Types of Physical Types of Physical EvidenceEvidence

Chapter 3 NotesChapter 3 Notes

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I CAN Skills for the Physical I CAN Skills for the Physical Evidence UnitEvidence Unit

I Can review the common types of physical I Can review the common types of physical evidence at crime scenes.evidence at crime scenes.

I Can explain the difference between the I Can explain the difference between the identification and comparison of physical identification and comparison of physical evidence.evidence.

I can define and contrast individual and class I can define and contrast individual and class characteristic of physical evidence.characteristic of physical evidence.

I can explain the value of class evidence as it I can explain the value of class evidence as it relates to a crime case.relates to a crime case.

I can list and explain the function of national I can list and explain the function of national databases available to forensic scientists. databases available to forensic scientists. Video

Edmond Locard (1877-1966)

French investigatorBackground in medicine and law1910-started a police laboratoryFounded Institute of Criminalistics at the University of LyonsContributed to fingerprints (poroscopy)

Locard’s Exchange Principle

1.Principle of cross-transfer2.Whenever two objects come into

contact there is evidence of that contact through cross-transfer…

3.Microscopic4.Macroscopic

Every contact leaves a trace!

PHYSICAL EVIDENCE CAN:PHYSICAL EVIDENCE CAN:

1. Prove that a crime has been committed or establish key elements of a crime. Example

Rape = victim has torn clothing, bruises, broken arm = non-consensual

2. Link a suspect with the victim or crime sceneExample : Burglary = suspect has broken glass shards in

his pants cuff that are consistent with glass shards at scene

3. Establish the identity of persons associated with a crimeExample : Latent fingerprints identified through AFIS. DNA

identified through CODIS.

PHYSICAL EVIDENCE CAN:PHYSICAL EVIDENCE CAN:

4. Exonerate the innocent. Example : Rape = DNA preserved was compared against man convicted of the crime = no match.

5. Corroborate the victim’s story. Example: Officer involved shootings during arresting a suspect.

6. Contradict information provided to investigators. Example : Discredit a witness; elicit a confession

7. Be more reliable than eyewitness testimony. “[Physical Evidence] does not forget. It is not confused by the excitement of the moment. It is not absent because human witnesses are. It is factual evidence. It cannot be wrong; it cannot perjure itself; it cannot be wholly absent. Only in it’s interpretation can there be error. Only human failure to find, study, and understand it can diminish its value.”

Paul Kirk, Crime Investigation, 1953

PHYSICAL EVIDENCE CAN:PHYSICAL EVIDENCE CAN:

8. 8. Be the cornerstone of a case. Police/prosecutors are expected to obtain physical evidence and rarely rely on a confession alone.

9. And IS expected by a jury/the public. TV, books, media focus on physical evidence and the miracles performed (reality vs. fantasy)

10. Support or refute a theory. The absence of forced entry in a burglary case…

Class and Individual Class and Individual Characteristics of EvidenceCharacteristics of Evidence

Class characteristics:Evidence can only be associated with

a group and not a unique sourceIndividual characteristics:

Evidence can be attributed to a unique source with a high degree of certainty (or even to the exclusion of all others)

Examples of Class Examples of Class CharacteristicsCharacteristics

1. Shoes (Tennis shoe; Nike)2. Paint (Cherry red car paint)3. Fibers ( polyester fiber, braided weave)4. Fingerprints (loops, whorls, arches)5. Toolmarks (knife scratch, screwdriver marks)6. Firearms (.40 caliber slug)7. Arson (accelerants)8. DNA (male…remember the sex genes; XY) or

the female XX genes in a genotype of the blood.

Individual Characteristics of Individual Characteristics of Evidence at a Crime SceneEvidence at a Crime Scene

1. Shoes (Nike Lunar Vapor 8 Tour Men's Tennis Shoe, size 7)

2. Paint (physical match with a identified car)3. Fibers (physical match, unique “trait” of a

particular garmet)4. Fingerprints (ridge detail enough for

database comparison)5. Toolmarks (unique stria markings)6. Firearms (stria matching a test fired bullet,

firing pin markings)7. DNA (profile that matches the suspect

identically.)

Value of Class Physical Value of Class Physical EvidenceEvidence

The value of class evidence lies in its ability to The value of class evidence lies in its ability to corroborate events in a manner that is nearly corroborate events in a manner that is nearly free of human error and bias. Class evidence free of human error and bias. Class evidence is not as specific as individual, but can is not as specific as individual, but can produce results that exclude a suspect.produce results that exclude a suspect.

As the number of different objects links an As the number of different objects links an individual to a crime scene.individual to a crime scene.

A person may be excluded or exonerated from A person may be excluded or exonerated from suspicion if physics evidence collected at a suspicion if physics evidence collected at a crime scene is found to be different from the crime scene is found to be different from the standard samples taken from the individual. standard samples taken from the individual. DNADNA

Common Types of Physical Common Types of Physical EvidenceEvidenceBiological Biological

Human / animal originsHuman / animal origins– Blood Blood – SalivaSaliva– SemenSemen– DNA hair profile.DNA hair profile.– Physiological fluidsPhysiological fluids– FingerprintsFingerprints– HairHair– Tissues Tissues – BodiesBodies

Type of Analysis of Blood, Semen,Type of Analysis of Blood, Semen, Saliva, Organs, & other Physiological Saliva, Organs, & other Physiological

FluidsFluids Origin – Comparison to known Origin – Comparison to known

suspects or witnesses, victims.suspects or witnesses, victims.DNA- Lab analysis to prove who DNA- Lab analysis to prove who

was there and who was not. was there and who was not. Condition- samples must be in Condition- samples must be in

good enough condition to be good enough condition to be analyzed. Watch for contamination analyzed. Watch for contamination with external chemicals / materials.with external chemicals / materials.

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Examples of Physical Examples of Physical Evidence being Individual Evidence being Individual

and Proofand Proof1. Pathology wound matches murder

weapon…2. Glass fragments found in burglar’s

coat pocket…3. Burglar’s tools…4. Poison found in suspect’s home

with rare component…

Fingerprints Fingerprints Mainstay of ForensicsMainstay of ForensicsWho is on file?Who is on file?

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HairHair

What type?What type?How removed?How removed?Match to a personMatch to a personDNADNA

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Impression Crime Scene Impression Crime Scene EvidenceEvidence

Tire Markings – types and sizes of tires, weightsTire Markings – types and sizes of tires, weights Shoe prints - tread, depth, weight, forcesShoe prints - tread, depth, weight, forces Depressions in soft soils- Remnants of actions Depressions in soft soils- Remnants of actions

and activities of numerous people or animals.and activities of numerous people or animals. All types of tracks- machines, animals, humans.All types of tracks- machines, animals, humans. Material ImpressionsMaterial Impressions

– Fabric- gloves, clothing, packs and cases.Fabric- gloves, clothing, packs and cases.– Tool marks- hand tools, machine parts, bullet riffling.Tool marks- hand tools, machine parts, bullet riffling.– Bite marks- human, dog, lions and tigers and bears!Bite marks- human, dog, lions and tigers and bears!– Impact impressions – car lisence plates, bumper Impact impressions – car lisence plates, bumper

shapes.shapes.– Soils, mud, waste residue.Soils, mud, waste residue.

ImpressionsImpressions

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Tool MarksTool Marks

Match tool to scaresMatch tool to scares

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Soils, Minerals, Wood, Soils, Minerals, Wood, and Other Vegetative and Other Vegetative

Matter. Matter. Location Location Link suspectLink suspectTrace Trace

EvidenceEvidence

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MANUFACTURED ITEMSMANUFACTURED ITEMS

These are man made items that are These are man made items that are very commonly found at the scene of a very commonly found at the scene of a crime.crime.– Weapons of all kinds: Firearms, ammo, Weapons of all kinds: Firearms, ammo,

knives, swords, machetes, chainsaws, knives, swords, machetes, chainsaws, ropes, explosives, bombs or components ropes, explosives, bombs or components like blasting caps.like blasting caps.

– Polymers, plastic bags, paint, glass, fibers, Polymers, plastic bags, paint, glass, fibers, petroleum products, vehicle headlights.petroleum products, vehicle headlights.

– Drugs, chemicals, Drugs, chemicals, – Documents or computer programs.Documents or computer programs.

Firearms and Firearms and AmmunitionAmmunition

Circumstances of Circumstances of dischargedischarge

Link to suspectLink to suspectLink to weaponLink to weaponLink to victimLink to victim

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Powder ResiduePowder ResidueEvidence of shootingEvidence of shootingCircumstances of Circumstances of shootingshooting

Type of weaponType of weapon

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DrugsDrugs Type of Drug?Type of Drug?Strength?Strength?Origin?Origin?Legal?Legal?

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Explosives & Explosives & PropellantsPropellants Link to suspect or Link to suspect or

victim by person, victim by person, place or thing.place or thing.

Origin; military, Origin; military, civilian?civilian?

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FibersFibers Link suspect Link suspect to a location to a location or victim by or victim by direct direct comparisoncomparison

Origin? Origin? Type?Type?

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GlassGlass How broken?How broken?Link a suspect to a crime Link a suspect to a crime scenescene

FingerprintsFingerprintsBlood; type.Blood; type.

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PaintPaint

OriginOriginMatchMatch

Documents Documents Hand writtenHand writtenType or PrintedType or PrintedAuthenticity?Authenticity?

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Types of Types of AnalysisAnalysis

ComparisonComparisonVisualVisual MicroscopicMicroscopicChemicalChemical

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ComparisonComparisonMost types of evidence require a Most types of evidence require a control with which to be comparedcontrol with which to be compared

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http://www.fbi.gov/about-us/cjis/fingerprints_biometrics/iafis/iafis

IDENTIFICATIONIDENTIFICATION

Identification has as its purpose the Identification has as its purpose the determination of the physical or chemical determination of the physical or chemical identity of a substance with near certainty identity of a substance with near certainty in accuracy. in accuracy. – Identify the substance and rule out any closely Identify the substance and rule out any closely

related substance. Ex. Drugs. Make sure it is related substance. Ex. Drugs. Make sure it is cocaine and not PCP.cocaine and not PCP.

– Standards within databases are compared by Standards within databases are compared by computer analysis to help speed things up.computer analysis to help speed things up. http://webbook.nist.gov/chemistry/ http://www.fbi.gov/about-us/cjis/http://www.fbi.gov/about-us/cjis/

fingerprints_biometrics/iafis/iafisfingerprints_biometrics/iafis/iafis

Visual Analysis Visual Analysis Evidence utilized through unaided Evidence utilized through unaided

observationobservation

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Microscopic AnalysisMicroscopic AnalysisEvidence observed with the use Evidence observed with the use

of some type of microscopeof some type of microscopebsapp.com

Chemical AnalysisChemical AnalysisEvidence subjected Evidence subjected

to any type of to any type of chemical procedurechemical procedure

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Forensic DatabasesForensic Databases

IAFISIAFIS CODISCODIS NIBINNIBIN PDQPDQ SICARSICAR

IAFIS DATABASEIAFIS DATABASE

The The IINTEGRATED NTEGRATED AAUTOMATED UTOMATED FFINGERPRINT INGERPRINT IIDENTIFICATION DENTIFICATION SSYSTEM.YSTEM.

Started by FBI in Started by FBI in 19991999

50 million 50 million people’s prints.people’s prints.

CODISCODIS

COCOMBINED MBINED DDNA NA IINDEX NDEX SSYSTEMYSTEM

Created by FBI in Created by FBI in 19981998

Compares the DNA Compares the DNA of known criminals of known criminals and crime scene and crime scene evidence.evidence.

7 million profiles7 million profiles

NIBINNIBIN NNATIONAL ATIONAL

IINTEGRATED NTEGRATED BBALLISTICS ALLISTICS IINFORMATION NFORMATION NNETWORK.ETWORK.

Made by Bureau of Made by Bureau of Alcohol, Tobacco, Alcohol, Tobacco, Firearms and Firearms and Explosives.Explosives.

900,000 samples.900,000 samples.

PDQPDQ

INTERNATIONAL INTERNATIONAL FORENSIC FORENSIC AUTOMOTIVE AUTOMOTIVE PPAINT AINT DDATA ATA QQUERY databaseUERY database

50000 paint 50000 paint samples samples analyzed for analyzed for standards.standards.

SICARSICAR

SSHOEPRINT HOEPRINT IIMAGE MAGE CACAPTURE AND PTURE AND RRETIEVAL DATABASEETIEVAL DATABASE

17000 different 17000 different patterns scanned so patterns scanned so far.far.

Allows for comparison Allows for comparison of foot prints at scene of foot prints at scene to known standards.to known standards.