Glass & Soil Analysis

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Amie Neal
6 years ago
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1 Glass & Soil Analysis

2 Glass Evidence Class evidence Glass evidence is considered trace evidence Most common substance submitted for trace analysis Valuable because it does not degrade easily

3 Characterizing Glass Type of glass Density by flotation Refractive index

4 Type of Glass There are many different types of glass. This information is used to determine where the glass evidence was a part of initially Ex: The glass of a light bulb is made differently and has a slightly different chemical composition than glass from eyeglasses

5 Density by Flotation Glass is floated in liquid bromoform or bromobenzene Depending on how the piece of glass floats/sinks in each substance will help determine its density Once density is known, this is used to find the composition of the glass, helping to determine where the glass is from (a headlight, a window, etc.)

$Refractive Index Light bends when it enters a new material. Knowing this, we can measure how much the light bends when it enters the piece of glass evidence.$

6 Refractive Index Light bends when it enters a new material. Knowing this, we can measure how much the light bends when it enters the piece of glass evidence. This value is then used to find the refractive index for that particular piece of glass. Each type of glass has a specific refractive index. For Example: Crown Glass (light bulbs) = 1.52 Flint Glass (telescope lens) = 1.65

7 How does Glass break? Forensic Fracture Analysis

8 70 % of glass Sprays forward Fractured Glass 30 % of the glass Will spray back on The shooter

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

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

$to one side of glass] For radial fractures (radiating from the center): - the direction of the force is on the same side as the tangential parts of the rib$

11 A determination of the direction of force in breaking a window pane: -direction of the rib marks [stress marks on broken edges of glass that are perpendicular to one side of glass] For radial fractures (radiating from the center): - the direction of the force is on the same side as the tangential parts of the rib marks.

12 Projectiles High velocity smaller, rounder holes Low velocity larger, more irregular holes Very low velocity - Shatters

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

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

16 Which one was made first? B was made first

$A, B, C - Radial fractures of B stop at those of A, C s stop at B s$

17 A, B, C - Radial fractures of B stop at those of A, C s stop at B s C, B, A - Radial fractures of A stop at those of B, B s stop at C s

18 The Baltimore Rapist A serial rapist in Baltimore broke into a house where he was confronted unexpectedly; the man panicked and dove through a window to get away.

19 Police eventually caught him several blocks away from the scene. Samples of glass slivers were taken from his clothes and linked to the broken window from the scene for evidence.

20 But there were other slivers of glass in his clothes that did not match the glass from the broken window. Police investigated other rape scenes in which the perpetrator broke a window to get in and found that the glass linked this suspect to three other rapes!

21 Justice is served! The glass told his story!! Trace evidence doesn t lie!

22 Soil as Trace Evidence What is soil? Soil is a complex mixture of different sized mineral grains from the weathering of rock and organic material. It is also composed of decay of vegetation and animals. Anything mixed in the soil such as bits of glass, paint, metal, etc. can be used in forensic analysis

soil: Sand: Caused by extreme weathering Dark organic

23 Properties of Soil The proportion of sand, silt, clay and organic matter determines the properties of the soil: Sand: Caused by extreme weathering Dark organic soil: Caused by slow decomposition of vegetative matter

may have traces of zinc in the soil in their shoes.

24 How can soil help catch a suspect? Example: If a victim was found near a chain-link fence, the suspect may have traces of zinc in the soil in their shoes. If a victim was found outside a home with asphalt shingles, the dirt directly below would show traces of shingle stones

25 If a victim was found in a yard with potted plants, the potting soils often contain slowrelease mineral pills. Continued

Walter Osborne had driven along the dirt road to Coors s ranch in the Rocky Mountains

26 The Coors Kidnapping Adolph Coors III, chairman of the Coors Brewing company, was kidnapped in the winter of Walter Osborne had driven along the dirt road to Coors s ranch in the Rocky Mountains of Colorado. While Coors was on his way to work, Osborne forced Coors into his yellow Mercury sedan at a bridge over a creek and fatally wounded him.

27 Victim: Adolph Coors III Suspect: Joseph Corbett, Jr. Aka Walter Osborne

28 Eight days after kidnapping Osborne s burned out car was found 8 days later near a municipal dump on the New Jersey Shore. Evidence in the car led investigators to Walter Osborne.

29 Seven months after kidnapping Coors s body was found about seven months after the kidnapping at another dump high in the Rockies. Walter Osborne was also found a couple of weeks later. But he wasn t confessing

30 Dirt from the undercarriage of the car: Soil from the Rocky Mountains area proves the car was in the Rockies. Light gray sand match the soil In the Coors s ranch area Dust that matches the soil at the dump where the body was found. Rounded sand grains that match the soil found at the New Jersey dump where the car was found.

31 Justice is served! The soil not only told his story, but the sequence of soil evidence was undeniable! Trace evidence doesn t lie!!!

Properties of Matter Review: Density

Properties of Matter Review: Density Density is mass per unit of volume Density = mass volume Is an intensive property of matter: remains the same regardless of the size of the object Observe whether an