Shattered: Forensic Glass Analysis

Bell Work for Tuesday, October Study for your test today!! Study for your test today!! Be sure to review on your ridge characteristics! Be sure to review on your ridge characteristics!

Bell Work for Friday, March 14 What are the different methods to find the type of glass from a crime scene? What are the different methods to find the type of glass from a crime scene? How do you know the entrance and order of bullet holes in glass? (see example below) How do you know the entrance and order of bullet holes in glass? (see example below)

CHE Physical Measurements Properties Properties Physical Properties; can be measured without changing the substance, i.e., color, density, melting point, etc... Physical Properties; can be measured without changing the substance, i.e., color, density, melting point, etc... Chemical Properties; the way a substance changes (reacts), i.e., combustion Chemical Properties; the way a substance changes (reacts), i.e., combustion Density Density

CHE Physical Properties Mass Measurements: Density Density Temperature Light Measurements: Color Color Refractive Index Refractive Index Birefringence Birefringence

CHE Matter; Measurement Density Density Amount of mass per unit volume Amount of mass per unit volume Measured in g/cm 3, or g/mL Measured in g/cm 3, or g/mL

CHE Matter; Measurement Temperature - based upon standard - melting and boiling points of water: Temperature - based upon standard - melting and boiling points of water: Fahrenheit (32° - 212°) Fahrenheit (32° - 212°) Celsius (0° - 100°) Celsius (0° - 100°)

CHE Matter; Measurement Temperature Temperature Algor Mortis - drop in body temperature after death. Algor Mortis - drop in body temperature after death. Generally follows linear drop to ambient temperature. Generally follows linear drop to ambient temperature. Depends upon ambient temperature, insulation (clothing), body size, activity, infection, drugs, physical shape, etc. Depends upon ambient temperature, insulation (clothing), body size, activity, infection, drugs, physical shape, etc. Glaister equation (Rectal temperature) = (98.4° F - rectal temperature)/1.5 = hours elapsed since death. Glaister equation (Rectal temperature) = (98.4° F - rectal temperature)/1.5 = hours elapsed since death. decomposition raises the internal body temperature. decomposition raises the internal body temperature. Can observe incr. of body temp. (closed car in sun, etc.) Can observe incr. of body temp. (closed car in sun, etc.)

CHE Matter; Measurement Temperature Temperature Algor Mortis - drop in body temperature after death. Algor Mortis - drop in body temperature after death. Rigor Mortis - muscular rigidity w/out shortening Rigor Mortis - muscular rigidity w/out shortening Livor Mortis - settling of blood Livor Mortis - settling of blood

CHE Physical Measurements Light Facts: Light Facts: Why are gems colorful and pencils bend? Why are gems colorful and pencils bend? DispersionRefraction

CHE Physical Measurements The index of refraction The index of refraction DispersionRefraction

CHE Physical Measurements The index of refraction (R.I.) of a substance is equal to c (the speed of light in space) divided by the speed of light in that particular substance. The index of refraction (R.I.) of a substance is equal to c (the speed of light in space) divided by the speed of light in that particular substance. SubstanceStateRefractive Index AirGas IceSolid1.31 WaterLiquid1.33 Ethyl AlcoholLiquid1.36 FluoriteSolid1.43 QuartzSolid1.54 SaltSolid1.54 TourmalineSolid1.62 GarnetSolid Cubic ZirconiaSolid DiamondSolid2.41

CHE Physical Measurements Refractive Index - Birefrignence Refractive Index - Birefrignence Gases, liquids, glass and other amorphous are isotropic substances where monochromatic light propagates in all directions with equal velocity. Gases, liquids, glass and other amorphous are isotropic substances where monochromatic light propagates in all directions with equal velocity. Crystals can be anisotropic where the speed with which monochromatic light propagates through those materials varies with crystallographic direction..(multiple RI’s) Crystals can be anisotropic where the speed with which monochromatic light propagates through those materials varies with crystallographic direction..(multiple RI’s) ”Birefringence" refers to the difference between the multiple refractive indices exhibited by an optically anisotropic material ”Birefringence" refers to the difference between the multiple refractive indices exhibited by an optically anisotropic material.

CHE Glass Analysis Glass is found in many types of cases - burglaries and hit- and-runs. Glass is found in many types of cases - burglaries and hit- and-runs. Glass fragments easily embed in shoes and clothing of people involved in the breakage of glass. Glass fragments easily embed in shoes and clothing of people involved in the breakage of glass. Glass can give class characteristics Glass can give class characteristics Can give individual characteristics where a piece of glass that was broken is reconstructed when fractured pieces are fit together. Can give individual characteristics where a piece of glass that was broken is reconstructed when fractured pieces are fit together.

CHE Glass Analysis Mostly Class evidence from: Mostly Class evidence from: Broken Windshield Fracture Match Broken Windshield Fracture Match Stress Marks in Broken Glass Stress Marks in Broken Glass Molotov Cocktail from Fire Molotov Cocktail from Fire Broken Bottles (from inside or outside) Broken Bottles (from inside or outside) Burglery Burglery Vandalism Vandalism Comparison of Glass Fragments Comparison of Glass Fragments

CHE What Is Glass? Glass is made of silicon oxide and metal oxides Glass is made of silicon oxide and metal oxides Sand and metal oxides are melted and then cooled. Sand and metal oxides are melted and then cooled. Yields an amorphous liquid (liquid!). No crystal structure. Yields an amorphous liquid (liquid!). No crystal structure. Glass flows even at room temperature (but very slowly). Glass flows even at room temperature (but very slowly). Hard and Brittle Hard and Brittle

CHE How Is Glass Made? BLOWN OR SPIN GLASS BLOWN OR SPIN GLASS FLOAT GLASS PROCESS FLOAT GLASS PROCESS ROLLED GLASS PROECSS ROLLED GLASS PROECSS

CHE How Is Glass Made? FLOAT GLASS PROCESS - ( 1959, ca. 90% of flat glass) FLOAT GLASS PROCESS - ( 1959, ca. 90% of flat glass) The raw materials (soda lime, silica sand, calcium, oxide, soda and magnesium) are weighted, mixed and melted at 1500° C. The raw materials (soda lime, silica sand, calcium, oxide, soda and magnesium) are weighted, mixed and melted at 1500° C. molten glass flows from the furnace onto a bath of molten tin in a continuous ribbon (glass and the tin do not mix - the contact surface is perfectly flat. molten glass flows from the furnace onto a bath of molten tin in a continuous ribbon (glass and the tin do not mix - the contact surface is perfectly flat. When leaving the bath of molten tin the glass has cooled down sufficiently to pass to an annealing chamber. When leaving the bath of molten tin the glass has cooled down sufficiently to pass to an annealing chamber.

Bell Work for Thursday, October 11 Take out your notebook Take out your notebook You will be getting tests back today You will be getting tests back today We will watch a movie to introduce soil and glass We will watch a movie to introduce soil and glass If time remains after notes, we will start a lab. If not, we will definitely do this tomorrow If time remains after notes, we will start a lab. If not, we will definitely do this tomorrow

Bell Work for Friday, October 12 Pick up the article up front Pick up the article up front Take out your notebook for notes today Take out your notebook for notes today We will finish our movie We will finish our movie After the movie, read the article and you are going to write a summary of the article and then give me your opinion of this article for a grade After the movie, read the article and you are going to write a summary of the article and then give me your opinion of this article for a grade Then few more notes and do a lab Then few more notes and do a lab

What is Glass? “An inorganic product of fusion which has cooled to a rigid condition without crystallizing” “An inorganic product of fusion which has cooled to a rigid condition without crystallizing” Uniform amorphous solid Uniform amorphous solid No specific m.p. No specific m.p. Softens over a temperature Softens over a temperature range range

'Ordinary' sheet glass -made by passing the molten glass through rollers; process gives an almost flat finish but with distortions. -glass is used in glazing greenhouses and garden sheds where the visual distortions do not matter. Float glass (plate) Float glass gets its name from the method of production used to manufacture it. -molten glass is 'floated' onto a bed of molten tin -produces a glass which is flat and distortion free -process imparts a fluorescence to the glass [UV light]

Rolled GlassFloat Glass Float Glass Process

Toughened (Safety glass) -glass is produced by applying a special treatment to ordinary float glass after it has been cut to size and finished. -treatment involves heating the glass so that it begins to soften (about 620 C) and then rapidly cooling it. -produces a glass which, if broken, breaks into small pieces without sharp edges. Laminated glass -glass is made up of a sandwich of two or more sheets of glass (or plastic), bonded together by a flexible, normally transparent material. -if cracked or broken, the flexible material is designed to hold the glass fragments in place.

What’s in Glass? Network Components-Formers: Network Components-Formers: SiO 2, B 2 O 3, P 2 O 5, GeO 2, V 2 O 5, As 2 O 3, Sb 2 O 5 Fluxes–Softeners [lowers melting point]: Fluxes–Softeners [lowers melting point]: Na 2 O, K 2 O, LiO, Al 2 O 3, B 2 O 3, Cs 2 O Stabilizers–Chemical/Corrosion Resistance: Stabilizers–Chemical/Corrosion Resistance: CaO, MgO, Al 2 O 3, PbO, SrO, BaO, ZnO, ZrO

Major Types and Uses Soda lime silicate glass Soda lime silicate glass SiO 2 + Na 2 O / K 2 O + CaO / Al 2 O 3 / MgO Flat glass, container glass, electric light bulbs Flat glass, container glass, electric light bulbs Borosilicate glass Borosilicate glass > 5% B 2 O 3 (replaces Na 2 O) Lab glassware, thermometers, cookware, sealed-beam headlights

Aluminosilicate glass Aluminosilicate glass Higher percentage of aluminum Higher percentage of aluminum higher temperatures than borosilicate higher temperatures than borosilicate Aluminoborosilicate – 50:50 Al/B Aluminoborosilicate – 50:50 Al/B Labware, cookware, and glass fibers Labware, cookware, and glass fibers Lead alkali silicate (leaded glass) Lead alkali silicate (leaded glass) Up to 80% PbO Up to 80% PbO high refractive index high refractive index “Crystal” tableware, “Crystal” tableware,

Different glasses-domestic windows, car headlamps, light bulb glass-are produced differently from different chemistries.

Forensic Individualization of Glass Flat Glass–Soda lime silicate Flat Glass–Soda lime silicate - Rolling or Floating Tempered: Rapid Cooling Tempered: Rapid Cooling Adds Strength Adds Strength Dices when broken Dices when broken Automotive windows & security windows Automotive windows & security windows Float Glass floresces when excited at 254 nm. Float Glass floresces when excited at 254 nm.

Coated: Surface modification Coated: Surface modification Mirrors Mirrors Laminated: Sandwiched around plastic Laminated: Sandwiched around plastic Automotive windshields Automotive windshields Headlights: often borosilicate Headlights: often borosilicate Light bulbs: soda lime glass Light bulbs: soda lime glass Heat absorbing/ UV filtering Heat absorbing/ UV filtering tinting tinting Eyeglasses: prescription lenses/photosensitive Eyeglasses: prescription lenses/photosensitive

Container Glass Container Glass Lower magnesium, higher sodium Lower magnesium, higher sodium Clear vs. greenish (window) Clear vs. greenish (window) Glass Fibers Glass Fibers Fiberglass insulation Fiberglass insulation Alumino-borosilicate Alumino-borosilicate Binder (red or yellow) to hold fibers in bundles Binder (red or yellow) to hold fibers in bundles

Forensic Analysis of Glass Fundamental Question: Is it Glass? Isotropic vs. Anisotropic Isotropic vs. Anisotropic Glass: Isotropic Glass: Isotropic dark when rotated under crossed polarizers dark when rotated under crossed polarizers Crystalline solids and plastics: Anisotropic Crystalline solids and plastics: Anisotropic Change retardation when rotated under crossed polarizers Change retardation when rotated under crossed polarizers Hardness Hardness Solubility Solubility

Comparison of Physical Characteristics Color Color Flatness Flatness Thickness Thickness Fluorescence–Float Glass Fluorescence–Float Glass 254 nm 254 nm

Physical Properties Density Density Sink-Float Method Sink-Float Method CHBr 3, C 2 H 2 Br 4, Sodium Polytungstate CHBr 3, C 2 H 2 Br 4, Sodium Polytungstate Density Range: Density Range: g/cm g/cm 3

When 2 substances have different RI, light passing through them produces a Becke Line A Becke line is a band or rim of light visible along a grain/crystal boundary in plane-polarized light.

Glass analysis is often performed using our old friend the PLM -the goal of glass analysis by PLM is to individualize an evidence glass fragment to an exemplar from a crime scene [primary or secondary]

Populations of Glass RIs

GRIM II System -automated system for matching glass RI -uses a step-heating stage and a RI liquid that varies with temperature

GRIM II identifies the RI match by monitoring a video image of the glass fragment in the liquid -as it is heated/cooled the contrast is measured until a minimum is reached-the match point

Chemical Composition – Chemical Composition – Inductively Coupled Plasma (ICP) Inductively Coupled Plasma (ICP) SEM/EDS SEM/EDS Neutron Activation Analysis Neutron Activation Analysis X-Ray Fluorescence X-Ray Fluorescence

How does Glass break? Forensic Fracture Analysis

Radial Begin at a point and radiate outward from point of impact -initial crack is on the side opposite the applied force

Concentric Motion of the projectile through the glass puts tension on the front surface of the glass, causing concentric fractures. -high-speed projectile [a rock] penetrates the glass, it leaves an exit hole larger than it's entrance hole. -helps to determine the direction on impact.

A determination of the direction of force in breaking a window pane: -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 parts of the rib marks.

Bullets and Glass It’s possible to determine the bullet's direction by noting the side of the cone- shaped hole left by the bullet. -small opening is on the entrance side

Counting Bullet Holes Determination of the sequence of bullet holes can be made by noting the radial fractures. Radial fractures caused by the passage of a bullet stop at pre- existing fracture.

CLASS AND INDIVIDUAL CHARACTERISTIC EVIDENCE Class: a group of objects or persons with characteristic physical evidence common to it Class: a group of objects or persons with characteristic physical evidence common to it Examples include soil and hair Examples include soil and hair Individual characteristics can be identified as having originated with a particular person or source Individual characteristics can be identified as having originated with a particular person or source Establishes individuality Establishes individuality Examples include fingerprints and footprints Examples include fingerprints and footprints

PRESERVING FOOTWEAR AND IMPRESSIONS Footwear prints and impressions should be photographed: Footwear prints and impressions should be photographed: As part of the general scene As part of the general scene Also photograph with a scale Also photograph with a scale Dental Stone is used in casting impressions Dental Stone is used in casting impressions We will use Plaster of Paris We will use Plaster of Paris

Warm Up Which glass is common and inexpensive? Which glass is common and inexpensive? Which glass is strengthen due to rapid heating and cooling? Which glass is strengthen due to rapid heating and cooling? Which glass contains lead oxide? Which glass contains lead oxide? Which glass bonded together with a plastic film? Which glass bonded together with a plastic film? **Turn in Ch. 12, 14, 15 Vocab. To back table

When you are finished with the test.. Make sure your name is at the top and turn into bin Make sure your name is at the top and turn into bin Pick up your notebook from back lab station Pick up your notebook from back lab station Work on Vocabulary for Ch. 3 and 4 Work on Vocabulary for Ch. 3 and 4 Start working on notes if you finish vocabulary early Start working on notes if you finish vocabulary early

FOOTWEAR IMPRESSIONS Photographs of footwear impressions at a crime scene Photographs of footwear impressions at a crime scene In the first photo only the impressions are shown In the first photo only the impressions are shown In a subsequent photo a ruler will be added to show sizes In a subsequent photo a ruler will be added to show sizes Later casts will be made of the impressions Later casts will be made of the impressions

Why are footprints important Footprints and tireprints Footprints and tireprints When someone walks or runs, or drives a vehicle, over soil, impressions are left in the ground. A frame is built around the print or track, a suitable casting material is poured in and allowed to dry, and then the cast removed and photographed. As shoes and tires are used, individual characteristics such as nicks, cuts, and wear patterns develop. These characteristics may show up in prints and impressions and can be compared with a suspect's shoes or tires. When someone walks or runs, or drives a vehicle, over soil, impressions are left in the ground. A frame is built around the print or track, a suitable casting material is poured in and allowed to dry, and then the cast removed and photographed. As shoes and tires are used, individual characteristics such as nicks, cuts, and wear patterns develop. These characteristics may show up in prints and impressions and can be compared with a suspect's shoes or tires. Footprints Footprints Through the skilful combination of tracking and footwear impressions, it is often possible to recreate the events leading up to, those occurring during, and those occurring after the crime. Through the skilful combination of tracking and footwear impressions, it is often possible to recreate the events leading up to, those occurring during, and those occurring after the crime.

Collection of evidence Photography: Black and white film is normally used, unless the impression is in blood, and oblique light is shone onto the footprint. It is usual to take a series of photographs, each time varying the position of the light source, and a scale should be added to the scene. If the surface is light, the print may be highlighted using aerosol paint. Photography: Black and white film is normally used, unless the impression is in blood, and oblique light is shone onto the footprint. It is usual to take a series of photographs, each time varying the position of the light source, and a scale should be added to the scene. If the surface is light, the print may be highlighted using aerosol paint.

How to make a casting At the scene of the crime, a footprint is observed in the soil. Your task is to make a cast of the footprint. At the scene of the crime, a footprint is observed in the soil. Your task is to make a cast of the footprint. 1 Make a dam around the impression of the footprint to hold the plaster. If the soil is of a loose sandy type, use shellac or hair spray to firm the soil before pouring in the cast. Be careful in directing the spray of the "fixer" so that it does not blow away the impression. 1 Make a dam around the impression of the footprint to hold the plaster. If the soil is of a loose sandy type, use shellac or hair spray to firm the soil before pouring in the cast. Be careful in directing the spray of the "fixer" so that it does not blow away the impression. 2 Mix the casting medium according to the instructions provided (Dental Stone if available; Plaster of Paris, if not). The ideal mixture should be pancake batter consistency. 2 Mix the casting medium according to the instructions provided (Dental Stone if available; Plaster of Paris, if not). The ideal mixture should be pancake batter consistency.

Casting Continued 3 Pour the mixture carefully down a spatula to fill the entire impression. 3 Pour the mixture carefully down a spatula to fill the entire impression. 4 Allow the cast to set for at least an hour before removing it. 4 Allow the cast to set for at least an hour before removing it. 5 Comment on the characteristics of the shoe from which the impression must have been made. The impression can be compared with a shoe of the suspect, if one has been apprehended. 5 Comment on the characteristics of the shoe from which the impression must have been made. The impression can be compared with a shoe of the suspect, if one has been apprehended.

What about flat footprints? When footprints appear on a porous material like paper or cardboard, application of a low adhesive gelatine layer lifts the prints, which can be taken away for photography and closer analysis. Sometimes, the application of fingerprint powders or electrostatic powders, or use of appropriate lighting reveals latent prints, and black, white or transparent lifters are used.

Footprint Analysis: What can they tell us? Footprint impressions from casts and/or by photography will give investigators information about: Footprint impressions from casts and/or by photography will give investigators information about: · The number of criminals. · The number of criminals. · Points of entry and exit. · Points of entry and exit. · Positions of suspect(s), victim(s) and witness(es). · Positions of suspect(s), victim(s) and witness(es). · Direction(s) of movement/travel and pathway(s) through the crime scene. · Direction(s) of movement/travel and pathway(s) through the crime scene. · Time period, from short-lived impressions in frost, snow, dew. · Time period, from short-lived impressions in frost, snow, dew.

What else can they tell us? · Sequence and manner (walking, running, limping, staggering) in which the impressions were created. · Sequence and manner (walking, running, limping, staggering) in which the impressions were created. · Links between crime scenes, e.g. the same criminals committing several crimes in one evening. · Links between crime scenes, e.g. the same criminals committing several crimes in one evening. · The type, size and areas of specific wear on the shoes. · The type, size and areas of specific wear on the shoes. Certain seasons or weather conditions lend themselves to the creation of footprint impressions than others. Soil trapped in soles can also give useful leads, such as soil pH, specific minerals or heavy metals in the soil, the presence of seeds or pollen grains. Certain seasons or weather conditions lend themselves to the creation of footprint impressions than others. Soil trapped in soles can also give useful leads, such as soil pH, specific minerals or heavy metals in the soil, the presence of seeds or pollen grains.