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Scientific Evidence


Chapter 18 Scientific Evidence The Use of Scientific Evidence Even though scientific evidence is not infallible, it could contribute to an investigation by: Providing ... – PowerPoint PPT presentation

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Title: Scientific Evidence

Chapter 18
  • Scientific Evidence

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
  • Proving corpus delicti, or proof that a crime was

  • 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.

  • 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.

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.

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 KELLY-Frye 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).

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.

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

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
  • What is the theorys or techniques known or
    potential rate of error?
  • Do standards controlling the application of the
    theory or technique?
  • Is the theory or technique generally accepted?

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
  • This is a more stringent test that requires
    knowledge of Type I and Type II error rates, as
    well as validity and reliability coefficients.

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
  • (4) Whether the theory or technique is generally
    accepted in the particular scientific field.

Frye vs. 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 .

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
    to not meet scientific standards of

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.

DNA Genetic Profiling
  • Deoxyribonucleic acid (DNA) testing has become an
    important forensic tool for linking suspects to a
  • 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

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.

  • 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//

FBIs Report on What Police Officers Need to Know
about DNA
  • http//
  • Excellent resource for the Criminal Justice
    Student or Police Officer

Cases where DNA Evidence Did Not Carry the Burden
of Proof
  • O.J. Simpson murder trial
  • Former Teamster Union President, James Hoffas
  • See text for details

The Military and DNA
  • 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).

Other Ways of Using DNA to Identify Suspects
  • Using close DNA matches
  • Using animal DNA to link suspect to the crime

Forensic Entomology
  • 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.
  • Lividity is the process of blood settlement
    within the body after death
  • Rigor mortis is the stiffening of the bodys
    muscles occurring after death

  • Board of Forensic Entomology
  • http//
  • International Forensic Entomology links

Forensic Odontology
  • American Board of Forensic Odontology
  • http//
  • 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.

The International Association for Identification
  • http//
  • 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.

American Academy of Forensic Science
  • http//
  • 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.

Ballistics Fingerprinting or Firearm
  • The rifling of the barrel of the gun leaves
    unique marks in the lead or steel of the bullet
  • This technology is often called ballistic
  • 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//
  • As 40 of criminal homicides are unsolved,
    identification of weapons used in these crimes is

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

Sources for Collecting, Correlating, and
Coordinating Evidence
  • National Law Enforce Data Exchange (N-Dex)
  • Terrorist Screening Center
  • Combined DNA Index System (CODIS)
  • National Gang Threat Assessment and Database
  • Hazardous Devices School