Chapter 19 glass soil_new design

2nd Edition, CRC Press, 2nd Edition, CRC Press, Jay A. Siegel and Kathy Jay A. Siegel and Kathy MirakovitsMirakovits 11

Forensic Science: Forensic Science: The BasicsThe BasicsChapter 19Chapter 19

Glass and Soil Glass and Soil

Jay A. SiegelJay A. SiegelKathy MirakovitsKathy Mirakovits


GlassGlass

• An amorphous solidAn amorphous solid• In pure form is made up of silicon and In pure form is made up of silicon and

oxygen molecules (SiOoxygen molecules (SiO22))nn

• No ordered structure and no crystal habitNo ordered structure and no crystal habit• High melting point - over 2000 High melting point - over 2000 00CC• Hard & brittle like a solidHard & brittle like a solid• No regular order to chemical bonds like a No regular order to chemical bonds like a

liquidliquid


Types of GlassTypes of Glass• Float glass or soda lime Float glass or soda lime

glass- windows, picture glass- windows, picture frames, flat glass objectsframes, flat glass objects• SiOSiO2 2 with sodium carbonate with sodium carbonate

(Na(Na22COCO33 and calcium oxide CaO) and calcium oxide CaO)

• Tempered glass- safety glass, Tempered glass- safety glass, auto glass, shower doors and auto glass, shower doors and plate glass windows in storeplate glass windows in store• Same chemical makeup as soda Same chemical makeup as soda

lime glass, but top layer is lime glass, but top layer is cooled first causing internal cooled first causing internal stresses. When broken this stresses. When broken this glass fractures into small blunt glass fractures into small blunt pieces.pieces.


Types of GlassTypes of Glass• Borosilicate glass- lab Borosilicate glass- lab

glassware, kitchen items glassware, kitchen items (Pyrex)(Pyrex)• SiOSiO2 2 with Boronwith Boron

• Tinted glass- has colorants Tinted glass- has colorants that reduce glare / heat that reduce glare / heat penetration or for decorative penetration or for decorative useuse• SiOSiO2 2 with additives/colorantswith additives/colorants

• Leaded glass (crystal)- wine Leaded glass (crystal)- wine glasses, fine dining, figurinesglasses, fine dining, figurines• SiOSiO2 2 with lead oxidewith lead oxide


Glass as Forensic EvidenceGlass as Forensic Evidence

• Glass is forensically importantGlass is forensically important• It is found at most crime scenesIt is found at most crime scenes• It can be carried away from scene undetectedIt can be carried away from scene undetected• It is stable, does not decayIt is stable, does not decay• As class evidence contributes to the pool of As class evidence contributes to the pool of

evidenceevidence• Important to collect proper known samples Important to collect proper known samples

so incidental glass can be eliminatedso incidental glass can be eliminated


Fracture MatchFracture Match

The vertical white lines are stress marks in two eyeglass lenses. Notice how the stress marks align, an individual characteristic.

• Glass generally Glass generally classclass evidence, except evidence, except when a fracture match is found, which is when a fracture match is found, which is considered to be an considered to be an individualindividual characteristiccharacteristic

• Microscopic characteristics can assist in Microscopic characteristics can assist in making decision about suspected matchmaking decision about suspected match

• Random stress patterns and breaks are Random stress patterns and breaks are uniqueunique

Reassembled Molotov Cocktail


Analyzing Broken GlassAnalyzing Broken Glass• Broken glass analysis is forensically Broken glass analysis is forensically

important to the reconstruction of events important to the reconstruction of events in a criminal actin a criminal act

• Analysis can include:Analysis can include:• The sequence of the fractures – order of eventsThe sequence of the fractures – order of events• The direction of the force which caused the The direction of the force which caused the

fracture – did the break occur from the inside fracture – did the break occur from the inside or outsideor outside

• The identity (type) of a small piece of glass – The identity (type) of a small piece of glass – soda lime glass, borosilicate, tempered, or lead soda lime glass, borosilicate, tempered, or lead crystalcrystal


Sequencing FracturesSequencing Fractures• Fracture lines: Radial and ConcentricFracture lines: Radial and Concentric

• Radial fracture lines occur first extending outward from Radial fracture lines occur first extending outward from the break point, produced when the opposite side of the break point, produced when the opposite side of impact fails firstimpact fails first

• Concentric fracture lines form a circle about the break Concentric fracture lines form a circle about the break point and are produced by the side of impact failing firstpoint and are produced by the side of impact failing first

A B

Radial Fractures

Concentric Fractures


Sequencing FracturesSequencing Fractures• Radial lines always end in existing radial Radial lines always end in existing radial

lineslines• Order in photo: A->B->COrder in photo: A->B->C

A

B C


What Are The What Are The Possible Fracture Sequences?Possible Fracture Sequences?

A

B

C

D

E

It can be noted:

B was first

C was after E

E was after A

D was after B

Possible Sequences:

B, D, A, E, C

B, A, D, E, C

B, A, E, D, C

B, A, E, C, D


Direction of ForceDirection of Force• Small projectiles entry-Small projectiles entry-

exitexit• Entry: smaller hole, Entry: smaller hole,

smooth surfacesmooth surface• Exit: wider hole, crater Exit: wider hole, crater

shape, rough surfaceshape, rough surface

• Radial fractures Radial fractures indicate direction of indicate direction of forceforce

• 3R3R Rule: Rule: • RRadial fractureadial fracture• RRight angleight angle• RReverse side of forceeverse side of force

Entry Hole

Exit Hole

cratering

Right Angle side

Force came from this side


Class Characteristic of GlassClass Characteristic of Glass• Class characteristics of glass are limited because Class characteristics of glass are limited because

glass is so inert—difficult to dissolve in solventsglass is so inert—difficult to dissolve in solvents• Exception is the Inductively Coupled Plasma Mass Exception is the Inductively Coupled Plasma Mass

Spectrometer (ICP/MS)—digests glass and performs Spectrometer (ICP/MS)—digests glass and performs elemental analysis to determine chemical elemental analysis to determine chemical compositioncomposition

• ICP/MS in few crime labsICP/MS in few crime labs• Most labs can analyze class characteristics: Most labs can analyze class characteristics:

• Physical appearance – size, shape, thicknessPhysical appearance – size, shape, thickness• ColorColor• DensityDensity• Refractive indexRefractive index


Refractive IndexRefractive Index• Refractive Index (RI) is the ratio of the Refractive Index (RI) is the ratio of the

velocity of light in a vacuum to it’s velocity velocity of light in a vacuum to it’s velocity in a mediumin a medium

• Equation: Equation: RI = velocity of light in vacuum/velocity of light in mediumRI = velocity of light in vacuum/velocity of light in medium

• As light passes from one medium to As light passes from one medium to another, it slows down, causing it to bend another, it slows down, causing it to bend or refractor refract

The straw appears bent due to refraction of light


Glass Identification Using Glass Identification Using Properties of RefractionProperties of Refraction

• If two transparent If two transparent materials have the materials have the same RI, light will not same RI, light will not refract as it passes refract as it passes from one to the other. from one to the other.

• If solid is placed in If solid is placed in liquid with same RI, it liquid with same RI, it will disappear.will disappear.

Solid is visible in air.

Solid has same RI as liquid. Starts to disappear.

Solid immersed in liquid. Not visible.


Glass Identification UsingGlass Identification UsingProperties of RefractionProperties of Refraction

• If transparent material is If transparent material is heated, its refractive index heated, its refractive index will decreasewill decrease

• Amount of refraction light Amount of refraction light undergoes depends on undergoes depends on wavelength. Longer the wavelength. Longer the wavelength, less refraction wavelength, less refraction it undergoesit undergoes

• If a transparent solid is If a transparent solid is immersed in a transparent immersed in a transparent liquid of different refractive liquid of different refractive index, bright halo is seen index, bright halo is seen around solid—the around solid—the Becke Becke lineline..

• If transparent solid is If transparent solid is immersed in transparent immersed in transparent liquid of different refractive liquid of different refractive index and put under index and put under microscope, Becke line will microscope, Becke line will move as ocular to objective move as ocular to objective lens distance is increasedlens distance is increased


Becke LinesBecke LinesBecke Lines

Glass immersedin liquid of LOWER index of refraction

Becke line

Glass immersedin liquid of HIGHER index of refraction

Becke line

Movement of Becke lines as the objective to stage distance of microscope is increased

Glass fragment under microscope

1717

Refractive Index Determination Refractive Index Determination of a Small Glass Fragmentof a Small Glass Fragment

• Refractive index of small pieces of glass can be Refractive index of small pieces of glass can be determined using commercially available liquids determined using commercially available liquids whose refractive indexes are knownwhose refractive indexes are known

A B CPhoto A shows a small piece of Pyrex glass not immersed in a liquid.

Photo B shows the same piece of glass immersed in water.

Photo C shows the piece immersed in vegetable oil. Pyrex and vegetable oil have similar indices of refraction as shown by the disappearance of the glass in the oil.


Refractive Index Determination Refractive Index Determination of a Small Glass Fragmentof a Small Glass Fragment

• Crime labs also use a hot stage Crime labs also use a hot stage microscope that allows determination of microscope that allows determination of refractive indexrefractive index

• Use liquid with slightly higher Use liquid with slightly higher

RI than the glassRI than the glass• As liquid heats, RI decreasesAs liquid heats, RI decreases• When glass disappears, When glass disappears,

the RI is determinedthe RI is determined

Hot Stage Microscope


SoilSoil

• Found almost anywhere outdoorsFound almost anywhere outdoors• Consists of crushed rocks and minerals Consists of crushed rocks and minerals

mixed with decayed plant and animal mixed with decayed plant and animal material (humus)material (humus)

• Difficult to categorize—takes a good deal Difficult to categorize—takes a good deal of skill to identify its componentsof skill to identify its components

• Most forensic science labs do not analyze Most forensic science labs do not analyze soil evidence except to the extent soil evidence except to the extent someone has left an impression in the soilsomeone has left an impression in the soil—casting for identification of footwear—casting for identification of footwear


Difficulty In Using Soil As Difficulty In Using Soil As EvidenceEvidence

• Soil varies in chemical and physical Soil varies in chemical and physical properties from place to placeproperties from place to place

• No forensic classification scheme for soilsNo forensic classification scheme for soils• Takes good deal of skill to characterize Takes good deal of skill to characterize

minerals in soilminerals in soil• Soil is always Soil is always class evidenceclass evidence and has no and has no

unique qualities that allow for its unique qualities that allow for its individualizationindividualization


Color Analysis and Color Analysis and Humic Fractions of SoilsHumic Fractions of Soils

• Soils may be characterized Soils may be characterized by their colorby their color

• Color is due to its mineral Color is due to its mineral and moisture contentand moisture content

• Some laboratories use Some laboratories use HPLC to separate and HPLC to separate and display humus display humus components of soils by components of soils by extracting soil with extracting soil with acetonitrile and filtering itacetonitrile and filtering it

Liquid Chromatogram of a Soil Sample

Chapter 19 glass soil_new design

Science

Transcript of Chapter 19 glass soil_new design