Forensic Science:Forensic Science:An IntroductionAn Introduction

Trace EvidenceTrace Evidence

Properties of MatterProperties of Matter

Physical properties – describe the Physical properties – describe the behavior of matter; can change behavior of matter; can change without changing the composition of without changing the composition of the matter (melting, solubility)the matter (melting, solubility)

Chemical properties – describes the Chemical properties – describes the behavior of matter in relation to behavior of matter in relation to other substances; if this property other substances; if this property changes, then the substance has changes, then the substance has changed (gas production, changed (gas production, precipitation, reactivity)precipitation, reactivity)

Metric SystemMetric System

Metric conversionMetric conversion

English/Standard to Metric English/Standard to Metric ConversionsConversions

Nature of MatterNature of Matter

Matter – anything that has mass and Matter – anything that has mass and takes up spacetakes up space

Element – simplest form of matter that Element – simplest form of matter that cannot be broken down further by cannot be broken down further by chemical means. (Periodic Table)chemical means. (Periodic Table)

Atom – smallest unit of an element that Atom – smallest unit of an element that still retains the properties of that still retains the properties of that elementelement

Compound – a pure substance made up Compound – a pure substance made up of two or more elements bound togetherof two or more elements bound together

States of MatterStates of Matter

Solids – molecules of matter held Solids – molecules of matter held very closely together; has definite very closely together; has definite shape and volumeshape and volume

Liquid – molecules of matter held Liquid – molecules of matter held more loosely together by attractive more loosely together by attractive forces; has definite volume but shape forces; has definite volume but shape depends on containerdepends on container

Gas – molecules of matter are Gas – molecules of matter are allowed to freely move; has not allowed to freely move; has not definite volume or shapedefinite volume or shape

Changes in the States of MatterChanges in the States of Matter

FreezingFreezing MeltingMelting CondensationCondensation SublimationSublimation EvaporationEvaporation BoilingBoiling

Phase – a Phase – a separation of separation of different different substances of substances of matter due to matter due to visible boundaries visible boundaries between thembetween them

Light as a WaveLight as a Wave

Wavelength – distance from crest to Wavelength – distance from crest to crestcrest

Frequency – number of waves that Frequency – number of waves that pass a given pointpass a given point

Amplitude – how high the waves areAmplitude – how high the waves are Speed of light – wavelength x Speed of light – wavelength x

frequencyfrequency

Light as a WaveLight as a Wave

Dispersion – the separating light into Dispersion – the separating light into its different component colorsits different component colors

Refraction - the bending of light Refraction - the bending of light caused by a change in its velocitycaused by a change in its velocity

Reflection – the bouncing of light off Reflection – the bouncing of light off a surfacea surface

Transmission – the passing of light Transmission – the passing of light through a substancethrough a substance

Absorption – the Absorption – the

Electromagnetic SpectrumElectromagnetic Spectrum

Light as a ParticleLight as a Particle

Photon – a discrete packet or particle Photon – a discrete packet or particle of electromagnetic radiationof electromagnetic radiation

Each as a certain amount of energy Each as a certain amount of energy related to its frequency such that related to its frequency such that

E = hf h is Planck’s constantE = hf h is Planck’s constant

f is frequencyf is frequency

Physical Properties of MatterPhysical Properties of Matter

Temperature – measure of heat intensity; Temperature – measure of heat intensity; average amount of molecular movement average amount of molecular movement in a substance (Fahrenheit and Celsius)in a substance (Fahrenheit and Celsius)

Weight – the force of gravity exerted on a Weight – the force of gravity exerted on a substance; differs in the universe w = mgsubstance; differs in the universe w = mg

Mass – amount of matter an object has; a Mass – amount of matter an object has; a constantconstant

Density – mass of an object in relation to Density – mass of an object in relation to its volume; it remains the same regardless its volume; it remains the same regardless of the size of an object (intensive of the size of an object (intensive property)property)

Physical Properties of MatterPhysical Properties of Matter

Refractive Index – the ratio of the Refractive Index – the ratio of the speed of light in a vacuum to its speed of light in a vacuum to its speed of light in a given mediumspeed of light in a given medium RI = RI = velocity of light in vacuumvelocity of light in vacuum velocity of light in mediumvelocity of light in medium Refractive index of water is 1.333 thus it Refractive index of water is 1.333 thus it

travels 1.333 times as fast in a vacuum travels 1.333 times as fast in a vacuum as it does in wateras it does in water

Crystalline solids may have two Crystalline solids may have two refractive indeces (birefringence) while refractive indeces (birefringence) while amorphous solids do not.amorphous solids do not.

Forensic Analysis of GlassForensic Analysis of Glass

Composition – amorphous solid of Composition – amorphous solid of silicon mixed with other metal oxidessilicon mixed with other metal oxides Soda-lime glass – windows and bottlesSoda-lime glass – windows and bottles Sodium, calcium, magnesium, aluminum Sodium, calcium, magnesium, aluminum

are common metal oxides added are common metal oxides added Borosilicates – boron is added to make Borosilicates – boron is added to make

heat-resistance (headlights, Pyrex)heat-resistance (headlights, Pyrex) Tempered – strengthened by heat/cool Tempered – strengthened by heat/cool

stress during manufacturing (car side stress during manufacturing (car side windows)windows)

Laminated – two sheets of glass with Laminated – two sheets of glass with plastic sheet in between (windshields)plastic sheet in between (windshields)

Forensic Glass AnalysisForensic Glass Analysis

Comparing fragments Comparing fragments Flotation Flotation Refractive index comparisonRefractive index comparison Classification of glass samplesClassification of glass samples Glass fracturesGlass fractures

Concentric fractureConcentric fracture Radial fractureRadial fracture 3R rule: Radial fractures form Right angles on 3R rule: Radial fractures form Right angles on

the Reverse side of the forcethe Reverse side of the force Collection and preservation of glass Collection and preservation of glass

evidenceevidence

Trace EvidenceTrace Evidence

transferred between individuals and transferred between individuals and objects during the commission of a objects during the commission of a crimecrime

Often can corroborate other evidence Often can corroborate other evidence Generally class characteristics and Generally class characteristics and

not individual characteristicsnot individual characteristics Examples: Hair, Fibers, Metals, Examples: Hair, Fibers, Metals,

Paints, Soil, Glass, and ImpressionsPaints, Soil, Glass, and Impressions

Hair MorphologyHair Morphology

Hair follicle, Shaft, Tip endHair follicle, Shaft, Tip end Cuticle – outer layer, keratinized Cuticle – outer layer, keratinized

scale structure, animal specificscale structure, animal specific Cortex – main body of hair shaft, Cortex – main body of hair shaft,

colorcolor Medulla – center; cellular column, Medulla – center; cellular column,

medullary indexmedullary index

Hair GrowthHair Growth

Root is where the hair growsRoot is where the hair grows Anagen phase – initial growth phase, lasts Anagen phase – initial growth phase, lasts

up to six yrs, root attached to follicle, up to six yrs, root attached to follicle, provides follicular tag; grows 1 cm per provides follicular tag; grows 1 cm per monthmonth

Catagen phase – decreasing growth rate, Catagen phase – decreasing growth rate, 2-3 wks, 2-3 wks,

Telogen phase – growth stops, 2-6 months, Telogen phase – growth stops, 2-6 months, hair is shedhair is shed

Forensics of HairForensics of Hair

Identification of animal hairIdentification of animal hair Comparison of human hairsComparison of human hairs Color, length, diameter, medulla structure, Color, length, diameter, medulla structure,

cortex pigmentscortex pigments Microscopic examination is presumptive Microscopic examination is presumptive

while DNA is confirmativewhile DNA is confirmative Standard/reference samplesStandard/reference samples

50 full length head hairs50 full length head hairs 24 full length public hairs24 full length public hairs

From hair, can we learn about…From hair, can we learn about…

Body area origin? yesBody area origin? yes Racial origin? yesRacial origin? yes Age or sex? NoAge or sex? No Forcibly removed? YesForcibly removed? Yes Individualize human hair? Yes, Individualize human hair? Yes,

through DNAthrough DNA

FibersFibers

Natural fibers from animal or plant Natural fibers from animal or plant sources, cottonsources, cotton

Manufactured fibers from natural or Manufactured fibers from natural or synthetic polymerssynthetic polymers

Types of FibersTypes of Fibers

AcetateAcetate AcrylicAcrylic AramidAramid BicomponentBicomponent LyocellLyocell MelamineMelamine ModacrylicModacrylic

NylonNylon OlefinOlefin PolyesterPolyester PBIPBI RayonRayon SpandexSpandex

Forensics of FibersForensics of Fibers

Microscopic examination of fibersMicroscopic examination of fibers

Color, diameter, striation, pittingColor, diameter, striation, pitting MicrospectrophotometryMicrospectrophotometry Chemical compositionChemical composition BirefringerenceBirefringerence Infrared absorptionInfrared absorption

MetalsMetals

Trace elements of less than 1% Trace elements of less than 1% composition may provide invisible composition may provide invisible markers to help in comparisonsmarkers to help in comparisons

Composition of PaintComposition of Paint

Electrocoat primerElectrocoat primer Primer surfacerPrimer surfacer BasecoatBasecoat ClearcoatClearcoat

Forensics of PaintForensics of Paint

MicroscopicMicroscopic Pyrolysis gas chromatographyPyrolysis gas chromatography Infrared spectrophotometryInfrared spectrophotometry Emission spectrophotometryEmission spectrophotometry Paint Data Query (PDQ)Paint Data Query (PDQ)

SoilSoil

Examination of soil content include natural Examination of soil content include natural and manufactured objects in it.and manufactured objects in it.

Microscopic examination can identify Microscopic examination can identify minerals by color, shape, refractive index, minerals by color, shape, refractive index, or birefringenceor birefringence

Density-gradient tubes determine the Density-gradient tubes determine the density distribution of soildensity distribution of soil

Spectrophotometry determines soil Spectrophotometry determines soil settlingsettling

Bullet and Cartridge ComparisonsBullet and Cartridge Comparisons

Gum barrel has grooves (rifling) to Gum barrel has grooves (rifling) to help spin the bullethelp spin the bullet

The diameter of the bore of the The diameter of the bore of the barrel is called the caliberbarrel is called the caliber

Various processes of creating rifling Various processes of creating rifling can be used to identify maker of guncan be used to identify maker of gun

Various processes of creating rifling Various processes of creating rifling all create striations that are unique all create striations that are unique to gunto gun

Bullet and Cartridge ComparisonsBullet and Cartridge Comparisons The striation markings on the bullet can The striation markings on the bullet can

provide individual characteristics for gun provide individual characteristics for gun comparison.comparison.

FBI maintains a record known as the General FBI maintains a record known as the General Rifling Characteristics File which lists class Rifling Characteristics File which lists class characteristics for known weapons.characteristics for known weapons.

Shotguns do not have rifling thus no Shotguns do not have rifling thus no striations. The size of the shotgun is referred striations. The size of the shotgun is referred to as its gauge.to as its gauge.

Cartridge casings also will have markings on it Cartridge casings also will have markings on it from the loading, firing or ejection from the loading, firing or ejection mechanisms.mechanisms.

Automated Firearms Search Automated Firearms Search SystemsSystems

DRUGFIRE developed by the FBI DRUGFIRE developed by the FBI focused on the casingsfocused on the casings

IBIS developed by the ATF focused IBIS developed by the ATF focused more on the bulletsmore on the bullets

NIBIN incorporates both systemsNIBIN incorporates both systems Ballistic Fingerprinting of guns prior Ballistic Fingerprinting of guns prior

to sale is being discussed.to sale is being discussed.

Gunpowder ResiduesGunpowder Residues Incomplete combusted gun powder residue Incomplete combusted gun powder residue

deposited on target allows for distance deposited on target allows for distance determinationdetermination

Without the weapon, generalizations can be Without the weapon, generalizations can be made about the distancemade about the distance Melted clothing fibers and star shape hole – Melted clothing fibers and star shape hole –

less than 1 inch awayless than 1 inch away black smoke around hole – 12-18 inches awayblack smoke around hole – 12-18 inches away scattered specks around hole – 25 inches awayscattered specks around hole – 25 inches away only bullet wipe – greater 3 feet awayonly bullet wipe – greater 3 feet away

Shotgun distances can be determined by the Shotgun distances can be determined by the scatter of the pellets (1 inch scatter for scatter of the pellets (1 inch scatter for

every yard of distance)every yard of distance) Gunpowder residues can be developed Gunpowder residues can be developed on clothing using chemical testson clothing using chemical tests

Gun Shot ResidueGun Shot Residue

Primer residue is propelled backward Primer residue is propelled backward and deposited on the hand of the and deposited on the hand of the shootershooter

GSR can be detected chemically or GSR can be detected chemically or microscopically (SEM) microscopically (SEM)

BallisticsBallistics

A bullet encounters four ballistic A bullet encounters four ballistic regimensregimens

Internal ballistics – primer and propellentsInternal ballistics – primer and propellents Internal ballistics – movement throught Internal ballistics – movement throught

the barrel; grooves and lands the barrel; grooves and lands External ballistics – gravity, Coriolis External ballistics – gravity, Coriolis

effect, aerodynamic, Magnus force, yaw, effect, aerodynamic, Magnus force, yaw, ballistic coefficientballistic coefficient

Terminal ballistics – hitting the target; Terminal ballistics – hitting the target; yaw, lacerations, crushing, cavitationyaw, lacerations, crushing, cavitation

Terminal ballisticsTerminal ballistics

ToolmarksToolmarks Any impression, cut, gouge or abrasion Any impression, cut, gouge or abrasion

caused by a tool coming into contact with caused by a tool coming into contact with another object.another object.

Typically, impression comes from prying Typically, impression comes from prying action of toolaction of tool

Damage, wear patterns as well as Damage, wear patterns as well as manufactured striations may be left in manufactured striations may be left in impressionimpression

Silicone casting material is used to create Silicone casting material is used to create a cast of the impression for comparison a cast of the impression for comparison with the suspected tool.with the suspected tool.

The impression may also contain trace The impression may also contain trace evidence such as paint from the tool.evidence such as paint from the tool.

Other ImpressionsOther Impressions Shoe printShoe print Tire printsTire prints Fabric impressionsFabric impressions Impression must be photographed, lifted or Impression must be photographed, lifted or

casted, and then comparedcasted, and then compared Shoe and tire marks in soft earth can be Shoe and tire marks in soft earth can be

castedcasted Bitemarks can be casted Bitemarks can be casted Dust left on a floor can be lifted Dust left on a floor can be lifted

electrostaticallyelectrostatically Bloody footwear impression can be Bloody footwear impression can be

enhanced with chemical treatment.enhanced with chemical treatment.

Document ExaminationDocument Examination

Questioned document – any Questioned document – any document which some issue has document which some issue has been raised or that is the subject of been raised or that is the subject of an investigation. an investigation.

Requires knowledge in microscopy, Requires knowledge in microscopy, photography, and chromatography photography, and chromatography

Handwriting ComparisonsHandwriting Comparisons General styleGeneral style Variations in handwritingVariations in handwriting

Angle, slope, speed, pressure, spacing, Angle, slope, speed, pressure, spacing, dimension, connections, pen movement, dimension, connections, pen movement, writing skill, finger dexterity, margins, spacing, writing skill, finger dexterity, margins, spacing, alignment, phraseology, spelling, grammaralignment, phraseology, spelling, grammar

Exemplars – an authentic sample for Exemplars – an authentic sample for comparison purposes, such as handwritingcomparison purposes, such as handwriting

Natural variations – normal deviations Natural variations – normal deviations found between repeated specimens of an found between repeated specimens of an individual’s handwritingindividual’s handwriting

Typescript ComparisonsTypescript Comparisons

Photocopier – random debris on the Photocopier – random debris on the glass cover or machinery can be glass cover or machinery can be reproducedreproduced

Fax machines – transmitting terminal Fax machines – transmitting terminal identifier (TTI) font can be alteredidentifier (TTI) font can be altered

Computer printers – letter shape and Computer printers – letter shape and toners may varytoners may vary

Typewriters – type face alignment Typewriters – type face alignment will varywill vary

Alterations in DocumentsAlterations in Documents Erasure – removal of writing or printing Erasure – removal of writing or printing

from a document normally accomplished from a document normally accomplished by either chemical or abrasive meansby either chemical or abrasive means

Obliterations – blotting out or smearing Obliterations – blotting out or smearing over writing to make it unreadableover writing to make it unreadable

Charred document – darkened and brittle Charred document – darkened and brittle by exposure to fire or heatby exposure to fire or heat

Indented Writings – impressions left on Indented Writings – impressions left on paper positioned under a piece of paper paper positioned under a piece of paper that has been written onthat has been written on

Ink and paper ComparisonsInk and paper Comparisons

Chromatography and ink tags allow Chromatography and ink tags allow comparison of inkcomparison of ink

Cellulose content, weight, color, Cellulose content, weight, color, watermarks, and additives vary in watermarks, and additives vary in paperpaper