Forensic Science Chapter 10 & 11 Test Review, trace evidence - glass, Evidence Handling and Trace Evidence

ASTM definition of glass

"an inorganic product of fusion which has cooled to a rigid condition without crystallizing"

ISOTROPY & how a POLARISING microscope can be used to discriminate between glass & other translucent material confused with glass

# Before testing glass particles - must be confirmed they are glass # Tested by measuring Hardness, Structure & Behaviour when exposed to POLARISED light GLASS # If a thin layer of glass is examined under cross polars - it will disappear as its ISOTROPIC - behaves the same at any orientation of a polarizer # Crossing the polar - glass as an ISOTROPIC material will appear DARK & stay dark on rotation # Only 1 Refractive Index for given temp & wavelength of light OTHER MATERIALS (crystalline solids/plastics) # Will show diff colours & brightness when exposed to POLARISED light # Translucent substances are ANISOTROPIC - they're doubly refracting # Upon crossing the polars - other (ANISOTROPIC) materials - will allow some LIGHT to pass/will be generally light, execpt in spec orientations (90 degrees)

Striations

# Coarse marks PARALLEL to one another # Seen with unaided eyes # Lie PARALLEL to direction of fracture propagation # Sometimes poss to show physical match of striations between 2 pieces of glass that were once joined

Conchoidal Marks

# Curved (J-shaped) shell like marks # In RADIAL FRACTURE - they are at rigt angle to side OPP to where impact occurred # In CONCENTRIC FRACTURE - they are at right angle to same side where impact occurred

Non-Convertible Paints

# No chemical reaction takes place # Film dries due to solvent evap # Emulsion paint a non-onvertible paint (contains non-convertible acrylic polymer as binder)

Convertible Paints

# Paints undergo OXIDATION causing the film to set slowly & dry the product # Once paint undergo chem reaction no longer soluble in orig liquid paint used # Drying of paint catalyzed by driers (chemical analysts)

Major Components use to make flat glass

# SAND (Silica Oxide) # SODA (Sodium Oxide) # LIME (Calcium Oxide)

Toughened Glass

# Stronger than window glass # Made stronger by introducing STRESS MARKS through rapid heating & cooling of glass surface # When breaks doesnt shatte, "dices" into small squares # Used in side/rear windows of automobiles

Annealing

# The process whereby glass is HEAT-TREATED to remove the stresses in it # Heated to high temp for prolonged period of time (550 degrees for 1-24 hrs) then slowly cooled to room temp # Toughened glass shows increase of 140x10^-5 in RI

Is the fragment glass?

-Scratch Test- application of pressure with a needle causes deformation of a particle, -Then it is plastic not glass. -Organic Solvents- some plastics are soluble in organic solvents. PLM-Glass is an amorphous solid and is therefore isotropic

Handling of crime scene glass samples

-Identify and photograph any glass samples before moving them. -Collect the largest fragments that can be reasonably collected. -Identify the outside and inside surface of any glass. -If multiple panes are involved, make a diagram. -Note trace evidence such as skin, hair, blood, or fibers. -Package all materials collected to maintain the chain of custody.

Paint examination

1. Paint examination - optical microscopy 6 or more matching layers at this stage, no further work, association proved 2. Paint examination - infrared microscopy Provides information about different binder types and fillers/pigments 3. Paint examination - UV-Vis Objective colour comparison of paint 4. Paint examination - SEM/EDX Elemental and inorganic analysis of paints and coatings

Questions to ask of glass evidence

1.Is the fragment glass? 2.What compositional class and product type is it? 3.Do the two fragments of glass have the same source 4.What is the significance of a glass analysis match?

A minimum collection of ____ full-length pubic hairs is recommended to cover the range of characteristics present in this region of the body.

24

B) decrease

5. As the temperature of a gas increases, the density of the gas will __________. A) increase B) decrease C) remain constant

A minimum collection of ____ full-length hairs normally ensures a representative sampling of head hair.

50

D) atmospheric pressure

A barometer is a device for measuring ________. A) gas pressure in a container B) blood pressure C) vapor pressure D) atmospheric pressure E) gas pressure in the lung

A control sample which is known to be free of the item or substance being tested is referred to as:

A blank sample

A sample which is known to be free of the item or substance being tested is referred to as

A control sample

What is trace evidence?

Anything that can occur by contact between two items

In what types of cases might glass evidence be important?

B&E - glass fragments on suspect's clothes, Hit and Run - glass fragments at scene of crime linked to the headlight of the suspect vehicle

If the refractive index of a liquid medium is different than the refractive index of the piece of glass a halo like ring appears around the edge of the glass. This halo like affect is called a

Becke line

The bright halo that appears near the border of a glass particle that is immersed in a liquid of a different refractive index is called the:

Becke line

Glass Fractures

Being an amorphous solid, will not break into regular pieces with straight-line fractures

What are the two most important components of dried paint from the criminalist's point of view?

Binder and the pigment

Describe the basic composition of paint. What component of paint evaporates after paint is applied to a surface?

Binder, pigments, and other additives, dissolved or dispersed in a suitable solvent. After the paint has been applied to a surface, the solvent evaporates.

Hair can best be characterized as originating from an animal be examining.....

Both the medulla and cuticle

Examination of Documents

Comparison of unknown documents with known documents Connection between a crime and an individual, or exclusion of an individual Results may provide invaluable evidence to the court

A substratum specimen serves what purpose in the physical evidence examination process?

Comparison sample A substratum is a comparison specimen A sample of the material or surface on which biological evidence is deposited

Establishing the exact whereabouts of an item of evidence and under whose control it was from the time of its collection to its admissibility as evidence in court, is known as maintaining the:

Chain of custody

What type of fracture forms on the same side as the impact?

Concentric

Glass Fibers

Continuous filament, fiber glass, and non-continuous filament, fiberglass wool (insulation)

ICP-AES Advantages:

Determine wide range of elements, limited number of interferences, excellent detection limits, ease of automation

ICP-AES Disadvantages:

Dissolution of glass fragments and the associated problems

How is the hair cuticle used to identify different animal species?

Distinctive scale pattern

SEM/EDX Advantages:

Distinguishes between glass samples due to the elements present and there relative intensities for the amount of the element. Non-destructive

Stabilizers

Divalent cations-Calcium, magnesium, to provide chemical resistance and keep the glass structure intact

Which of the following statements is not true? A questioned sample is sometimes referred to as a disputed sample Class characteristics enable an object to be placed into a particular category Individual characteristics are unique to a particular object A class characteristic is one that enables an object to be uniquely identified

FALSE: A class characteristic is one that enables an object to be uniquely identified Rather, class characteristics are: Measurable features of an item that indicate a restricted group source based on design factors determined prior to manufacture May be shown to be like or consistent with a questioned source, although not uniquely identifiable with that source

Fingerprinting

Fingerprinting after Document Examination

Transfer and Persistence

Fragments are ejected from the glass both with and against the direction of force. Number of fragments transferred and retained depends on: Type and thickness of glass, Number and force of blows to the glass, Method of striking the glass, Distance between the glass and the recipient, Type of garment worn by the recipient

Which of the following statements is FALSE? Hair continues to grow after you die Identical twins have identical DNA Identical twins do not have identical fingerprints Teeth are a good source of DNA for forensic analysis

Hair does not continue to grow after a person dies. Instead, the skin tends to retract which makes the hair protrude more

What types of hair specimens are potentially the richest source of nuclear DNA and why?

Hair forcibly removed with follicular tag.

High Velocity Impact Fractures

High velocity projectiles will produce coning or a cratering effect, with the opening being larger on the exit side. Shape of the cone produced depends on the angle of impact of the projectile

Alumino-silicate Glass

Higher % of aluminum added. Withstands higher temps than borosilicate, resistant to alkalis. Common in lab-ware, glass fibers, and stovetop cookware.

In what types of criminal cases is paint evidence most frequently encountered?

Hit and Run

The examination of physical evidence by a forensic scientist is usually undertaken for:

Identification and comparison purposes

Heat-absorbing Glass

Oxides added to molten glass to absorb certain wavelengths and filter out heat and UV rays- tinted and lacks transparency

What is the follicular tag and why is it important to forensic scientists studying hair?

Piece of tissue surrounding hair shaft near root which contains richest source of DNA

The cortex of hair derives its major forensic importance from the fact that it contains....

Pigments

One of the fundamental tenets underlying forensic science is that when two objects come into contact with each other, material is swapped between them. What name, honoring the Frenchman who developed it, is given to this philosophy?

Locard's Exchange Principle Edmond Locard (1877-1966) set up the first laboratory to apply current scientific methods to criminal investigations in Lyons during 1910. At that time, his equipment was limited to a microscope and a simple spectrometer. His idea that a perpetrator could be tied to the crime scene through cross-transfer of often microscopic evidence (e.g. threads from clothes) during contact soon led to great international interest in the fledgling forensic sciences. One famous case involved identifying suspects in a lucrative coin counterfeiting ring through minute metal particles in their clothing. Over the next two decades, police laboratories were established in many cities throughout Europe. In 1932, FBI Director, J. Edgar Hoover ordered the establishment of a national forensic laboratory to support police activities across the USA. However, credit for the theory underpinning forensic science should at least be shared with the Austrian judge and prosecutor, Hans Gross (1847-1915) who in 1893 wrote the first treatise outlining how the scientific method might be applied to criminal cases

When two objects touch, there is a transfer of material from one to the other. This trace evidence is the basis of forensic science. What is the idea known as?

Locard's principle Dr Edmond Locard opened the world's first police crime laboratory in 1910 in Lyon, France. Locard was a student of Bertillon, also a pioneer of forensic science.

What are naturally occurring crystals commonly found in soils?

Minerals

ICP-MS Disadvantages:

More difficult to run and prepare samples (large contamination issues), and analytical precision is not as good as ICP-AES

Borosilicate Glass

More than 5% boric acid added, Replacement of Sodium with Boron creates a lower thermal expansion and greater resistance to acid corrosion. Common in lab-ware, thermometers, household cookware, and sealed-beam headlights.

SEM/EDX Disadvantages:

Quantitative determination is difficult due to surface irregularity. Detection limit is poor, 0.1% range

Soda-Lime-Silicate Glass

Quartz + Na & K + Ca, Mg & Al. Common in flat glass, bottles/containers & light bulbs

Direction of Force: 4R rule

Ridges on Radial cracks are at Right angles to the Rear (side opposite the impact) -Can not be determined with tempered glass or laminated glass

Glass Definition

Rigid, Hard, Brittle (breaks easily), -Transparent to Translucent, Amorphous substance (non-crystalline)

Elemental Composition Determination:

SEM/EDXA, XRF, FAAS, ICP-AES, ICP-MS

What are the three parts of the hair? Define each.

Shaft - part of the hair that sticks out of the skin Root - lies below the epidermis Follicle - structure from which the hair grows

Formers

Silicon Oxide (SiO2) -quartz sand forms the loose framework of the glass structure, solidifies without crystallizing

Materials used to create (soda-lime) glass:

Silicon dioxide (SiO2) Sodium oxide (Na20) Calcium oxide (CaO) ( most common glass)

An example of a natural fiber would be: Silk Bran Nylon Rayon Feathers

Silk

The speed of light passing through air is slightly

Slower than the speed of light passing through a vacuum because air is slightly denser than a vacuum

XRF Disadvantages:

Small irregularly shaped particle quantitative problems are more pronounced than SEM/EDX

Bottles/Containers

Soda-lime-silicate glass with lower amounts of magnesium and more amounts of calcium

When light travels through any medium other than a vacuum, the particles in that medium slow the light down as the density of the medium increases the

Speed of light passing through that material decreases

If the reflective index of a several different liquids are known the

Submersion method can be used to estimate the refractive index of the glass

Uncontaminated surface material close to an area where physical evidence has been deposited is a:

Substrate control

Glass which is strengthened by introducing stress through rapid heating and cooling of it's surface.

Tempered Glass

Glass that is made stronger than ordinary window glass by introducing stress through rapid heating and cooling of the glass surface is called:

Tempered glass

A bright halo that is observed near the border of a particle immersed in a liquid of a different refractive index is known as:

The Becke Line

Why radial and concentric fractures form

Impacted glass is compressed on the side it is hit. It will stretch on the opposite side of the glass, and the tension there will radiate breaks in the glass outward from the point of impact. Then fractures form in the shape of concentric circles on the same side of the impact.

C) V decreases, temperature

In Charles' law, the ________ when the ________ decreases. A) V decreases, pressure B) T increases, pressure C) V decreases, temperature D) V increases, quantity of gas E) P increases, temperature

Why are most hair specimens collected at crime scenes not good sources?

Most in telogen stage so they contain the least amount of DNA

Silica Glass

Just molten quartz with no additives. Low thermal expansion, high service temp, transparency to wide range of wavelengths, superior chemical and electrical resistance. High cost.

As a bullet passes through glass, it pushes some glass ahead of it, causing a cone shaped piece of glass to exit along with the bullet. The cone of glass makes the exit hole:

Larger than the entrance hole of the bullet

Headlights

Lenses and reflectors are made by stamping gobs of glass from a continuous flow. Modern lenses are normally made from plastic

A piece of glass is immersed in a liquid and proceeds to float on the surface. This shows that the density of glass is______ The density of the liquid

Less than

Which of the following evidence collection procedures is considered to be the method of "last resort"?

Vacuuming

Which of the following evidence collection procedures is considered to be the method of 'last resort' Tape lifting scraping Vacuuming Cutting swabbing

Vacuuming

Methods of collection

Vary depending on the type of material •Hand picking •Tapelifting •Brushing/shaking •Vacuuming •Swabbing •Bagging (headspace collection)

Why does the composition of glass vary?

Varying raw materials, Varying techniques of mixing of raw materials, Breakdown of furnace over time

Hemp fibers are classified as:

Vegetable fibres

Who may you get hair samples from?

Victims, possible suspects, and others who may have deposited hair at the scene

Obsidian refers to

Volcanic glass

Before fingerprints, what did people do for identification?

The correct answer was measured people's bodies This system of measuring bodies was called bertillonage. It was named after its creator Alphonse Bertillon. The system took eleven measurements, height sitting and standing, the length of the left arm, etc. As fingerprints became popular Bertillon's system fell out of use.

The portion of the hair containing scales is...

The cuticle

What is the hair cuticle?

The cuticle is the outermost layer of hair which is covered with scales.

The submersion method involves placing the glass fragment into different liquids of knowing the fact of indexes. If a piece of glass and liquid have the same refractive index in the glass fragments will seem to

To disappear when placed in the liquid

Each type of glass has a density that is specific to that glass. One method of matching glass fragments is by a density comparison

True

Fine glassware and decorative art glass, called crystal or leaded glass, contain lead oxide rather than calcium oxide

True

Glass fragment comparison is the comparison of two or more glass fragments in an attempt to determine if they originated form different sources.

True

Glass is a hard, amorphous material made by melting sand, lime, and also called calcium oxide, and sodium oxide at high temperatures

True

If bloodstained materials are stored in airtight containers, such as pill bottles, vials or other similar containers, the accumulation of moisture may encourage the growth of mold, which can destroy the evidential value of blood

True

Much of hair's ability to resist decomposition is attributed to its cortex.

True

One of the tasks of the forensic scientist when examining physical evidence is to find as many characteristics as possible to compare one substance with another.

True

Shed scalp hair samples generally have little to no root sheath material.

True

T/F: The scales of most animal hairs can be described as looking like shingles on a roof

True

T/F: Two hairs from the same head may not have the same morphological characteristics.

True

The normal variation within an individual's handwriting is much less than the variation between handwriting from two different individuals.

True

The physical properties of density and refractive index are used most successfully for characterizing glass particles.

True

True / False: Value of soil as evidence resides with its prevalence at crime scenes and its transferability between the scene and the criminal

True

True or false: Scientific crime scene investigation is based on the Locard transfer theory of physical evidence, scientific testing techniques, and basic logical reasoning

True

When soil is found on a suspect's garments or shoes, the investigator should remove the soil by gently scraping the soil into an airtight container for later analysis.

True

The examination of evidence requires comparison with a "substrate control" to ensure the evidentiary value of the crime-scene evidence.

True A substrate control is uncontaminated surface material located close to an area where physical evidence has been deposited

Lead-Alkali-Silicate Glass (Leaded Glass)

Up to 80% PbO. Lower softening temp, higher refractive index and dispersion and filters out certain wavelengths of light. Common in "crystal" tableware, costume jewelry, chandeliers, neon sign tubing and video tubes

Density

The formula for calculating density is: D = m / V m = mass, measured by a balance beam device V = volume, place the glass fragment into a beaker filled with water and measure the overflow D = density, divide the mass (in grams) by the volume (in milliliters)

C) PV = nRT

The mathematical expression of the ideal gas law is ________. A) P₁/V₁ = P₂/V₂ B) PT = P₁ + P₂ + P₃ C) PV = nRT D) P₁V₁ = P₂V₂ E) P₁/T₁ = P₂/T₂

What is the hair medulla?

The medulla is the hair core that is not always present.

Because glass is a solid with random arrangement of motionless atoms, it is called:

amorphous

The weight 264.45 grams can be correctly expressed as: a. 26,445 decigrams. b. 0.26445 kilograms. c. 26.445 centigrams. d. None of the above

b. 0.26445 kilograms

The basic metric unit for volume is the a. Centimeter. b. Liter. c. Milliliter. d. Gram.

b. Liter

_____ is the visual effect caused by an object's absorption of certain portions of the visible light spectrum and transmission or reflection of others. a. Dispersion b. Color c. Density d. Refractive Index

b. color

If an object is immersed in a liquid of greater density, it will: a. Be suspended in the liquid b. Float c. Sink d. Be suspended for a known period of time before sinking

b. float

The density of water at 60°F is _____ the density of water at 28°F. a. Less than b. Greater than c. The same as d. None of the above

b. greater than

A piece of glass is immersed in a liquid. It proceeds to float on the liquid's surface. This shows that the density of the glass is _____ the density of the liquid. a. More than b. Less than c. Equal to d. Not comparable

b. less than

Which physical state has volume but no specific shape? a. Gas b. Liquid c. Solid d. No such state exists

b. liquid

Stress marks on the edge of a radial crack near the point of impact are: a. Perpendicular to the side on which the force was applied. b. Parallel to the side on which the force was applied. c. Parallel to the side opposite the side on which the force was applied. d. Perpendicular to the side of the glass facing outdoors.

b. parallel to the side on which the force was applied

The heat intensity (hotness) of water at 100°C is _____ the heat intensity of water at 212°F. a. Greater than b. The same as c. Less than d. None of the above

b. the same as

Cullet glass

broken recycled glass, acts as a flux for the more difficult-to-melt quartz. Lowers production cost, extends life of furnace.

Which of the following is an element? a. Wood b. Water c. Aluminum d. Air

c. Aluminum

The freezing point of water in Fahrenheit is _____ the freezing point of water. a. Less than b. The same as c. Greater than d. None of the above

c. Greater than

The use of the Celsius temperature scale by scientists is _____ their use of the Fahrenheit temperature scale. a. Greater than b. The same as c. Less than d. None of the above

c. but should be a

The density of liquids is ________ the density of gases. a. Less than b. The same as c. Greater than d. None of the above

c. greater than

Pyrex glass: a. Is put through an annealing process. b. Has been tempered. c. Is made with the addition of boron oxide. d. Is laminated.

c. is made with the addition of boron oxide

The attraction between the molecules of a gas is _____ the attraction between the molecules of a liquid. a. The same as b. Greater than c. Less than d. Unrelated to

c. less than

The fracture pattern of glass usually has: a. Radial lines. b. Concentric lines. c. Radial and concentric lines. d. Directional lines.

c. radial and concentric lines

If glass cannot be physically pieced together then the control and question glass are best compared as to their: a. Color and density. b. Weight and density. c. Refractive index and density. d. Refractive index and weight.

c. refractive index and density

The two most important physical properties of glass for forensic comparisons are: a. Color and density b. Weight and density c. Refractive index and density d. Refractive index and weight

c. refractive index and density

What is the main ingredient in ordinary glass? a. Lime (CaO) b. Soda (NaCO) c. Sand d. Metal oxides

c. sand

Tempered glass is used in: a. Windshields in autos manufactured in the United States. b. Crystal stemware. c. The side and rear windows of autos manufactured in the United States. d. Both b and c

c. the side and rear windows of autos manufactured in the US

Which color of the visible spectrum has the highest frequency and the shortest wavelength? a. Red b. Green c. Violet d. Yellow

c. violet

Which is NOT an intensive property of matter? a. Density b. Refractive index c. Weight d. Temperature

c. weight

Which of the following statements is true? The risk of contamination of evidence is controlled and/or minimised by:

chain of custody labels opening each package in an area other than where it was originally sealed storing packages in a dedicated secure area minimising the number of people handling the evidence

fluxes

change the temperature at which the formers melt during the manufacturing of glass

All glass at the crime scene should be

collected

carbonate sands

composed of various forms of calcium carbonate

Eight inches is approximately _____ centimeters. a. 17 b. 10 c. 8 d. 20

d. 20

The refractive index of a substance varies with: a. Its temperature. b. The wavelength of the light passing through it. c. The color of the light passing through it. d. All of the above

d. All of the above

Which of the following is false? a. The basic building blocks of all substances are elements. b. Elements are composed of atoms. c. Two or more elements combine to form compounds. d. At present, 96 compounds have been identified.

d. At present, 96 compounds have been identified

The periodic table is a: a. Forensic text table of contents. b. Forensic newsletter issued periodically. c. Special laboratory surface for multiphase experiments. d. Chart listing all the known elements by name and symbol.

d. Chart listing all the known elements by name and symbol

To explain the events that occur after radiation is absorbed by a substance, light must be characterized as: a. A wave of constant frequency. b. A wave of variable frequency. c. A wave consisting of non-discrete particles. d. A stream of discrete particles.

d. a stream of discrete particles

The smallest particle of an element that can exist and still retain its identity as that element is the: a. Compound. b. Element. c. Photon. d. Atom.

d. atom

Crystalline solids, with the exception of _____ crystals, exhibit _____, or the property of refracting a beam of light into two different ray components. a. Amorphous, refraction b. Calcite, refractive index c. Glass, optical properties d. Cubic, double refraction

d. cubic, double refraction

The process of a glass prism separating sunlight into component colors is called: a. Refraction b. Birefringence c. Sublimation d. Dispersion

d. dispersion

A(n) _____ property describes the behavior of a substance without reference to any other substance while a(n) _____ property describes the behavior of a substance when it reacts or combines with another substance. a. Optical; birefringent b. Physical; biological c. Chemical; biological d. Physical; chemical

d. physical; chemical

The photons of which source have the LEAST amount of energy? a. Microwaves b. Gamma rays c. Infrared rays d. Radio waves

d. radio waves

Sublimation is defined as a change of state from: a. Gas to liquid. b. Liquid to solid. c. Solid to liquid. d. Solid to gas.

d. solid to gas

Which of the following has higher frequencies and higher energy values in the electromagnetic spectrum? a. Visible light b. Radio waves c. Ultraviolet radiation d. X-rays

d. x-rays

A physical property of matter that is equivalent to the mass per unit volume of a substance.

density

Currently the best way to characterize glass particles is through

density and refractive index

chemical properties

describes the behavior of a substance when it reacts or combines with another substance; wood burns, heroin with Marquis reagent turns purple

physical properties

describes the behavior of a substance without having to alter the substance's composition through a chemical reaction; weight, volume, color, boiling and melting point

Fracture patterns provide clues about the...

direction, rate, and sequence of the impacts

Panama City, FL

Which sand sample matched the sand at the crime scene?

Fibre Examinations

White cotton fibres and blue cotton denim fibres - low evidentiary value If there has been any legitimate contact b/n the suspect and the victim - no evidential value

How should soil evidence adhering to shoes and clothing be collected and packaged?

Wrapped individually in paper with the soil intact. Clothing should be carefully and individually wrapped in paper bags.

Becke Line

a bright halo around a particle when it is immersed in a liquid with a different RI. By increasing the working distance on a microscope, the Becke Line moves into the medium with the higher R.I.. When the Becke Line "disappears", the refractive index has been reached.

Becke line

a bright halo that is observed near the border of a particle that is immersed in a liquid

mass

a constant property of matter that reflects the amount of material present

flotation

a control glass particle is immersed in a liquid mixture of bromoform and bromobenzene; the composition of the liquid is carefully adjusted by adding small amounts of the two liquids until the glass chip remains suspended in the liquid; at this point, the control glass and liquid have the same density

radial fracture

a crack in a glass that extends outward like the spoke of a wheel from the point at which the glass was struck

concentric fracture

a crack in a glass that forms a rough circle around the point of impact

Concentric fracture

a crack in the glass from a rough circle around the point of impact

Radial fracture

a crack in the glass that extends outward like the spoke of a wheel

birefringence

a difference in the two indices of refraction exhibited by most crystalline materials

fracture termination

a fracture always terminates at an existing line of fracture

Becke Line

a halo-like effect appearing at the edges of a glass fragment when the reflective index of the glass and liquid are different

Glass

a hard, amophus, transparent material made by heating a mixture of sand and other activities

glass

a hard, brittle, amorphous substance composed of silicon oxides mixed with various metal oxides; main ingredient is sand

refractive index

a tool used to study how light bends as it passes from one substance to another

The physical state that has both shape and volume is a: a. Solid. b. Liquid. c. Gas. d. Vapor.

a. Solid

The effect of gravity on the weight of an object is ________ the effect of gravity on the mass of the same object. a. The same as b. Less than c. Greater than d. None of the above

a. but should be c

Flotation is a method used by scientists to determine the _____ of a particle of glass. a. Density b. Refractive index c. Mass d. Weight

a. density

The change in refractive index for tempered glass upon annealing is _____ when compared to nontempered glass. a. Greater b. The same as c. Less than d. None of the above

a. greater

When a bullet penetrates a panel of glass, it leaves a crater-shaped hole that: a. Is wider on the exit side. b. Is wider on the entrance side. c. Forms randomly and hence the direction of impact cannot be determined by its appearance. d. a or c

a. is wider on the exit side

Which is a true statement about the fracturing of glass? a. Radial cracks appear first, starting on the side opposite the destructive force. b. Radial cracks form afterward, starting on the same side as the destructive force. c. Concentric fractures form first, starting on the side opposite the destructive force. d. Concentric fractures form first, on the same side as the destructive force.

a. radial cracks appear first, starting on the side opposite the destructive force

A hot-stage microscope or the GRIM 3 is used to determine the _____ of glass fragments. a. Refractive index b. Relative density c. Metallic oxide content d. Temperature

a. refractive index

One milliliter of a liquid is _____ 1cc of the same liquid. a. The same as b. Greater than c. Less than d. None of the above

a. the same as

The refractive index of a medium is determined by the ratio of: a. Velocity of light in a vacuum to velocity of light in a medium. b. Density of light in the medium to density of light in a vacuum. c. Frequency of light in a vacuum to frequency of light in a medium. d. Velocity of light in a vacuum to frequency of light in a medium.

a. velocity of light in a vacuum to velocity of light in a medium

sodium oxide

added to reduce the melting point

Corroborative evidence is:

evidence that supports other evidence

Aluminum

feldspar and kaolin. Inhibits devitrification and improves chemical durabililty

One of the most common types of paint examined in the crime laboratory involves:

finishes emanating from automobiles

ocean floor sands

formed from volcanic material, usually basalt

continental sands

formed from weathered continental rock, usually granite

tufa sands

formed when calcium ions from underground springs precipitate with carbonate ions in salt water in a salt lake

Laminated glass

found in car windshields has a layer of plastic between two pieces of ordinary window glass.

Quartz sand (SiO2)

found in many areas, small number of sources with the purity needed for glass making. Contaminants-Iron, ilmenite, corundum, chronite.

Celsius Scale

freezing point is 0 and boiling point is 100

Fahrenheit Scale

freezing point is 32 and boiling point is 212

Leaded glass

glass containing lead oxide

Inductively coupled plasma emission spectrometry has been successfully applied in the identification and characterization of:

glass fragments and mutilated bullets

immersion method

glass particles are immersed in a liquid medium whose refractive index is varied until it is equal to that of the glass particle

GRIM 2

glass refractive index measurement; a automated approach for measuring the refractive index of glass fragments

Tempered glass

glass which is strengthened by introducing stress through rapid heating and cooling of the glass surface

Crystalline solids

have a regular atomic structure

crystalline solid

have definite geometric forms because of the orderly arrangement of their atoms

borosilicates

headlight and heat-resistant glass (pyrex); made by adding boron oxide to the oxide mix

Crystal glass

is made of lead oxide because the denser glass bends more light and creating the sparkling effect.

Normal line

is perpendicular to the glass surface

When a bullet penetrates a panel of glass, it leaves a crater shaped hole that

is smaller on the entrance side

intensive property

it is the same regardless of the size of a substance

As a bullet passes through the glass,

it pushes a cone shaped piece of glass out of the glass ahead of it

In examining the stress marks on the edge of a radial crack near the point of impact, the perpendicular end is always found to be:

located opposite the side from which the force of impact was applied

individual

match two pieces of broken glass together; very unlikely; at this time, the physical properties of density and refractive index are used most successfully for characterizing glass particles

What type of elements can give glass a specific color?

metal

temperature

most convenient reference points are freezing point and boiling point

Sink-float method

place glass particle into a mixture of miscible liquids, the mixture or temperature is altered until the glass suspends, Liquid mixture is measured with a density meter. Disadvantages:-same source can exhibit a slight range of densities, bromoform = toxic

Trona, processed into soda ash (Na2CO3)

primary sodium source, used to act as a fining agent, remove gas bubbles from the molten glass. Contaminant-Chloride, because iron is removed by re-crystallization.

The technique best suited for distinguishing among most paint formulations is:

pyrolysis gas chromatography

3 R rule

radial cracks form a right angle on the reverse side of the force

A crack in glass that moves outward from the point of impact like spokes on a wheel is called a

radial fracture

Radial fractures

radiate outward from the point at which the glass was struck

double refraction

refract a beam of light into two different light ray components

Bending of light waves as they change velocity is called:

refraction

The ratio of velocity of light in a vacuum to that in another medium (like water) is called the:

refractive index

Concentric fractures

roughly encircle the area around the point of impact, form usually if the pane is held firmly in place

stress markings

shaped like arches that are perpendicular to one glass surface and curved neatly parallel to the opposite surfaces

tempered glass

side and rear U.S. car windows; rapid heating and cooling of glass surfaces makes the glass stronger; fragments rather than splintering

Radiating fracture lines from a subsequent shot will...

stop at the edge of the fracture lines already present in the glass

stabalizers

strengthen the glass and make it resistant to water

Tempered glass

stronger than normal glass due to rapid heating and cooling.

refraction

the bending of a light wave as it passes from one medium to another

Refraction

the change in the direction of light as it changes speed when moving from one substance into another

Silicon dioxide

the chemical name for silica

amorphous solid

the constituent atoms or molecules are arranged in random or disordered positions

Exit holes

the larger of the holes made from a bullet

Becke Line

the line created as refracted light becomes concentrated around the edges of a glass fragment

Soda-lime glass

the most common glass, inexpensive and easy

match point

the observer will note the disappearance of the Becke line

concentric stress marks

the perpendicular end always faces the surface on which the force originated

radial stress marks

the perpendicular end is always found to be located opposite the side from which the force of impact was applied

Density

the ratio of mass to volume

refractive index

the ratio of the speed of light in a vacuum to its speed in a given substance; =velocity of light in vacuum/velocity of light in medium

dispersion

the separation of light into its component wavelengths or colors

entrance holes

the smaller of the holes made from a bullet

sand

the term applied to natural particles with a grain diameter between 1/16 mm and 2 mm; its color and contents is dependent upon the parent rock and surrounding plant and animal life

In order for physical evidence to be used effectively for aiding an investigator, it must first be photographed and tagged as evidence and turned over to the officer in charge of the crime scene.

true

Formers

they make up the bulk of glass

Density Gradients

tubes containing liquid layers of the heaviest density at the bottom up to the lightest density at the top. -Disadvantages:-tubes can not be reused, consume time and space

Laminated glass

two sheets of ordinary glass bonded together with a plastic film

Limestone (CaCO3) & Dolomite (CaMg(CO3)2)

used to contribute to chemical durability. Contaminant-Iron, no easy way to remove

Submersion Method is

used to determine a glass fragment's refractive index

Submersion method—

used when glass fragments found at the crime scene are small

Obsidian

volcanic glass

Lime

what is added wo prevent the glass from becoming permeable in water

Crystal stemware

what is made of leaded glass

Sand

what is the main ingredient of glass

wider on the exit side

when a bullet penetrates a panel of glass the crater is

Refractive Index

# The ratio of the speed of light in a vacuum to the speed of light in that medium # Typical glass has RI of 1.5 # 2 common properties of glass & other translucent materials are directly related to their RI # Light rays change direction when they cross interface from air to material (effect used in lenses) # Light reflects partially from surfaces that have RI diff from that of surroundings

Backward Fragmentation

# When glass broken - fragments fall in direction of force #Some fragments propelled back - due to concentric fractures

2 Successive impacts

# upon 2 successive impacts if glass still intact - can induce which impact occured first # cracks made by 2nd impact will TERMINATE if meet any fractures caused by 1st impact

Immersion method for determining R.I.

- glass particles immersed in a liquid whose refractive index is known. Use different known refractive index liquids and glass particles to create slides. When the glass particles disappear the R.I. of the glass is the same as the R.I. of the known liquid

Application of Refractive Index to Forensics

-Place the glass fragment into different liquids of known refractive indexes -The glass fragment will seem to disappear when placed in a liquid of the same refractive index

Glass

-is an amorphous solid and so has an irregular atomic structure -breaks in a variety of fracture patterns

ICP-MS advantages:

1000-fold lower detection limits, more rapid scanning, and sample is not introduced as a solution

D) the pressure exerted by a gas above the surface of its liquid.

7. Vapor pressure can be described as A) the temperature at which bubbles of vapor appear in a liquid. B) the pressure exerted on the Earth by the particles in the air. C) the temperature at which the vapor pressure of a liquid equals atmospheric pressure. D) the pressure exerted by a gas above the surface of its liquid. E) the pressure within the lungs during inhalation.

A human head hair is best characterized by......

A medulla that is absent or is less than 1/3 the overall diameter of the hair shaft

Annealing & how this affects the RI of Toughened Glass

ANNEALING # The process whereby glass is HEAT-TREATED to remove the stresses in it # RI measurements when used in conjunction with process of Annealing - used to distinguish between Ordinary & Toughened Glass # To anneal fragment of glass - heated to high temp for prolonged period of time (550 degrees for 1-24 hrs) then slowly cooled to room temp # Process removes stressed in glass & changes RI # As stress delib introduced into TOUGHENED GLASS during manufacture - fragment of this material will undergo sig GREATER CHANGE in RI on annealing than ordinary glass # Toughened glass typically shows increase of 140x10^-5 in RI

Human head hairs generally exhibit _______ medullae.

Absent

What individualizing features may help to identify a particular copy machine?

Accidental marks on the drum

B) is directly related to the number of moles at constant temperature and pressure

According to Avogadro's law, the volume of a gas A) depends only on the number of moles in the sample. B) is directly related to the number of moles at constant temperature and pressure. C) is inversely related to the number of moles at constant temperature and pressure. D) is inversely related to the number of moles at standard temperature and pressure. E) depends only on the temperature and pressure.

D) P increases; V decreases

According to Boyle's Law, as the _________ on a gas, the _________. A) P increases; T increases B) P decreases; V decreases C) T decreases; V stays the same D) P increases; V decreases

A) increases; increases

According to Gay-Lussac's Law, as the _________, the _________. A) T increases; P increases B) P decreases; T stays the same C) T decreases; V increases D) V increases; T decreases

Packaging

Affects the quality of the sample Different items require different packaging types Evidence can be lost Contamination - If the packaging isn't right - integrity of the sample is compromised Separate bags for different exhibits

What gives glass different colors?

Adding metal oxides

Who was the person that developed fundamental principles of questioned document examination?

Albert Osborn

Fluxes

Alkali Oxides- soda ash, pot ash, salt cake, to lower the melting temperature of the sand

What must questioned hairs be accompanied by?

An adequate number of control samples

A scalp hair specimen with significant root sheath material would indicate that the hair originated from which phase of growth?

Anagen

What are the three types of hair growth? Define each.

Anagen - hair that is growing Catagen - hair at rest Telogen - hair that is dying

In 1981, the greatest fraud in the history of publishing was perpetrated when the German publishing company Gruner and Jahr purchased the so-called "Hitler diaries". Three independent experts declared the diaries to be genuine but it was later revealed to be a hoax. What was the nature of the crucial evidence, discovered by German government scientists, which exposed the fraud?

Analysis of the paper The first three experts declared the diaries to be genuine using handwriting analysis. However, the German government scientists analysed the paper and found that it contained a chemical called "blankophor", a paper-whitening agent. Blankophor was not used in the manufacture of paper until 1954. Subsequent analysis of the ink established that the diaries were less than a year old. The book-bindings also contained man-made fibres and chemicals which were not available at the time the diaries were allegedly written

What will NOT be visible if a glass and a liquid has the same refractive index?

Becke Lines

Glass fracture & how Conchoidal marks on fractured surface can determine DIRECTIONALITY of impact

CONCHOIDAL MARKS # Curved shell like marks (J-shaped marks) # The curves form a RIGHT ANGLE to side of glass that was stretched during bending process & where crack started RADIAL CRACKS # stress marks are at right angle to the side OPPOSITE to where impact occurred CONCENTRIC FRACTURES # concentric fractures exhibit stress marks that form right angles to the SAME SIDE of glass where blow impacted # The ORIENTATION of stress marks in glass at point of penetration can help determine DIRECTION of impact

Hair cuttings

Can contain mitochondrial DNA

Glass comparison

Collect a known sample of glass from the scene of the crime, Package the known and questioned samples separately.

Collection of Glass Evidence: Fracture Fitting

Collect all or most of the pieces of glass from the frame, and mark the interior and exterior of the glass pieces

From what areas should standard/reference soils be collected when gathering soil evidence?

Collected at various intervals within a 100-yard radius of the crime scene, as well at the site of the crime scene

Light sensitive Glass

Colloidal particles of silver halide added to change color under certain conditions

What is the first step in a forensic soil comparison?

Color

Which of the following properties are examined when comparing two synthetic fibers?

Color Diameter Light dispersion The presence or absence of delusterants (a chemical agent, as titanium dioxide, used in reducing the sheen of a yarn or fabric)

What two morphological characteristics does a criminalist first compare when examining fibers with a microscope?

Color and diameter of the fibers

In comparing two hair samples, what aspects of the hair are the criminalist particularly interested in matching?

Color, length, and diameter

What characteristics does a criminalist's look for when comparing paint chips under a microscope? Which of these characteristics is most important in evaluating the significance of paint evidence?

Color, surface texture, and color layer texture. Color Layer Sequence is the most important.

When collecting document evidence, it is important to carefully protect the document in order to avoid:

Damage from any liquids

Do the two fragments of glass have the same source?

Density, R.I. Elemental Composition

What layer provides corrosion resistance for the automobile?

Electrocoat Primer

What is scientific data called when used in a courtroom setting to establish the connection of a person to a crime?

Evidence

Density of Glass

FLOATATION METHOD # This is the easiest way to compare densities of 2 small pieces of glass # 2 miscible (mixable) liquids are chosen (1 less and 1 more dense than than glass) # BROMOFORM & BROMOBENZENE # Tube filled with mixture of 2 liquids - then tiny pieces of glass inserted # Particles allowed to settle in liquid - then determine if settle at same lvl # Liquid heated (heat decreases density of liquid) - glass particles should move lower # If move to SAME SPOT then they have SAME DENSITY

DNA typing analysis is needed to identify the plant source of any pollen evidence found at the crime scene.

False

Glass is called an amphibious solid because its atoms are arranged in a random fashion

False

Questioned document examiners prefer to work with copies of a questioned document in order to avoid damage to the original material.

False

The premise in which Locard's Exchange Principle is based is that every criminal can be connected to a crime by dust particles carried from the crime scene.

False

The primary ingredient of glass is carbon dioxide

False

Float glass is prepared by cooling molten glass on a pool of liquid aluminum.

False Float glass is a sheet of glass made by floating molten glass on a bed of molten metal, typically tin, although lead and various low melting point alloys were used in the past. This method gives the sheet uniform thickness and very flat surfaces.

Gloves leave no prints

False Just like fingerprints, no two glove prints are alike. Investigators can find the type and maybe even the size of glove worn

GRIM

Glass Refractive Index Measurement: Varies the refractive index of the mounting medium by raising and lowering the temperature until the refractive index of the medium matches that of the glass (therefore the glass disappears, match point)

Electric Light Bulbs

Glass blown from a ribbon through holes and welded onto a glass base portion. Bulb is soda-lime-silicate, base is leaded glass

Low Velocity Impact Fractures

Glass bulges on the side opposite the force, causing that side to stretch and rupture first

Tempered Glass

Glass made stronger than ordinary window glass by introducing stress through rapid heating and cooling of the glass surfaces. Breaks into small squares, "dices." Used in side and rear windows of automobiles

Heat-strengthened Glass

Glass made stronger than tempered glass, Used for security applications

Coated Glass

Glass made with a film or coating added.Used for mirrors, solar shading, thermal insulation and electrical conductivity

Chemically Strengthened Glass

Glass made with treating surface with molten potassium salt. Used for eyeglass lenses

Laminated Glass

Glass which derives its strength from sandwiching a layer of plastic/polymer between two pieces of ordinary window glass. Windshields of automobiles. Bullet-resistant glass- made by increasing the number of alternating layers of glass and plastic

calcium carbonate

In the sand lab, you placed vinegar on the samples. What were you trying to determine?

Types of document examination

Indented Impressions Obliterated entries Impressions detected on altered cheque Printing money Chemical erasure Restoration of Documents

Properties of evidence that can be attributed to a common source with an extremely high degree of certainty is/are:

Individual characteristics Marks on an object produced by the random imperfections or irregularities on the surfaces of the tools used to manufacture the object Produced incidental to the manufacturing process and typically seen at microscopic level Can be produced on an object by use, abuse, and/or corrosion May be uniquely identifiable with a source

The fluid that is used to decolorize ink on a document is called:

Ink eradicator

What is the compositional class or product type?

Intentional features/Manufacturing process, Accidental features, Flatness/Curvature, Thickness, Color, Fluorescence (-Float glass can be readily identified, tin fluoresces in short-wave UV light, shows side of glass which was on bed of tin)

It _____ possible to determine when hair was last bleached or dyed.

Is

When glass is hit

It can stretch slightly

When a beam of light moves from a MORE DENSE medium (glass) into a LESS DENSE medium (air):

Its speed increases And bends light away from the normal line

When a beam of light moves from LESS DENSE medium (air) into a MORE DENSE medium (water):

Its speed slows Bends light toward the normal line

Mechanical Fit & why its considered as most Conclusive evidence when performing forensic exam of glass

MECHANICAL FIT # where its poss to individualise a piece of glass to a particular object # Occurs when piece of glass breaks into large pieces that have at least 1 intact edge that can be fitted to edge of another piece from same source GLASS # Hard & Brittle # Doesnt Deform when broken # Amorphous - no lattice points along which glass would fracture when subjected to force FRACTURES #fractures = random events # no 2 pieces of glass break in same manner # If good MECHANICAL FIT to 2 pieces of glass, can be concluded with high degree certainty that they were once JOINED STRESS MARKS # Fit aided by presence of stress marks along broken edge - as these also randomly generated & caused by force at breaking point

What aspects of the automotive painting process is helpful in forensic characterization of automobile paint? How is it helpful?

Manufacturers apply a variety of coatings to the body of a car. This adds significant diversity to automobile paint.

Density of glass is calculated by dividing the

Mass of a substance by its volume

Heat Fractures

Non-tempered glass will crack in a curved manner, with a smooth edge (mirror edge) and have no indication of point of origin

-X-ray Fluorescence (XRF) Advantages:

Nondestructive, little sample preparation, lower conc. of elements of higher atomic number can be measured than SEM/EDX

The reflective index is a tool used to study how light bends as it passes through

One substance and into another

Glass will break first on the weaker side, the side:

Opposite of the strike and radial fractures will result

2 factors that are responsible for PERSISTANCE of glass fragments on CLOTHING of suspect

PARTICLE SIZE # SMALLER particles (0.1-0.5mm) will transfer more readily to garments than larger particles TYPE OF FABRIC # WOLLEN fabrics retain same size of particle to greater extent # DENIM/sheer fabrics not retain the particle ACTIVITY OF SUSPECT #lots of movement/activeness may increase theshredd of glass fragments # Normally - majority lost within 1 hour - virtually all gone after 24 hours

What is PDQ and how is it helpful to forensic scientist?

Paint Data Query, a computerized database. Paints related to automobile make, model, and year.

Trace evidence analysis is used on which items?

Paint, fiber, glass, hair There are many subcategories and each has its own specialists. Forensic specialties include computational forensics, digital forensics (recovering evidence from digital and electronic media), forensic accounting, anthropology, aerial photography, geophysics, entomology, chemistry, psychology and psychiatry, odontology, optometry and a slew of others. Blood spatter analysis is another fairly new field, and the more we know the more there is to find out. Even DNA, which was the 'golden boy' of the science, has come under scrutiny, as it has been found to be fabricated in some cases.

Which of the following would be an example of a transfer medium?

Pen inks

What is studied in forensic palynology?

Pollens and spores One of the earliest cases involving the use of pollen analysis was in Austria in 1959. A man disappeared near Vienna but his body could not be found. Police had a suspect with a motive but no evidence to link him with the possible crime. The suspect's muddy boots were examined. Dr Wilhelm Klaus found a rare fossilised pollen which enabled him to pinpoint where the defendant must have walked to get the mud on his boots. When confronted with the identity of the location, the defendant confessed the crime and showed the police where he killed the victim and buried the body, both of which occurred in the precise region Klaus had pinpointed.

By examining fracture patterns, it is:

Possible to determine what side of the glass was hit

Handling Documents

Preserve the evidentiary potential of documents by maintaining their original condition and form Protect documents -Plastic pockets, bags, envelopes, manilla folders etc -Ensure envelopes are large enough for documents

Type of Fractures observed when a pane of glass is broken

RADIAL CRACKS # Formed first, on side of glass OPPOSITE to the destructive force # Cracks radiate across sheet from point of impact forming V-shaped portions of glass CONCENTRIC CRACKS # Occur afterwards on SAME side as force # Occur at approx the same distance from the point of impactin each V-shaped portion - form a rough CIRCLE around this point # If impact causes sufficient distortion in glass, POI will be encircled with another RING of concentric fractures

Optical Property of glass that's commonly used to characterise a glass fragment

REFRACTIVE INDEX # The ratio of the speed of light in a vacuum to the speed of light in that medium REFRACTIVE INDEX of a GLASS FRAGMENT determined by.... # Immersing it in Silicone oil (colourless liquid with high bp) # The glass fragment/surrounding liquid illuminated by a Monochromatic sodium light (589nm) # The boundary or BECKE LINE between the fragment and liquid observed through microscope as they're slowly heated # The BECKE LINE appears as a halo parallel to the border of the particle immersed in the liquid # If the BECKE line is OUTSIDE the perimeter of the glass fragment - the RI of the liquid is higher than that of the glass # If the BECKE line is INSIDE the perimeter of the glass fragment - the RI of the of the glass is higher than that of the surrounding liquid # As TEMP (of stage) RISES - the RI of glass changes v little but liquid drops at an appreciable rate # At a certain temp, when the RI's of the glass & liquid match - the BECKE (boundary) line will disappear # The RI of the liquid & glass at this temp can be found from a CALIBRATION graph by conducting similar exps using diff reference glasses, each of known RI # when established - RI of questioned & control glass fragments can be compared - with any questioned fragments with RI's not close to controls being eliminated as matches

The fracture pattern of glass usually has

Radial and concentric lines

Describe the methods of RECOVERY of glass evidence

Recovery of samples v important: # Hair # Clothing # Footwear # Vehicle HAIR - glass samples collected from # Combing # A cotton wool impregnated comb CLOTHING - glass on # Searching & Recovery # Tweezers # Brushing down ovr large piece of Brown paper AREAS of SPECIAL ATTENTION # Cuffs of sleeves # Turn ups of trousers # Soles of shoes # Pockets of garments/window frames at C.S

One method of determining if the evidence glass matches the glass from the crime scene is to compare the

Reflective index of the evidence glass to the refractive index of the glass from the crime scene

Glass examination

Refractive index is the bending and slowing of electromagnetic radiation as it passes through a transparent medium Glass Refractive Index Measurement • Compares glass recovered from suspects clothing or breaking implements with glass from the scene using refractive index • Measured using oil immersion/variable temperature method to 5 decimal places Inorganic analysis - Analysis of the percentages of inorganic elements present in the glass both bulk and trace

Types of Glass

SODA-LIME # Most common (also called flat glass) # Used for windowpanes BOROSILCATE # heat resistant glass # More resistant to breaking on rapid heating/cooling #used for lab ware/thermometers LEAD GLASS # high refractive index/high electrical resistivity # used for chandeliers/ costume jewelry TEMPERED GLASS # stronger than window glass # "dices" into small squares when broken # used for rear windows of automobiles LAMINATED GLASS # 2 layer of glass with high-stregth vinyl plastic film between layers - hold glass in place when breaks # used for windsheild

Physical characteristics of a glass fragment noted during MACROSCOPICAL & MICROSCOPICAL examination

SURFACE EXAMINATION # Info on source of glass fragments can be obtained by examining the Surface (ORIG SURFACE) # Can be examined under CMO (Common Main Objective) using mag x6 - x40 objective or angled LIGHT SOURCE # Locate & Note # MECHANICAL FIT, FRACTURE PATTERN # COLOUR, MARKS, DEPOSITS PITS, GROOVES # WEATHERING PATTERN SURFACE LUMINESCENCE # Flat glass made by FLOATATION method - molten glass floated on bed of molten TIN # TIN incorporated into surface layer - stereo-microscope used fitted with UV lamp (UV light of 254nm) Tests conducted in DARK room (gives GREENISH GLOW) # Used as SCREENING TECHNIQUE to identify Fragments which might've come from FLOAT surface SURFACE CONTOUR # Interference technique used to confirm surface is flat (interference between LIGHT REFLECTED from glass fragment & that from reference surface observed # Flat glass fragment - produce STRAIGHT DARK band interference pattern # Tilted surface - Dark & Bright bands # Curved surface - Curved/Circular interference bands

FAAS Disadvantages:

Sample is dissolved and destroyed in hazardous chemicals, Determine one element at a time so it is time consuming and tedious

FAAS Advantages:

Sensitive

What makes glass denser?

The addition of lead oxide

Silicon dioxide is

The chemical name for silica

Which hole is larger? ( exit side or entrance side)

The exit side of the hole is larger than the entrance side of the hole

When a beam of light moves from one medium into another:

The speed changes The direction bends

Which characteristic of fragments of metal (including bullets and bombs), glass, ceramics and even skid marks on exposed surfaces can be used to identify the origin of these materials?

Trace element composition The very small, 'trace' amounts of a large number of chemical elements can be used as a 'fingerprint' to identify the origins of a material in a forensic case. For example, glass is made from silica (silicon and oxygen) but contains very small amounts (parts per million) of uncommon elements like rubidium, barium, strontium and uranium (and many others). The exact composition depends on the origin of the source material (e.g. which mine it came from) plus the manufacturing process and equipment. The ratios of these trace elements to each other is diagnostic. One of the most famous cases where such information has been used is the unsolved question of who shot President Kennedy. Bullet fragments taken from the scene (including the victims) were later analyzed for silver and antimony content. Evidence presented to the 1977 US House of Representatives Select Committee on Assassinations on the trace concentrations of these metals demonstrated that only two bullets hit the car and its occupants. This finding was consistent with the Warren Commission findings but did not prove them to the exclusion of other interpretations. This same trace element 'fingerprinting' has been used to identify the source of metal fragments used in terrorist bombs and hit and run accidents, the location from where soil samples on a suspect's shoes originated and the provenance of old coins, amongst a myriad of other applications

Lord Louis Mountbatten, a cousin of Queen Elizabeth II, was blown to pieces in 1979 when an IRA bomb exploded on his yacht. How did police link the murderer, Thomas McMahon, to the crime scene?

Trace evidence of nitroglycerine Matching paint samples Matching sand samples The evidence against McMahon included a tiny speck of green paint on his boot which matched the paint on the yacht, the sand on his boots matched that found near the beach near where the boat was launched and traces of nitroglycerine were found on his clothes which were matched to the bomb.

A fracture in glass always terminates at an existing line of fracture

True

normal line

a line drawn perpendicular to the interface surface of two different media

Refraction index

a measure of how light bends as it passes from one substance to another

density

a physical property of matter that is equivalent to the mass-per-unit volume of a substance; D=m/v; intensive

annealing

a process of slowly heating, then cooling a substance; used to distinguish tempered from nontempered glass particles

weight

a property of matter that depends both on the mass of a substance and the effects of gravity on that mass

Why is glass commonly found at crime scenes?

because it is easily broken, transferred and retained by persons and objects at the scene.

Why is it usually impossible to obtain fingerprints from textiles such as fabric, clothing and carpet?

because textiles are very absorbent Textile fibres absorb the oils and moisture present on the fingers and are very porous. There are three types of fingerprints - latent, visible and plastic (molded). - Latent prints are invisible to the eye and are usually obtained from hard surfaces such as glass or wood. - Visible prints are those that result from fingers stained with blood, ink, paint or similar. - The plastic or molded print is an impression made on a soft surface like putty, soap or cheese.

A significant difference in either density or refractive index proves that the glasses examined do not have a common _________

origin

hot stage

special apparatus for heating a liquid into which glass is immersed to determine its refractive index

side windows

which windows in autos are made from tempered glass

soda-lime glass

window and bottle glass; contains sodium, calcium, magnesium, and aluminum

laminated glass

windshield of U.S. cars; one layer of plastic sandwiched between two pieces of ordinary window glass

Amorphus

without shape or form

Types of Examination

• Handwriting / Signatures • Indented Impressions • Alterations / Obliterations / Erasures • Ink / Paper Analysis • Document Restoration • Physical Match • Photocopiers / Printers / Office Equipment • Printing / Counterfeit Comparisons • Typewriters • Stamp Impressions • Fraud, Theft • Homicide / Suicide • Drug Traffic / Clandestine Labs • Sexual offences • Threats and Extortions • Blackmail • Arson, Bombings