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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Functions of the Forensic
Scientist
Forensic Scientists rely primarily on
scientific knowledge. However, only half
the job is performed in the laboratory
while the other half takes place in the
courtroom.
These functions fit into three categories:
Admissibility of Scientific
Evidence
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How does the court decide whether or not to
accept scientific evidence? The judge and
jury are typically not scientifically trained.
Several court cases illustrate the steps in the
development of admissibility.
Frye vs. United States
(1923)
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Scientific validity of polygraph is rejected
Court ruled that in order to be admitted as
evidence in trial the questioned procedure,
technique or procedure must be “generally
accepted” by a meaningful segment of the
scientific community.
Collection of experts called in to testify
about the validity of scientific issues
Books and papers written on subject
reviewed and discussed.
Federal Rules of Evidence
(1975):
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A code of evidence law governing the
admissibility of evidence in the U.S. federal
court system enacted in 1975.
Rule 702 applies to scientific, technical or
otherwise specialized knowledge.
Individual states are free to adopt different
evidence rules but most have codes that are
based on FRYE.
Courts traditionally use one of these rules
for the admissibility of scientific evidence:
 The
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Frye v. United States (1928) 293 F. 1013
 The
test
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Frye Test
Frye Test Plus or KELLY-Frye
People v. Kelly (1976) 17 Cal.3d 24
 Daubert
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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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Illinois Rules of Evidence Rule
702 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 in 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.
Where an expert witness testifies to an opinion based on a new or
novel scientific methodology or principle, the proponent of the
opinion has the burden of showing the methodology or
scientific principle on which the opinion is based is sufficiently
established to have gained general acceptance in the
particular field in which it belongs.
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Although there had been considerable
clamoring for Illinois to adopt the Daubert
test, as the Federal courts and many other
jurisdictions have done, the Illinois
Supreme Court has made it clear that it is
Frye and not Daubert that must be followed.
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 the
testimony is based upon
sufficient facts or data, the
testimony is the product of reliable
principles and methods, and the
witness has applied the principles
and methods reliably to the facts of
the case.
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The Frye test as set forth in Frye v. United States,
293 F. 1013 (D.C. Cir. 1923), is a specific test of
admissibility related to expert testimony
concerning scientific evidence. Where opinion
testimony is based on the expert’s personal
knowledge and practical experience, but not based
on “studies and tests,” it is not subject to a Frye
test. Donnellan v. First Student, Inc., 383 Ill. App. 3d
1040, 1061, 891 N.E.2d 463 (1st Dist. 2008). The
Frye test is also known as the “general acceptance”
test, as it requires that “the thing from which the
deduction is made must be sufficiently established
to have gained general acceptance in the
particular field in which it belongs.
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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. Dow Pharmaceuticals, Inc. (1993)
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“general acceptance” or Frye standard no
longer absolute prerequisite.
Trial judge given the task of ensuring an
expert testimony rests on a reliable
foundation, is relevant to case, and is not
repetitive, inflammatory or unnecessarily
confusing. (gatekeeper)
Daubert Ruling suggested areas of inquiry:
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Whether the scientific technique or theory
can be (and has been) tested.
Whether the technique or theory has been
subject to peer review & publication
The technique’s potential rate of error
The existence and maintenance of standards
Whether the scientific theory or method has
attracted widespread acceptance within a
relevant scientific community
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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Admissibility of Evidence
1923 Frye v. United States
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Scientific evidence is allowed
into the courtroom if it is
generally accepted by the
relevant scientific community.
The Frye standard does not
offer any guidance on reliability.
The evidence is presented in
the trial and the jury decides if it
can be used.
Known as general acceptance
standard.
1993 Daubert v. Dow
Admissibility is determined by:
 Whether the theory or
technique can be tested
 Whether the science has been
offered for peer review
 Whether the rate of error is
acceptable
 Whether the method at issue
enjoys widespread acceptance.
 Whether the opinion is relevant
to the issue
The judge decides if the evidence
can be entered into the trial.
Concerns about the Daubert Ruling:
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Abandoning Frye’s general acceptance test will
result in the introduction of absurd
pseudoscientific claims in court
Supreme Court rejected these concerns:
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The judicial system is capable
Through vigorous cross-examination, presentation
of contrary evidence and careful instruction on the
burden of proof are the traditional & appropriate
means of attacking shaky but admissible evidence.
Different methods-same results: “Frye in drag”