performed on a set ofspecimens depend on the size and shape of the glass 42fragment, as well as analytical considerations.
  • 43. PLASTIC IDENTIFICATION AND SN SURFACE 4/19/2013 saurabh bhargava  Plastic can be eliminated by testing for indentation by a needle point.  Fluorescence upon short wave (254nm) illumination of an original surface can detect the Sn contamination on one side of float glass. 43
  • 44. TABLE SALT & GLASS SAMPLE 4/19/2013  Table salt can be differentiated by saurabh bhargava their shape; they are crystallized particles and thus have a regular and ordered shape unlike glass which is amorphous and has an irregular shape. 44
  • 45. PHYSICAL MATCHING 4/19/2013 This is most conclusive proof of source correspondence, since no two fractures will saurabh bhargava ever be identical over any appreciable length. A complimentary lateral fit along the broken edges over a length of quarter inch (1/4) or more establishes that the two glass fragments were continuous before breakage. 45
  • 46. INITIAL EXAMINATION 4/19/2013 The physical properties used for comparison include glass saurabh bhargava color, fluorescence, thickn ess, surface features, and curvature, observance of conchoidal fracture, determination of hardness, reaction to a hotpoint, microscopy. 46
  • 47. “BUGS”-DOT NUMBERS ON VEHICLE GLASS 4/19/2013 saurabh bhargava 47
  • 48. “BUGS”-DOT NUMBERS ON VEHICLE GLASS 4/19/2013 saurabh bhargava 48
  • 49. COLOR 4/19/2013Materials can be added to the batch toproduce glass in practically any color. saurabh bhargavaImpurities present in the raw materialsused to produce glass can impartunintentional color.Differences in color represent a changein glass chemistry and can be used todifferentiate specimens. 49
  • 50. COLOR CONTINUE.. 4/19/2013 Typically not possible to reliably perform colorimetry on glass fragments in forensic casework due to too small saurabh bhargava size and too low color density of samples. Color assessment is performed visually against a white background in natural light with the particle on edge. Side-by-side comparison should be used with similarly sized particles. 50
  • 51. DETECTION OF CURVATURE 4/19/2013 An Interferometer can be used to detect the most minimal curvature on the glass saurabh bhargava surface. Curvature indicates possible sources: •windshield •containers •other non-flat glass source 51
  • 52. CURVATURE: 4/19/2013 A spherometer is used to measure the radiusof curvature of the glass fragments having curved surface. saurabh bhargavaThe radius of curvature of the fragment is calculatedusing the formulae. R= (l2/6h)+(h/2)Where 1 = the mean distance between the legs ofthe spherometer. h = height of the curved surface 52
  • 53. FLUORESCENCE•fluorescence can be used as a basis to 4/19/2013differentiate glass specimens.•The glass surface that was in contact with the tin saurabh bhargavabath during the manufacturing procedure willfluoresce when exposed to short-wave (~254 nm)ultraviolet light.•Fluorescence examinations can also beperformed using fluorescence spectroscopy onspecimens as small as 0.05 mm2 .•Fluorescence on a glass surface will be detectedonly if the surface that will fluoresce is preserved,collected, and analyzed. 53
  • 54. THICKNESS CONSIDERATIONS 4/19/2013 Tempered glass is greater than 3.0 mm thick saurabh bhargava Vehicle side windows are typically 3.3-3.6 mm thick 54
  • 55. DENSITY 4/19/2013The ratio of the mass of an objectto the volume occupied by that object saurabh bhargava– g/cm3 (solids); g/mL (liquids)d = m/VDensities of solids & liquids areoftencompared to the density of water– sink or float 55Varies with temperature
  • 56. DENSITIES OF VARIOUS GLASSESAND RELATED MATERIALS: 4/19/2013 Window glass, flat- 2.47 to 2.56 saurabh bhargava Head light glass- 2.47 to 2.63 Mica- 2.6 to 3.2 Quartz- 2.65 Glass, flint- 2.9 to 5.9 Diamond- 3.01 to 3.52 56
  • 57. GLASS DENSITY CAN BE MEASURED BY: 4/19/2013 Displacement method saurabh bhargava Floatation method Density gradient column method 57
  • 58. REFRACTION The bending that occurs when a light 4/19/2013 wave passes at an angle from one medium to another (air to glass) saurabh bhargava – bending occurs because the velocity of the wave decreases 58
  • 59. REFRACTIVE INDEX (ND) 4/19/2013 •The ratio of the velocity of light in a vacuum to the velocity of light in a given saurabh bhargava 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 59 frequency
  • 60. R I OF COMMONLY ENCOUNTERED GLASSES 4/19/2013 Automobile head light 1.47 – 1.49 glass saurabh bhargava Bottles 1.51 – 1.52 Window glass 1.51 – 1.52 Opthalmic glass 1.52 – 1.53 60
  • 61. REFRACTIVE INDEX IS THE MOST COMMONLYMEASURED PROPERTY IN THE FORENSIC 4/19/2013EXAMINATION OF GLASS FRAGMENTS BECAUSE: saurabh bhargava •Precise refractive indices can be measured rapidly on the small fragments typically found in casework. •It can aid in the characterization of glass. •It provides good discrimination potential. 61
  • 62. METHODS TO CALCULATE REFRECTIVEINDICES OF QUESTIONED GLASS SAMPLES 4/19/2013Immersion Methods saurabh bhargava Becke line method, Dispersion staining methodEmmons Double Variation methodAutomated Method 62
  • 63. DENSITY MEASUREMENTS ARE PERFORMED LESSFREQUENTLY THAN REFRACTIVE INDEXDETERMINATIONS BECAUSE: 4/19/2013 •The glass fragment must be scrupulously clean saurabh bhargava and free of inclusions. •Accurate density measurements require a sample that is two to three millimeters in diameter. •density measurements required the use of hazardous liquids, such as bromoform. 63
  • 64. BECKÉ LINE METHOD (1892) 4/19/2013 •When the objective of the microscope is raised (focus saurabh bhargava up), a bright line moves into the direction of the material of higher R.I. •Once the line disappears or doesn’t move,the R.I. of the oil can be measured by a refractometer. •The Becké line is best observed with contrast microscopy. 64
  • 65. OIL IMMERSION AT THE MATCHTEMPERATURE 4/19/2013 saurabh bhargava 65
  • 66. ELEMENTAL ANALYSIS 4/19/2013Glass composition analysis can be used todifferentiate between: saurabh bhargavaglasses made by different manufacturers,glasses from different production lines of the samemanufacturer,glasses made over a period of time in a singleproduction line. 66
  • 67. GLASS COMPOSITION ANALYSIS IS PERFORMED INFREQUENTLY BECAUSE: 4/19/2013•Most methods of glass composition analysis aredestructive. saurabh bhargava•Most methods require glass samples larger than thoseroutinely encountered in forensic casework.•Most of the instrumentation used to measure glasscomposition is expensive to purchase and maintain, andmuch of the instrumentation has few other applications.•Because of the complexity of the calculations, Bayesianstatistical analysis including compositional data is 67extremely difficult to apply.
  • 69. TECHNIQUES USED FOR ELEMENTAL ANALYSIS Semi-quantitative quantitative techniques 4/19/2013  techniques  neutron activation analysis  flameless atomic absorption saurabh bhargava scanning electron spectrometry microscopy-energy  spark-source mass dispersive spectrometry spectrometry X-ray fluorescence  inductively coupled plasma- optical emission spectrometry  inductively coupled plasma- mass spectrometry  laser ablation-inductively 69 coupled plasma-mass spectrometry
  • 70. 4/19/2013 saurabh bhargava 70