Chapter 18
Scientific Evidence
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The Use of Scientific Evidence
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Even though scientific evidence is not
infallible, it could contribute to an
investigation by:
 Providing a lead or leads to head a
criminal investigation in the right
direction.
 Providing information eliminating a
suspect as the person who committed
the crime being investigated.
 Proving corpus delicti, or proof that a
crime was committed.
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Providing the independent corroborative
evidence necessary to support a
confession.
 Establishing a link between the crime
scene and the suspect or between the
suspect and the victim of the crime.
 Proving one of the essential elements of
the crime being investigated.
 Affirming or disproving an alibi.
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Establishing the innocence of people not
involved in the crime.
Encouraging or inducing a person to make
a confession or an incriminating admission
when the person is confronted with
scientific evidence that incriminates them.
Providing reasonable suspicion or probable
cause.
Building such strong cases against
defendants that the number of guilty pleas
are increased, clearing court calendars and
permitting faster trials of contested cases.
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What Is Scientific Evidence?
Scientific evidence is most often
presented in court by an expert
witness testifying on expert
opinions. It also includes expert
testimony that goes beyond science.
The scientific expert is frequently
called upon to interpret results and
draw conclusions about what results
mean in the case being tried.
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Courts traditionally use one of these
rules for the admissibility of scientific
evidence:
 The Frye Test
 Frye v. United States (1928) 293 F. 1013
 The
Frye Test Plus or KELLYFrye test
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People v. Kelly (1976) 17 Cal.3d 24
 Daubert Test
 Daubert v. Merrell-Dow Pharmaceuticals, Inc.
509 U.S. 579, 113 S.Ct. 2786 (1993).
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Frye Standard, Frye v. U.S.
293 F. 1013 (D.C. Cir. 1923)
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Essentially, for the results of a
scientific technique to be admissible,
the technique must be sufficiently
established to have gained general
acceptance in its particular field.
This is referred to as the "general
acceptance" test by the scientific
community.
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Kelly-Frye Hearings
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Kelly-Frye hearings are preliminary hearings in
which the judge determines whether or not to
permit particular scientific evidence to be
presented to the jury during trial.
In a typical Kelly-Frye hearing, both the
proponent and the opponent of the scientific
technique bring in a parade of scientific experts
and present their best arguments for or against
the admissibility of the particular scientific
evidence involved.
California uses the Kelly-Frye Test
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The Daubert Test
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The court suggested the trial court
consider various factors to assess
scientific validity
Has the theory been tested?
Has it been subjected to peer review by other
scientists?
What is the theory’s or technique’s known or
potential rate of error?
Do standards controlling the application of
the theory or technique?
Is the theory or technique generally
accepted?
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Daubert v. Merrell Dow (1993)
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The Court “REJECTED” the more
basic Frye test of “general
acceptance” in the scientific
community.
Daubert requires an independent
judicial assessment of reliability .
This test requires special pretrial
hearings for scientific evidence and
special procedures on discovery.
This is a more stringent test that
requires knowledge of Type I and
Type II error rates, as well as validity
and reliability coefficients.
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Daubert test requires (federal) judges
to ascertain the following:
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(1) Whether the theory or technique is
capable of being or has been tested;
(2) Whether it has been subjected to
peer review and publication;
(3) The known or potential rate of error
in using a particular scientific technique
and the standards controlling the
technique's operation; and
(4) Whether the theory or technique is
generally accepted in the particular
scientific field.
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Frye vs. Daubert?
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In terms of DNA admissibility, the two major
differences between Frye and Daubert are:
(1) Daubert requires a consideration of error
rates, whereas Frye typically does not.
(2) In Frye jurisdictions, the debate over
how to calculate the significance of a
genetic match goes toward the admissibility
of the evidence, whereas in Daubert
jurisdictions, it goes toward the weight .
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Judicial Role in Daubert
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The essence of Daubert is that the
Supreme Court has deputized federal
district judges as "gatekeepers,"
authorizing them to exercise broad
discretion to exclude whatever
evidence they deem to not meet
scientific standards of admissibility.
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State vs. Federal
States can “choose” between the
tests and decide which to use as
their standard.
 Findings in a 2006 study showed
that many states use parts of the
Daubert test but not all.
 The Federal Courts must use
Daubert.
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DNA Genetic Profiling
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Deoxyribonucleic acid (DNA) testing has
become an important forensic tool for
linking suspects to a crime.
Equally importantly, DNA testing has made it
possible to eliminate a suspect in a crime,
sometimes even after the suspect has been
convicted of that crime (exculpatory
evidence).
DNA genetic profiling has received such
wide acceptance among criminal justice
professionals that it is frequently called
genetic fingerprinting.
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DNA Genetic Profiling (Cont.)
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Locus points: base pairs that vary from
one individual to the next can be located.
For example, where eye color is determined,
base pairs will join in a sequence that is
repeated.
Measuring the size of a repetitive sequence of
base pairs at many such locations gives a
fingerprint-like picture of the DNA chain,
since at these locations, the sequence of base
pairs varies among different individuals.
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The FBI Laboratory's Combined DNA Index
System (CODIS) blends forensic science and
computer technology into an effective tool for
solving violent crimes. CODIS enables state and
local crime laboratories to exchange and
compare DNA profiles electronically, thereby
linking serial violent crimes to each other and
to known sex offenders. (A DNA profile is the
set of genetic characteristics that result from
forensic DNA analysis.)
http://www.fbi.gov/hq/lab/codis/index1.htm
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FBI’s Report on What Police
Officers Need to Know about DNA
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http://www.ncjrs.org/pdffiles1/jr000249c.
pdf
Excellent resource for the Criminal Justice
Student or Police Officer
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Cases where DNA Evidence Did Not
Carry the Burden of Proof
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O.J. Simpson murder trial
Former Teamster Union President, James
Hoffa’s disappearance
See text for details
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The Military and DNA
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The U.S. military services are currently
asking families of service members to
submit DNA samples for aid in
identification of remains found (WWII and
the Korean and Vietnam Wars).
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Other Ways of Using DNA to
Identify Suspects
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Using close DNA matches
Using animal DNA to link suspect to the
crime scene
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Forensic Entomology
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Entomology is the study of insects.
Forensic Entomology is used to determine the time since
death on human cadavers and other facts surrounding the
death such as location, placement, movement of the body,
and information on the manner of death.
An estimate might be made at the crime scene based on
lividity of the body or the advance of rigor mortis.
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Lividity is the process of blood settlement within the body after
death
Rigor mortis is the stiffening of the body’s muscles occurring
after death
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Board of Forensic Entomology:
http://www.missouri.edu/~agwww/
entomology/
International Forensic Entomology
links:
http://folk.uio.no/mostarke/forens_
ent/forensic_entomology.html
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Forensic Odontology
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American Board of Forensic Odontology
http://www.abfo.org/
The objective of the Board is to establish,
enhance, and revise, as necessary, standards of
qualifications for those who practice forensic
odontology, and to certify as qualified specialists
those voluntary applicants who comply with the
requirements of the Board.
In this way, the Board aims to make available a
practical and equitable system for readily
identifying those persons professing to be
specialists in forensic odontology who possess the
requisite qualifications and competence.
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The International Association for
Identification
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http://www.theiai.org/
IAI has grown into the most prestigious
professional association of its kind in the world,
with more than 5,000 members from the United
States and many other countries. The
advancement of forensic disciplines through
education continues to be one of the top
priorities of the Association.
THE IAI also certifies forensic experts in a
variety of areas of expertise in Forensics.
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American Academy of Forensic
Science
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http://www.aafs.org/
As a professional society dedicated to the
application of science to the law, the AAFS
is committed to the promotion of
education and the elevation of accuracy,
precision, and specificity in the forensic
sciences.
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Ballistics Fingerprinting or Firearm
Fingerprinting
The rifling of the barrel of the gun leaves
unique marks in the lead or steel of the bullet
fragment.
This technology is often called ballistic
fingerprinting.
Technicians can then enter a digital image of
the tiny markings into a computer data base
called the National Integrated Ballistic
Information Network . The computer then spits
out likely matches which the examiners can
then study further under a microscope.
NIBIN on the web: http://www.nibin.gov/
As 40% of criminal homicides are unsolved,
identification of weapons used in these crimes
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is critical.
Sources of Other Scientific Evidence
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Other scientific evidence used regularly in courts
throughout the united states include:
Test for alcoholic intoxication
Fire and explosive science evidence
Forensic pathology
Chemistry, toxicology, serology
Microanalysis
Neutron activation analysis (NAA)
Tests used in questioned documents
Scientific detection of speeding
Accident Reconstruction
Forensic odontology
Accident reconstruction techniques
Physical anthropology
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Sources for Collecting, Correlating,
and Coordinating Evidence
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National Law Enforce Data Exchange (NDex)
Terrorist Screening Center
Combined DNA Index System (CODIS)
National Gang Threat Assessment and
Database
Hazardous Devices School
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