Forensic Science
An Introduction
What is forensic science?
 Science
applied to the law or in a
legal arena
 “…the
application of science to
those criminal and civil laws that
are enforced by police agencies in
the criminal justice system.”
Saferstein
What is a key concept in FS?
 Locard’s
(~1910)
Exchange Principle
 Whenever
a criminal comes in
contact with a person or object
there is a cross-transfer of
evidence.
What are the consequences of
Locard’s Exchange Principle?
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The perpetrator leaves
evidence behind and also
takes evidence away
The longer you wait
before collecting evidence
the less there is left
Every person at the crime
scene including police
investigators will
contaminate it
Realistic?
What is Forensic Science Trying to
Do?

The goal of Forensic Chemistry is to
determine the provenance of a sample.

Link it to a person, place or thing
prov·e·nance
Pronunciation: 'präv-n&n(t)s, 'prä-v&-"nän(t)s
Function: noun
Etymology: French, from provenir to come forth, originate, from Latin
provenire, from pro- forth + venire to come -- more at PRO-, COME
1 : ORIGIN, SOURCE
2 : the history of ownership of a valued object or work of art or literature
The Crime Lab
Physical
Science
Firearms
Biology
Photography
Documents
Pathologist
Crime
Lab
Odontologist
Voiceprint
Analysis
Engineer
Polygraph
Latent
Fingerprints
Toxicology
Evidence
Collection
Anthropologist
Entomologist
Psychiatrist
Crime lab organization
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Departments in the crime lab
Biological evidence- examples?
Trace evidence- examples?
Document examination
Photographs
Computer technology evidence
Ballistics and firearms
Others?
Anthrax Letters
5 dead
17 sickened
What types of evidence would you look for?
Anthrax Letters
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Trace hair and fibers in envelope
Ink analysis may reveal manufacturer
DNA from stamp or envelope seal
Cellophane tape ends match over four letters
Paper examination may identify manufacturer
Fingerprints
Photocopier toner may reveal manufacturer
Handwriting analysis shows four letters written by same
person
Indented writing
Bar codes for mail handling
Analytic vs. Forensic Chemistry
Similarities
Analytic
 Wants to find
composition of
samples
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Forensic
 Wants to find
composition of
samples
Compounds
Proportions in
mixtures
Uses same
instruments as
forensic
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Compounds
Proportions in
mixtures
Uses same
instruments as
analytical
Analytic vs. Forensic Chemistry
Differences
Analytic
Forensic
 Known source
 Need to determine
source
 Good idea of what the
composition is likely
 Little knowledge of
to be
composition
 Used for quality
 Often complex
control
mixtures so hard to
find appropriate
 Well defined samples
controls
and controls
Roles of the Forensic Scientist
Analyze physical evidence
 Provide expert testimony
 Train evidence collection units in
recognition, collection and
preservation of evidence

The Expert Witness
 An
expert witness can testify as
to his/her opinion of what the
evidence indicates
 A lay witness can only testify as
to fact
The Expert Witness

Trial judge must be satisfied that the
expert

Has skill or knowledge that will aid the court
in determining the truth
Education (degrees, courses)
 Training (internship under experienced
practitioner)
 Experience (years on the job, publications,
professional societies)
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Trial judge is the gatekeeper
The Expert Witness
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Jury assigns weight to the expert’s
opinions
Jury looks at
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Credentials
Demeanor
Whether material is presented simply and
clearly
Jury is the trier of fact
A Big Driver in the Plot
 Can
the evidence be admitted
into court?
Admissibility: A Moving Target
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Frye v. US (1923)
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Scientific evidence is admissible only if it has
gained general acceptance in the field
Rejected polygraph opinions
Historical Perspective
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Tennessee v. John Scopes (1925)
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The Monkey Trial
Admissibility: A Moving Target
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Federal Rule of Evidence 702 (1975)
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Approved by Congress
More flexible general relevance test for admissibility
of opinion testimony by experts
“If scientific, technical or other specialized knowledge
will assist the trier of fact to understand the evidence
or to determine a fact at issue, a witness qualified as
an expert by knowledge, skill, experience, training, or
education, may testify thereto in the form of an
opinion or otherwise.”
Admissibility: A Moving Target
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Daubert v. Merrell Dow Pharmaceuticals (1993)
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When expert evidence based on “scientific
knowledge” is offered at trial, the judge acts as
gatekeeper to determine if the evidence is “reliable”
Four suggested factors in determining reliability
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Testable using the scientific method
Peer reviewed
Error rates
Acceptability to the scientific community
Trial judge given lots of flexibility
Muddy waters—what is scientific knowledge?
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What about other types of experts?
Admissibility: A Moving Target
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Why Daubert won on appeal
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When Congress passed Rule 702 it ignored
the Frye general acceptability criterion
Frye was no longer “good law”--
Admissibility: A Moving Target
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Kumho Tire Co v. Carmichael (1999)
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Daubert factors are extended to non-scientist
expert witnesses.
Daubert factors are not the only ones that can
be considered
Trial judge now has enormous flexibility
And it’s not settled yet…..
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Daubert and Kumho apply to federal cases
only
18 State Courts have adopted Daubert
standards
Other State Courts have rejected Daubert
and still use a modified Frye standard
What’s driving the growth of FS?
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Miranda decision
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Increase in drug seizures and arrests
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More testing
DNA profiling
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Fewer confessions
More testing with sophisticated equipment
Other new technologies
Miranda vs. Arizona (1966)
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Before questioning by the
police, suspects must be
informed that they have:
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The right to remain silent
The right to consult an attorney
If indigent an attorney will be
provided for them
Anything they say may be used
against them in court
Arizona Department of
Library Archives and Public
Records)
Dickerson
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Dickerson vs US (2000)
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Congress passed law in 1968 saying voluntary
confessions are exempt from Miranda
Supreme Court overrules Congress in 2000
Congress can’t overrule the Supreme Court on
constitutionally guaranteed rights except by
the amendment process
Results of Miranda
 Confessions
are less likely to hold
up in court since the burden of
proof of Miranda statement lies
on police
 Police and prosecutors rely more
independent (scientific) evidence
to prove guilt
What is the most common task a
forensic scientist performs?
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Take 5 minutes and discuss this in groups
of 4 and then be ready to report out your
reasoning.
Crime Wave or Better
Enforcement?
Federal Drug Seizures
Arrests by Drug Type
The Economics of Drugs
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According to the United Nations Office on Drugs and
Crime, "[T]he value of the global illicit drug market for
the year 2003 was estimated at US$13 bn [billion] at the
production level, at $94 bn at the wholesale level (taking
seizures into account), and at US$322bn based on retail
prices and taking seizures and other losses into
account."
This is larger than the total economies of 88% of the
countries in the world!
Source: United Nations Office on Drugs and Crime
(UNODC), World Drug Report 2005 (Vienna, Austria:
UNODC, June 2005), p. 127.
Average % THC in Marijuana
Seizures
Recent seizures in Atlanta had plants with 18% THC content.
http://www.usdoj.gov/ndic/pubs11/18862/images/fig1.gif
The Forensic All Stars
Mathieu Orfila (1787-1853)
Father of toxicology
Alphonse Bertillon (1853-1914)
First system of personal identification
Francis Galton (1822-1911)
Classification of fingerprints
Dr. Karl Landsteiner(1868-1943)
Determination of blood groups
Nobel Prize
Alphonse Bertillon’s work in
human stature
The Forensic All Stars
Calvin Goddard (1891-1955)
Father of ballistics
Use of comparison microscope
Albert S. Osborn (1858-1946)
Fundamental principles of document
examination
Walter C. McCrone (1916-2002)
Application of microscopy to analytic
problems
The Forensic All Stars
Hans Gross (1847-1915)
First text detailing application of science to
criminal investigation
Edmond Locard (1877-1966)
Locard’s Exchange Principle
There is an exchange of materials whenever two
objects come in contact
Who are the all-stars now?
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Dr. Henry Lee
Dr. Michael Baden
Dr. Bill Bass
Others?
The River Dell Doctor
Dr. Jascelevich
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Charged with 1st degree murder of
patients.
Trial led to mistrial as evidence was
lacking.
Curare muscle relaxer. Used on patients
but also used for research on animals by
Dr. J
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Scientific tests for the presence of by
product of curare insuffiencient.
Mistrial- charges dismissed
Second trial 10 yrs. Later b/c tests for by
product of curare now sufficient.
Exhumed bodies- only some chemical
found.
Acquitted
What is Science?
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An organized body of knowledge about
nature
A method for exploring nature and the
order in it
A set of tools for solving problems about
nature