4 Mystery Pictures Week 3 Monday T Trimpe 2006 httpsciencespotnet Can you identify the mystery items All the items are associated with crime scene investigations 1 2 3 4 ID: 734364
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Slide1
Daily CSI
CSI Challenge
#4
Mystery Pictures
Week 3 - Monday
T. Trimpe 2006 http://sciencespot.net/Slide2
Can you identify the mystery items?
All the items are associated with crime scene investigations.
1
#2
#3
#4
#Slide3
The answers are …
#1
#2
#3
#4Slide4
Glass Challenge
Assignment: Carefully watch the video clip and answer the following questions:
1. What are some of the purposes of laminated glass?
What does in between the two pieces of glass?
Is the middle layer clear as they put it between the glass?Does Cardinal test its glass ?
Laminated Glass by CardinalSlide5
Glass Challenge
Assignment: Carefully watch the video clip and answer the following questions:
Name 3 applications of electronic ready glass.
A Day Made of Glass – Made by Corning
lSlide6
Daily CSI
Test
Time
Spot the Differences Slide7
Find the 6 differences between the two pictures.
Source: http://www.slylockfox.com/arcade/6diff/index.htmlSlide8
The answers are …
Source: http://www.slylockfox.com/arcade/6diff/index.html
Answers: Apple stem, exclamation point, keyhole, girl’s paper, clock, pencilSlide9
Glass Challenge
Assignment: Carefully watch the video clip and answer the following questions:
1. What are some items that are made of tempered glass?
How does tempered glass shatter?
What did it take to break the tempered glass?What area of the tempered glass is the strongest?
Tempered Glass Tests
4:28Slide10
Glass ChallengeSlide11
Glass Challenge
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What side of the glass
Did the force come from; the Top or the bottom?What type of glass is in each of the windows?Slide12
Glass Challenge
Assignment: Carefully watch the video clip and write down 3 things you learned about glass production.
How Glass is Made – Part 1
How Glass is Made Part 1
3:56
How Glass is Made – Part 2
How Glass is Made - Part 2
2:44
Float Glass Manufacturing
ProcessFloat Glass Manufacturing Process 4:09How float glass is made before it goes into Mercer windows How float glass is made before it goes into Mercer windows 3:25Slide13
Chapter 14
Glass“There is no den in the wide world to hide a rogue. Commit a crime and the earth is made of glass.”
—Ralph Waldo EmersonSlide14
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13Glass Analysis
The difference between physical and chemical properties. How glass can be used as evidence.
How individual evidence differs from class evidence. The nature of glass. How to use the properties of reflection, refraction, and refractive index to classify glass fragments.
Students will learn: Slide15
Daily Challenge 2
Tempered Glass Tests 4:28Laminated Glass by CardinalKendall/Hunt Publishing Company
14Slide16
How Glass is Made – Part 1
How Glass is Made Part 1 3:56How Glass is Made – Part 2 How Glass is Made - Part 2 2:44Float Glass Manufacturing ProcessFloat Glass Manufacturing Process 4:09
How float glass is made before it goes into Mercer windows How float glass is made before it goes into Mercer windows 3:25Kendall/Hunt Publishing Company
15Slide17
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16GlassGlass is a very common material in our environment.
Many products are made from glass, such as:WindowsBottlesEyeglasses
headlightsSlide18
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17Investigators can use glass fragments found at a crime scene. . .
Glass that is broken and shattered into fragments and minute particles during the commission of a crime can be used to place a suspect at the crime scene.Slide19
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18Chips of broken glass from a window may be lodged in a suspect’s
shoes or garments during the act of a burglary, or particles of headlight glass found at the scene of a hit and run accident may offer clues that can confirm the identity of a suspect vehicle. Slide20
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19Glass as Evidence Class And Individual Evidence
Individual evidence - If the fragments can be pieced together, like the pieces of a jigsaw puzzle.
Most often though, glass shatters into so may fragments that piecing them together is impossible, thus the glass must be considered class evidence.Class characteristics include physical and chemical properties such as refractive index, density, color, and chemical composition. Slide21
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20How can glass be used as evidence?
The forensic scientists must use as many physical properties of glass as possible to characterize fragments and link the fragments from the crime scene to a suspect.Also by studying the
fracture patterns of glass, an investigator can recreate a sequence of events to aid in reconstruction of a crime.Slide22
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21Glass
Is a hard, brittle, amorphous substance, usually transparent, and is composed primarily of silicon oxides mixed with various metal oxides.
Glass is found in nature as sand. It is heated.It is mixed with
chemicals to change its properties.It is sometimes mixed with metals for added color.
When sand is mixed with other metal oxides, melted at high temperatures, and then cooled to a rigid condition without crystallization, the product is glass.Slide23
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22The First Glass
Is thought to have been made in Mesopotamia about 2500 BC.The technology was found in Egypt as small brightly colored vessels about 1450 BC.The Romans were master glassblowers and produced beautiful works of art in glass.Slide24
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23Glass was first made by melting sand (silica) and ashes (soda Na
2CO3).The soda acts as a flux to reduce the melting point of silica.
Lime (CaO) is added to make the sodium silicate glass water insoluble.Slide25
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24The Main Ingredient
The main ingredient in ordinary glass is silicon dioxide (SiO2)
or more commonly referred to as sand.Even though sand is plentiful, glass used to be relatively rare and expensive because of the high temperatures (higher than 3,000 degrees Fahrenheit) required to turn sand into glass.Slide26
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25
Glassmakers add various ingredients to modify the properties of glass.Boron oxide (B2
O3) increases the temperature stability of glass so that it can be sued as ovenware, as in Pyrex.Lead (Pb) increases the density and refractive index so that the glass sparkles, as with leaded crystal.Slide27
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26By adding soda (Na
2CO3) to the sand, its melting point and viscosity are both lowered, making it much easier to work with.Lime
(CaO) is added to the sand and soda mixture so that the “soda-lime” glass will not dissolve in water.Slide28
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27Families of Glass
Glass can be classified into families.The families differ widely in chemical composition and physical properties.There is far less variation of properties within families than between them.Slide29
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28Common Types
Soda-lime—used in plate and window glass, glass containers, and electric light bulbs
Soda-lead—fine table ware and art objectsBorosilicate—heat resistant, like Pyrex
Silica—used in chemical wareTempered—
used in side windows of cars
Laminated
—
used in the windshield of most carsSlide30
There are three main chemical types of glass of interest to forensic scientists
.a. Fused silica
b. Soda lime (soft)c. BorosilicateSlide31
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30Fused Silica
Glass made from pure sand is known as quartz, or fused silica.
This is the purest type of glass.It is the strongest and most thermally stable form of glass known.If a piece of fused silica is heated in a flame until it glows red and then plunged into ice cold water, it will not crack.
The windows in the space shuttle are made of fused silica.Slide32
Eventually someone discovered that adding other chemicals could lower the melting point of pure sand so that so much heat was not needed.
A mixture of soda (Na2O) and lime (
CaO) lowered the melting point of the mixture to about 1300 degrees Fahrenheit and produced the glass known as
soda lime or soft glass.Slide33
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32Soda Lime Glass
Is relatively cheap to make and is used in many applications such as windows, bottles, jars, and most glass items that do not have to be heated.
Melting point is 1300 degrees FIs not very stable thermally and tends to shatter when heated.
The common metal oxides found in this type of glass are sodium, calcium, magnesium, and aluminum.Slide34
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33Borosilicate Glass
The lime is replaced with boron oxide (B2O3), so it contains soda, boron oxide, and sand.The resulting mixture melts at about
1650 degrees Fahrenheit) and produces a glass that is more thermally stable than soda lime glass, but not as stable as fused silica glass.Slide35
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34Borosilicate Glass
Borosilicate glass can be heated and will not crack (it will however, crack if it is heated and then plunged into cold water)Is used for
cooking and lab glassware.Borosilicate glasses are sold under the trade names Pyrex, and Kimax.Slide36
The Color of GlassSlide37
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36Small amounts of elements can influence the color of glass.
Natural color of glass – is slightly green because of iron oxide in the sand.Purple – by adding manganeseBrown – by adding iron and sulfur
Green – by adding chromiumBlue – by adding cobaltRed- by adding gold or copper dustYellow – by adding silverWhite milk glass – by adding
tinSlide38
Glass Processing
The three different types of chemical glass can be manufactured into final products using one of three different processes.
A. Flat/Float Glass
B. Laminated GlassC. Tempered GlassSlide39
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38A. Flat
GlassIs probably the most common glass and is used for windows.Is made from soda lime glass and is sometimes referred to as
annealed glass.After flat glass is made, it is heated and then slowly cooled by a process known as annealing, which removes any thermal stress in the glass and makes it stronger.Slide40
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39Flat Glass
Can be made by rolling glass between metal drums to produce a glass known as sheet or plate
glass.This glass picks up many distortions from the drums, and for this reason, the process has been replaced by the float method.Slide41
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40A. Float
GlassIs distortion free flat glass.Is produced by using a bath of molten tin
to support the glass as it is being manufactured.This method produces distortion free glass, which is then annealed (heated and then slowly cooled).Flat glass absorbs ultraviolet light on one side because of its contact with
tin. Slide42
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41A new discovery . . .
In 1903 Edouard Benedictus, a French scientist, was working in his lab when he accidentally knocked over a glass flask and it fell to the ground.The flask broke, but the glass stayed in place because its surface was covered with a thin film of cellulose nitrate, a liquid plastic.Slide43
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42In the same week . . .A newspaper in Paris ran an article about the increasing number of automobile accidents in the city.
The main cause of injury and death was a result of drivers and passengers being cut by windshield glass.Slide44
Edouard
realized that a thin film of plastic could keep all the pieces of glass intact even if the windshield were broken.And so was the birth of safety glass. . . .How Its Made - WindshieldsSlide45
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44B. Laminated glass
Sometimes referred to as safety glass
Normally has three layersTwo layers of soda lime glass with a thin film of plastic sandwiched between.The front windshield of all cars sold in the United States must be made of safety glass/laminated glass.The term safety is normally stamped right on the glass.Slide46
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45Tempered Glass
Is Soda lime glass that is heated to about 1150 degrees Fahrenheit, at which point it softens.Jets of air are blown against the outside surface of the glass rapidly
cooling it.The surface of the glass solidifies before the inside, creating tension, and this makes this glass very strong.Tempered Glass TestsSlide47
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46Because this is actually considered a safety feature, the side and back windows of many cars are made of tempered glass.
In an accident, these windows disintegrate into many tiny and sometimes square particles that are not likely to cut anyone.Slide48
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47Tempered Glass
Because of this safety feature, tempered glass is used in the side and rear windows of auto’s made in the U.S. as well as in the windshields of some foreign made cars.Slide49
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48However,
Because windows help keep people from being ejected from vehicles, many groups are pushing the government to require that all automobile windows be made from laminated glass.Slide50
Glass ComparisonSlide51
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50Physical Properties that can be used for glass comparison
Density—mass divided by volumeRefractive
index (RI)—the measure of light bending due to a change in velocity when traveling from one medium to anotherFracturesColor
ThicknessFluorescenceMarkings—striations, dimples, etcSlide52
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51
Many of the properties of glass cannot be measured on small fragments and are of little concern to the forensic scientist.However, the most important are:Density = m/v
Refractive indexThese can be measured and serve as class evidence. Slide53
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52The density and refractive index of glass can vary according to the chemical type of the glass and the manufacturing process.
The forensic scientist can determine the refractive index and density and tell what type of glass a fragment is made of.Slide54
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53Density
Type of Glass
Density
window
2.46-2.49
headlight
2.47-2.63
pyrex
2.23-2.36
lead glass
2.9-5.9
porcelain
2.3-2.5Slide55
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54The density of glass fragments can be determined by the flotation
method
Flotation gives a precise and rapid method for comparing densities of glass.Slide56
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55Flotation
A small shard of glass is put in a vial filled with bromoform.Since the density of bromoform is greater than that of glass, the shard floats.Next, either bromobenzene or ethanol is added drop by drop and the solution mixed with each addition.Slide57
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56When the density of the mixture is the same as that of the glass, the shard neither sinks nor floats but is
suspended about halfway between the top and bottom of the solution as if it were weightless.Slide58
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57The mass and volume of the solution are then measured using a graduated cylinder and an electronic balance.
Dividing the mass of the solution by the volume of the solution gives the density of the glass.Slide59
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58The Refractive Index can be determined by the immersion
technique also known as a “hot stage microscope technique”Refractive index - is a
physical property of glass.Refractive Index - can be determined by making the fragment disappear in a liquid of a known refractive index.Is a measure of how much the glass bends light.To determine the refractive index, a glass shard is placed on a microscope slide and a drop of oil with a refractive index higher than that of the glass is added.
As the temperature is increased, the refractive index of the oil decreases.Slide60
The Grim 2
This procedure is carried out in an apparatus known as a hot stage.The glass is immersed in a high boiling liquid – usually a silicone oil, and heated at the rate of 0.2 C per minute until the match point is reached.
The instrument is known as GRIM 2 (Glass Refractive Index Measurement)The FBI has a database with approximately 2,000 refractive index values.Slide61
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60When the refractive index of the oil and the glass are exactly the same (known as the “match point”), the lines of light pass straight through and the shard disappears
.Index of Refraction: Disappearing Glass and Disappearing Gel, 2010Slide62
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61The Becke
Line is useful when examining refractive index. The
Becke line is a “halo” that can be seen on the inside of the glass on the left, indicating that the glass has a higher refractive index than the liquid medium. The Becke line as seen on the right is outside of the glass, indicating just the opposite. When the halo disappears, it means the glass has the same refractive index as the liquid at that temperature.Slide63
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62Refractive Index
Liquid
RI
Glass
RI
Water
1.333
Vitreous silica
1.458
Olive oil
1.467
Headlight
1.47-1.49
Glycerin
1.473
Window
1.51-1.52
Castor oil
1.82
Bottle
1.51-1.52
Clove oil
1.543
Optical
1.52-1.53
Bromobenzene
1.560
Quartz
1.544-1.553
Bromoform
1.597
Lead
1.56-1.61
Cinnamon oil
1.619
Diamond
2.419Slide64
Glass Fracture PatternsSlide65
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64http://www.aetv.com/crime-360/video/index.jsp?bcpid=760102388001&bckey=AQ~~,AAAAAEK2ejU~,Ai-tVL3JZg1X7tNHxqFBCx40w6oWy9sv&bclid=1459293923&bctid=20817496001
Crime 360 Bullet TrajectoriesSlide66
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65Investigators can sometimes reconstruct a crime using glass fracture patterns.
How the cracks are formed, what shape they have, and whether the breakage was caused on the inside or outside are clues as to what happened.Slide67
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66Glass is slightly flexible, but when forced to its elastic limit, it will break or fracture.
Studying the break or fracture pattern will provide information on the force and direction.Glass’s elasticity also causes some glass fragments to recoil backward toward the direction of force (blowback), thus possibly leaving clues in the perpetrators clothing, hair, etc.Slide68
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67Projectiles
The penetration of ordinary window glass by a projectile, whether it is a bullet or a stone, produces a familiar fracture pattern in which cracks both radiate outward and encircle the hole.Slide69
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68When a high speed projectile passes through a glass window, it punctures the glass rather than causing the whole pane to shatter.
The entrance side of the window shows a smaller more regular hole.The
exit side of the window shows a larger, more irregular hole.Slide70
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69Bullet. . . or no bullet?
Often it is difficult to determine just from the size and shape of a hole in glass whether it was made by a bullet or by some other projectile.Ex – a small stone thrown at a high speed against a pane of glass will often produce a hole very similar to that produced by a bullet.A large stone can completely shatter a pane of glass in a manner closely resembling the result of a close-range shot.
However, the presence of gunpowder deposits on the shattered glass fragments does point to damage caused by a firearm.Slide71
1. radial 2. Concentric
Usually 2 distinct types of fractures will occur when a projectile hits glass:Kendall/Hunt Publishing Company
70Slide72
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71A. Radial Fractures
1. Radial - The radiating lines are appropriately known as radial
fracturesThey begin at the hole and radiate out like spokes on a wheel.Radial fracture lines radiate out from the origin of the impact; they begin on the opposite side of the forceSlide73
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72Radial fractures
3 – R Rule – Radial cracks form a Right
angle on the Reverse side of the force. Always stop on existing fracture lines. They can be used to determine the order in which multiple gunshots have been fired through a window.Slide74
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73Slide75
Conchoidal
LinesAre the stress lines that can be seen when glass is held sideways. They are curved and can be associated with that of a seashell.The 3 R rule may be used to determine the direction of travel of a projectile.
One end will be more perpendicular which according to the 3R rule, would be the right angle – which would be on the reverse side of the force.These lines may be seen more vividly with polarized light.Kendall/Hunt Publishing Company
74Slide76
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75Slide77
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76Slide78
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77Slide79
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78Slide80
B. Concentric Fractures
Concentric - The circular lines are termed concentric
fractures.Concentric fracture lines are circular lines around the point of impact; they begin on the same
side as the forceKendall/Hunt Publishing Company79Slide81
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80Which one is a radial fracture and which one is a concentric fracture?
ABSlide82
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81Slide83
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82Slide84
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83Slide85
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84Order of Fractures
When there have been successive penetrations of glass, it is frequently possible to determine the sequence of impact by observing the existing fracture lines and their points of termination.Slide86
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85Slide87
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86Slide88
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87Which one happened first?
ABSlide89
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88Slide90
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89Radial fractures were used to help determine what really happened in a case that occurred several years ago. . .
Two men, who were acquaintances, were drinking and watching a football game on the television.They got into a heated argument and one left saying that he was going to get his gun and come back.When police responded at the scene they found one man, with a gun, shot dead on the lawn outside the house. . . .Slide91
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90The other man was inside the house, also with a gun.
He told police that he saw, through his living room window, the other man waving a gun.He then went and got his own gun.He said the man outside fired his gun into the house and that he fired back in defense and shot and killed the man on the lawn.Slide92
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91The police took the living room window to the crime lab to see if the physical evidence could corroborate the man’s story.Slide93
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92There were two holes in the window. . .
Bullet hole A had a larger hole on the outside of the window.Bullet hole B had a larger hole on the inside of the window. Bullet hole A – from person standing inside or outside of the house?
Bullet hole B - from the person standing inside or outside of the house?Slide94
This meant that bullet hole A was from the shot fired by the man inside the house.
Bullet hole B was from the shot fired by the man standing on the lawn outside the house.Kendall/Hunt Publishing Company
93Slide95
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94Radial lines emanating from bullet hole B end on radial fractures from bullet hole A.
Which bullet hole was present first? Slide96
Bullet hole A was present first.
So what was the real truth? Who fired first?Kendall/Hunt Publishing Company
95Slide97
This meant that the man inside the house was the first to fire.
The man outside was already fatally wounded when he fired a shot back into the house.Kendall/Hunt Publishing Company
96Slide98
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97Investigators can sometimes use holes in a window to pinpoint the location of the shooter if a projectile leaves a second marks at some length behind the first one.
For example, fixing a laser pointer at the second mark so that the beam shines through the initial hole illuminates a probable point of origin.The investigator must take into account any factors affecting the trajectory, such as wind, distance, and type of projectile.Slide99
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98However, as the velocity of the penetrating projectile decreases, the irregularity of the shape of the hole and of its surrounding cracks increases,
At some point the hole shape will provide no assistance for determining the direction of impactSlide100
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99Reconstruction of GlassSometimes a forensic scientist must reconstruct an entire window from the fragments left at the crime scene.
This can be a daunting task if there are many pieces to fit together Slide101
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100Two techniques used to simplify the task involve:
A. ultraviolet light B. polarized lightSlide102
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101
Ultraviolet light is absorbed by the side of the glass that was in contact with the liquid tin used in the flotation method of manufacturing flat glass.
This allows the forensic scientist to arrange all the glass fragments from a window with the same side up.Slide103
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102
Polarized light is then used to make the stress lines in the glass visible.These lines can be used to help align the pieces of glass to reconstruct the window and can even be used to determine if a piece of glass found on a suspect matches the glass from the crime scene.Slide104
Collection and Preservation of Glass EvidenceSlide105
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104Preservation
The glass fragments should be packaged in solid containers to avoid further breakage.If the suspect’s shoes and/or clothing are to be examined for the presence of glass, the whole article should be individually wrapped in paper and transmitted to the lab.Slide106
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105Collecting the Sample
The glass sample should consist of the largest amount that can be practically collected from each broken object and packaged separately. The sample should be removed from the structure (e.g., window frame, light assembly). The inside and outside surfaces of the known sample should be labeled if a determination of direction of breakage or reconstruction of the pane is desired.
—Forensic Science CommunicationsSlide107
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106
When multiple broken glass sources are identified, it is necessary to sample all sources. A sample should be collected from various locations throughout the broken portion of the object in order to be as representative as possible.