Forensic Science: Forensic Science: An IntroductionAn Introduction

Unit A: Crime Scene ProcessingUnit A: Crime Scene Processing

DefinitionsDefinitions

Forensic Science - the application of the Forensic Science - the application of the knowledge and technology of science to knowledge and technology of science to the criminal and civil laws that are the criminal and civil laws that are enforced by police agencies in a criminal enforced by police agencies in a criminal justice system.justice system.

Locard’s Exchange Principle – when two Locard’s Exchange Principle – when two objects come in contact with each other, a objects come in contact with each other, a cross-transfer of materials occur. This cross-transfer of materials occur. This allows us to connect criminals to crime allows us to connect criminals to crime scenes.scenes.

The American Academy of The American Academy of Forensic Science DepartmentsForensic Science Departments

Criminalistics - crime scene processingCriminalistics - crime scene processing Engineering Science - reconstructionEngineering Science - reconstruction GeneralGeneral Jurisprudence - legalJurisprudence - legal Odontology - bitemarksOdontology - bitemarks Pathology/Biology – autopsy, DNAPathology/Biology – autopsy, DNA Physical Anthropology – skeletal remainsPhysical Anthropology – skeletal remains Psychiatry and Behavioral SciencePsychiatry and Behavioral Science Questioned DocumentsQuestioned Documents Toxicology – drugs and poisonsToxicology – drugs and poisons

Additional disciplinesAdditional disciplines

Fingerprint examinationFingerprint examinationFirearm and toolmark examinationFirearm and toolmark examinationComputer and digital analysisComputer and digital analysisPhotography Photography Entomology - insectsEntomology - insects

Historical EventsHistorical Events

Late 1700s - Arsenic and ToxicologyLate 1700s - Arsenic and ToxicologyMid 1800s – MicroscopyMid 1800s – MicroscopyLate 1800s – Identification (Bertillion) Late 1800s – Identification (Bertillion) Early 1900s – Fingerprinting, Blood and Early 1900s – Fingerprinting, Blood and

Serology, Document Examination, Serology, Document Examination, MicroscopyMicroscopy

Mid 1900s – Chromatography, Mid 1900s – Chromatography, Spectrophotometry, Electrophoresis, DNASpectrophotometry, Electrophoresis, DNA

PublicationsPublications

Yi Yu Ji “A Collection of Criminal Cases”Yi Yu Ji “A Collection of Criminal Cases” ““A Treatise on Forensic Medicine and Public A Treatise on Forensic Medicine and Public

Health” (Fodere, 1798)Health” (Fodere, 1798) ““Finger Prints” (Galton, 1892)Finger Prints” (Galton, 1892) ““Criminal Investigation” (Gross, 1893)Criminal Investigation” (Gross, 1893) Sherlock Holmes –fiction (Doyle 1880s)Sherlock Holmes –fiction (Doyle 1880s) ““Treaty of Criminalistics (Locard, 1931)Treaty of Criminalistics (Locard, 1931) Hypervariable Minisatellite Regions in Human Hypervariable Minisatellite Regions in Human

DNA (Jeffreys, 1985)DNA (Jeffreys, 1985)

Crime LabsCrime Labs LocardLocard Los Angeles - oldestLos Angeles - oldest FBIFBI DEADEA ATFATF US Postal ServiceUS Postal Service SBISBI State system State system LocalLocal Delocalized labs – no common managementDelocalized labs – no common management

Crime Lab ServicesCrime Lab Services

Basic ServicesBasic ServicesPhotography Photography Physical Science Physical Science Biology/DNABiology/DNAFirearmsFirearmsDocument Document

ExaminationExamination

Optional ServicesOptional Services ToxicologyToxicology Latent FingerprintLatent Fingerprint PolygraphyPolygraphy Voice AnalysisVoice Analysis Forensic PsychiatryForensic Psychiatry Forensic OdontologyForensic Odontology Forensic EngineeringForensic Engineering Forensic Computer and Forensic Computer and

Digital AnalysisDigital Analysis

What Forensic Scientists DoWhat Forensic Scientists Do

Analyze physical evidenceAnalyze physical evidenceUse scientific methodsUse scientific methods

Determine admissibility of evidenceDetermine admissibility of evidenceFrye v US (1923) – general acceptanceFrye v US (1923) – general acceptance

Judge scientific evidenceJudge scientific evidenceDaubert case (1993) – trial judge is gatekeeperDaubert case (1993) – trial judge is gatekeeper

Provide expert testimonyProvide expert testimonyFurnish trainingFurnish training

Forensic ScienceForensic Science

Forensic scientist seek to reach truth Forensic scientist seek to reach truth based on available evidence. The legal based on available evidence. The legal process does not, however, always seek process does not, however, always seek truth but follow process.truth but follow process.

Reliable methods possess characteristics Reliable methods possess characteristics of:of: IntegrityIntegrityCompetenceCompetenceDefensible techniqueDefensible techniqueRelevant experienceRelevant experience

Reliable MethodsReliable Methods

Help distinguish evidence from Help distinguish evidence from coincidencecoincidence

Allow alternative results to be ranked by Allow alternative results to be ranked by basic scientific principlesbasic scientific principles

Allow tests to either prove or disprove Allow tests to either prove or disprove alternative hypothesesalternative hypotheses

Pursue testing by breaking hypotheses Pursue testing by breaking hypotheses into their smallest logical componentsinto their smallest logical components

Physical EvidencePhysical Evidence

Anything physical objects that can link a Anything physical objects that can link a crime to its victims or to suspects.crime to its victims or to suspects.

Has to be collected from crime sceneHas to be collected from crime sceneMust be relevant to the crime Must be relevant to the crime Requires the collector to understand what Requires the collector to understand what

the capabilities and limitations of the crime the capabilities and limitations of the crime lab arelab are

Physical EvidencePhysical Evidence

Crime labs do not solve crimes, only add Crime labs do not solve crimes, only add evidence to help police investigation link evidence to help police investigation link the suspect to the crime.the suspect to the crime.

The forensic scientists must know how to The forensic scientists must know how to collect and preserve evidence found at the collect and preserve evidence found at the crime scenecrime scene

Ways to classify a crime sceneWays to classify a crime scene

Primary vs secondary crime scenePrimary vs secondary crime sceneMacroscopic vs microscopic scenesMacroscopic vs microscopic scenesType of crimeType of crimeLocation of crimeLocation of crime

Use of Physical Evidence Use of Physical Evidence

Information on evidence of a crime Information on evidence of a crime (Corpus Delecti)(Corpus Delecti)

Information on the criminal (Modus Information on the criminal (Modus Operandi)Operandi)

Linkage on persons, scenes and objectsLinkage on persons, scenes and objects Identification of suspectsIdentification of suspects Identification of unknown substancesIdentification of unknown substancesReconstruction of a crimeReconstruction of a crimeProviding investigative leadsProviding investigative leads

Arriving at the Crime SceneArriving at the Crime Scene

Secure and isolate the crime sceneSecure and isolate the crime sceneDetermine boundaries of crime scene and Determine boundaries of crime scene and

priorities for evidence collectionpriorities for evidence collectionRough sketch Rough sketch Finished sketchFinished sketchPhotograph Photograph Videotaping Videotaping NotesNotes

Collecting EvidenceCollecting Evidence

Conduct a systematic search for evidence; Conduct a systematic search for evidence; be unabiased and thorough.be unabiased and thorough.

Field techniciansField techniciansWhat to look for depends on the crime and What to look for depends on the crime and

what specific locations of the crime scene what specific locations of the crime scene would most likely be affectedwould most likely be affected

Microscopic or massive objectsMicroscopic or massive objectsCollect carriers of possible evidenceCollect carriers of possible evidenceVacuum or sweeping collectedVacuum or sweeping collected

Packaging of EvidencePackaging of Evidence

Prevent any changes from occurring Prevent any changes from occurring (contamination, breakage, evaporation, (contamination, breakage, evaporation, bending, loss)bending, loss)

Process trace evidence from original Process trace evidence from original object (shirt, shoe) rather than isolating object (shirt, shoe) rather than isolating and packaging if possibleand packaging if possible

Package evidence separatelyPackage evidence separately

Tools for Collecting EvidenceTools for Collecting Evidence

ForcepsForcepsEvidence envelopes and pill bottlesEvidence envelopes and pill bottlesSwabsSwabsSpecial concerns (mold, evaporation)Special concerns (mold, evaporation)Various light sourcesVarious light sourcesLatent fingerprintsLatent fingerprintsMobile crime labs or better yet crime Mobile crime labs or better yet crime

scene search vehicle scene search vehicle

Chain of custodyChain of custody

Continuity of possession; every person Continuity of possession; every person who touched it must be accounted forwho touched it must be accounted for

Standards for collecting, labeling, and Standards for collecting, labeling, and submitting evidence forms are necessary submitting evidence forms are necessary for court for court

Labels include collectors initials, location Labels include collectors initials, location of evidence, date of collection. of evidence, date of collection. Identification numbers must also be usedIdentification numbers must also be used

Submission of EvidenceSubmission of Evidence

Standard/reference samplesStandard/reference samplesSubstance controlsSubstance controlsEvidence submission form will detail the Evidence submission form will detail the

evidence collect and particular type of evidence collect and particular type of examination/analysis requested. examination/analysis requested.

Lab tech not bound by requestsLab tech not bound by requests

Common Types of EvidenceCommon Types of Evidence Common Types of EvidenceCommon Types of Evidence Blood, semen, and salivaBlood, semen, and saliva DocumentsDocuments DrugsDrugs FibersFibers FingerprintsFingerprints Firearms and ammunitionFirearms and ammunition GlassGlass HairHair ImpressionsImpressions Organs and physiological Organs and physiological

fluidsfluids

PaintPaint Petroleum productsPetroleum products Plastic bagsPlastic bags Plastic, rubber, and other Plastic, rubber, and other

polymerspolymers Powder residuesPowder residues Serial numbersSerial numbers Soil and mineralsSoil and minerals Tool marksTool marks Vehicle lightsVehicle lights Wood and other Wood and other

vegetative mattervegetative matter

Examination of Physical EvidenceExamination of Physical Evidence

IdentificationIdentification Determining the identity of a substance with a near Determining the identity of a substance with a near

absolute certainty while ruling out other substancesabsolute certainty while ruling out other substances

ComparisonComparison Comparing the evidence to one or more selected Comparing the evidence to one or more selected

references and drawing a conclusion about its origins.references and drawing a conclusion about its origins. Individual characteristics –properties of evidence that Individual characteristics –properties of evidence that

can be attributed to a common source with extremely can be attributed to a common source with extremely high certainty. (eg. fingerprints, DNA, bullets)high certainty. (eg. fingerprints, DNA, bullets)

Class characteristics – properties of evidence that can Class characteristics – properties of evidence that can be associated with a group and never with a single be associated with a group and never with a single source. ( eg. Blood type, tire marks)source. ( eg. Blood type, tire marks)

Significance of Physical EvidenceSignificance of Physical Evidence

Assessing the values of evidenceAssessing the values of evidence Class characteristics of evidence is valuable in Class characteristics of evidence is valuable in

corroborating events.corroborating events. Multiple class evidence can lead to a high level of Multiple class evidence can lead to a high level of

certainty of origincertainty of origin

Cautions and limitations of evidenceCautions and limitations of evidence A person can be exonerated or excluded from A person can be exonerated or excluded from

suspicion if evidence collected from the crime suspicion if evidence collected from the crime scene is different from the reference samples scene is different from the reference samples collected from the person.collected from the person.

Forensic DatabasesForensic Databases

One-on-one comparison requires a suspectOne-on-one comparison requires a suspect Computerized databases help link evidence to Computerized databases help link evidence to

peoplepeople Fingerprint databases – IAFISFingerprint databases – IAFIS DNA database – CoDISDNA database – CoDIS Ballistics database – IBISBallistics database – IBIS Automative Paint database – PDQAutomative Paint database – PDQ Shoeprint database - SICaRShoeprint database - SICaR

Crime-Scene ReconstructionCrime-Scene Reconstruction

The method used to support a likely The method used to support a likely sequence of events at a crime scene by sequence of events at a crime scene by observing and evaluating physical observing and evaluating physical evidence and statements made by those evidence and statements made by those involved with the incidentinvolved with the incident

Combined efforts of MEs, CSI, and law Combined efforts of MEs, CSI, and law enforcement personnelenforcement personnel

Examples: was body moved, bullet Examples: was body moved, bullet trajectory, blood splattertrajectory, blood splatter

HistoryHistory

Alphonse Bertillion (1883) – anthropometryAlphonse Bertillion (1883) – anthropometry Henry Fauld (1880) - first published on possible Henry Fauld (1880) - first published on possible

use of fingerprintsuse of fingerprints Francis Galton (1892) – published Francis Galton (1892) – published Finger PrintsFinger Prints

described types of printsdescribed types of prints Sir Edward Henry (1897) – classification system Sir Edward Henry (1897) – classification system

used todayused today FBI (1924) – new formed FBI held world’s FBI (1924) – new formed FBI held world’s

largest fingerprint databaselargest fingerprint database

Fingerprint PrinciplesFingerprint Principles 1. A fingerprint is an individual characteristic; no two 1. A fingerprint is an individual characteristic; no two

fingerprints have been found to possess identical ridge fingerprints have been found to possess identical ridge characteristicscharacteristics No minimum number of comparisons to establish identityNo minimum number of comparisons to establish identity

2. A fingerprint remains unchanged during an individual’s 2. A fingerprint remains unchanged during an individual’s lifetimelifetime Friction ridges and grooves created by dermal papillaeFriction ridges and grooves created by dermal papillae Sweat glands on the ridges deposit perspiration and oilsSweat glands on the ridges deposit perspiration and oils Latent fingerprint – left by deposits and is invisible to the naked Latent fingerprint – left by deposits and is invisible to the naked

eyeeye 3. Fingerprints have general ridge patterns that permit 3. Fingerprints have general ridge patterns that permit

them to be systematically classified.them to be systematically classified.

Categories of FingerprintsCategories of Fingerprints

Loop – ridge lines enter one side of Loop – ridge lines enter one side of pattern and curve around to exit from the pattern and curve around to exit from the same side of pattern. (65%)same side of pattern. (65%)Ulnar loop – opens toward little fingerUlnar loop – opens toward little fingerRadial loop – opens toward thumbRadial loop – opens toward thumb

Ulnar Loop Radial Loop

Categories of FingerprintsCategories of Fingerprints

Whorl – ridge lines rounded or circular and Whorl – ridge lines rounded or circular and have two deltas(30-35%)have two deltas(30-35%)Plain whorlPlain whorl

Central pocket loopCentral pocket loop

Double loopDouble loop

Accidental loopAccidental loop

Categories of FingerprintsCategories of Fingerprints

Arch – ridge lines enter print from one side Arch – ridge lines enter print from one side and exit from the other (5%)and exit from the other (5%)PlainPlain

TentedTented

Classification of FingerprintsClassification of Fingerprints

Henry systemHenry system – numerical system involving the – numerical system involving the presence or absence of the whorl pattern on presence or absence of the whorl pattern on each finger as part of the primary classification..each finger as part of the primary classification.. This does not identify someone, only reduce the This does not identify someone, only reduce the

number of possible candidatesnumber of possible candidates

AFISAFIS – 10 print system that can search 500,000 – 10 print system that can search 500,000 stored ten-prints in 0.8 secondsstored ten-prints in 0.8 seconds Data entered now by Livescan rather than ink rolling.Data entered now by Livescan rather than ink rolling. Human decisions must still be madeHuman decisions must still be made Software incompatibilities among statesSoftware incompatibilities among states

Methods of DetectionMethods of Detection

Types of printsTypes of printsLatent printLatent printVisible print – deposited ink, blood, dirtVisible print – deposited ink, blood, dirtPlastic print – impression in a soft surfacePlastic print – impression in a soft surface

Locating prints – RUVISLocating prints – RUVIS

Developing PrintsDeveloping PrintsPowdersPowders

CharcoalCharcoalMagneticMagneticFluorescent Fluorescent

ChemicalsChemicals Iodine fuming (sublimation) Iodine fuming (sublimation) NinhydrinNinhydrinPhysical developer (silver nitrate) Physical developer (silver nitrate) Super Glue fuming Super Glue fuming Alternate Light Sources/ LEDAlternate Light Sources/ LED

Preservation of Developed Preservation of Developed PrintsPrints

PhotographsPhotographsPrint surface should be removed in its Print surface should be removed in its

entirety (covered with cellophane)entirety (covered with cellophane)Lifted from surface with tapeLifted from surface with tapeDigital imaging into pixels – allows Digital imaging into pixels – allows

adjustments to be made to enhance adjustments to be made to enhance picturepicture