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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PHYSICAL EVIDENCE
Chapter 3
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Physical Evidence
Objectives:
1.Review the common types of physicalevidence encountered at a crime scene
2.Explain the difference between theidentification and comparison ofphysical evidence.
3.Define and contrast individual and classcharacteristics of physical evidence.
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
3-4
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Types of Physical Evidence
•Blood, semen, and saliva
•Documents
•Drugs
•Explosives
•Fibers
•Fingerprints
•Firearms andammunition
•Glass
•Hair
•Impressions
•Organs and physiologicalfluids
•Paint
•Petroleum products
•Plastic bags
•Plastic, rubber, and otherpolymers
•Powder residues
•Soil and minerals
•Tool marks
•Vehicle lights
•Wood and othervegetative matter
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Purpose of Examining Physical Evidence
•Physical evidence is examined foridentification or comparison purposes.
•Identification – the process ofdetermining a substance’s physical orchemical identity
•Comparison – the process of ascertainingwhether two or more objects have acommon origin
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Identification Examples
•Chemical compositions of substances thatare illicit drugs.
•Residue from a fire or explosion
•identification of blood, semen, hair, orwood
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Comparison Examples
•A hair found at a crime scenemay match a hair sample takenfrom a suspect
•A paint chip found on a hit-and-run victim’s clothing may matchpaint taken from s suspectsvehicle
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Comparison Characteristics
•Individual Characteristics
–Evidence that can be associated to acommon single source with anextremely high degree of probability
•Never 100 % certain
•High degree of probability
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Individual Characteristics
•Examples:
–fingerprints
–random striation markings on bullets or toolmarks
–irregular and random wear patterns in tireor footwear impressions
–handwriting characteristics
–the fitting together of the irregular edges ofbroken objects as in a jigsaw puzzle
–matching sequentially made plastic bags bystriation marks running across the bags
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Class Characteristics
•Class Characteristics
-evidence that can be associated only with agroup and not with a single source
•Examples:
-Blood types
-Paint from a car
-clothing fibers
-carpet fibers
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Using Physical Evidence
•As the number of different objects linking anindividual to a crime scene increases, so doesthe likelihood of that individual’s involvementwith the crime.
•Just as important, a person may be exoneratedor excluded from suspicion if physical evidencecollected at a crime scene is found to bedifferent from standard/reference samplescollected from that subject.
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Forensic Databases
•IAFIS-The Integrated Automated Fingerprint IdentificationSystem; a national fingerprint and criminal history systemmaintained by the FBI. (1999)
•CODIS – The Combined DNA Index System; enables federal,state, and local crime laboratories to electronically exchange andcompare DNA profiles; maintained by FBI (1998)
•NIBIN - The National Integrated Ballistics InformationNetwork; allows firearm analysts to acquire, digitize, andcompare markings made by a firearm on bullets and cartridgecasings. (ATF)
•PDQ - The International Forensic Automotive Paint DataQuery; database contains chemical and color informationpertaining to original automotive paints. (RCMP)
•SICAR - shoeprint image capture and retrieval; a shoeprintdatabase.
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Physical Evidence
Objective:
•Explain the purpose physical evidenceplays in reconstructing the eventssurrounding the commission of a crime.
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Crime Scene Reconstruction
•Reconstruction-the method used to support alikely sequence of events at a crime scene byobserving and evaluating physical evidence andstatements made by those involved with theincident
•The collection and documentation of physicalevidence plays a crucial role in reconstructingthe events that took place surrounding thecrime.
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Crime Scene Reconstruction
Who is involved in reconstruction?
•Medical examiners
•Criminalists/crime scene investigators
•Law enforcement
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PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
Reconstruction Examples
•Determining whether a body was moved afterdeath
•Determining whether a victim was clothed atthe time of death
•Analyzing bullet trajectory
•Analyzing blood spatter
•Determining the direction from whichprojectiles penetrated glass objects
•Estimating distance of a shooter from a target
•Locating gunshot residues on a suspect