Chapter 18
 Scientific
Evidence
1
The use of scientific evidence




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 .

2
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.

3




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.
4
What is scientific evidence?
Scientific evidence is most often presented in
court by an expert witness testifying as to
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.
5
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

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).
6
Frye standard (Frye v. U.S.
293 F. 1013 (D.C. Cir. 1923)


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.
7
Kelly-Frye Hearings



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
8
The Daubert Test






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
9
Daubert v. Merrell Dow (1993)




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.
10
Daubert test requires (Federal) Judges
to ascertain the following:




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.
11
Frye v. Daubert?



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
12
Judicial Role in Daubert

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 not to meet
scientific standards of admissibility
13
State v Federal
 States
can “choose” between
the tests and decide on which
is “their” standard
 The Federal Courts must use
Daubert
14
DNA Genetic Profiling



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
15
genetic fingerprinting.
DNA Genetic Profiling cont….



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
16

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
17
FBI’s Report on What Police
Officers Need to Know about DNA


http://www.ncjrs.org/pdffiles1/jr000249c.
pdf
Excellent resource for the Criminal Justice
Student or Police Officer
18
Forensic Entomology





Entomology is the study of insects.
Forensic Entomology is used to determine the time
since death on human cadavers and also other facts
surrounding the death such as location, placement,
movement of the body and information on the
manner of death.
Board of Forensic Entomology:
http://www.missouri.edu/~agwww/entomolo
gy/
International Forensic Entomology links:
http://folk.uio.no/mostarke/forens_ent/forens
ic_entomology.html
19
Forensic Odontology




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
20
The International Association for
Identification



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.
21
American Academy of Forensic
Science


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
22
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/
23
Sources of other scientific evidence













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
24