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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.

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chapter 18
Chapter 18

Scientific Evidence

the use of 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 investigated.
    • Proving corpus delicti, or proof that a crime was committed.
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
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
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
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
  • 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 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?
daubert v merrell dow 1993
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.
daubert test requires federal judges to ascertain the following
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.
frye vs daubert
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
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 admissibility.
state vs federal
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
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 genetic fingerprinting.
dna genetic profiling cont
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.)
fbi s report on what police officers need to know about dna
FBI’s Report on What Police Officers Need to Know about DNA
  • Excellent resource for the Criminal Justice Student or Police Officer
cases where dna evidence did not carry the burden of proof
Cases where DNA Evidence Did Not Carry the Burden of Proof
  • O.J. Simpson murder trial
  • Former Teamster Union President, James Hoffa’s disappearance
  • See text for details
the military and dna
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
Other Ways of Using DNA to Identify Suspects
  • Using close DNA matches
  • Using animal DNA to link suspect to the crime scene
forensic entomology
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 body’s muscles occurring after death
Board of Forensic Entomology:
  • International Forensic Entomology links:
forensic odontology
Forensic Odontology
  • American Board of Forensic Odontology
  • 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
The International Association for Identification
  • 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
American Academy of Forensic Science
  • 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 fingerprinting
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:
  • As 40% of criminal homicides are unsolved, identification of weapons used in these crimes is critical.
sources of other scientific evidence
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
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