Appendix 19

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Appendix 19

• DNA

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THE PRESENTATION OF DNA EVIDENCE IN COURT
Alan Giusti DNA Analysis Unit I FBI Laboratory,
Washington, D.C.
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The Presentation of DNA Evidence

• Admissibility Hearings
• Direct Examination
• Cross Examination Issues
• Outside Experts
• Trial Presentation
• Direct Examination
• Cross Examination Issues
• Redirect
• Outside Experts/Rebuttal Witnesses

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Presentation of Evidence

• BE PREPARED!
• Extensive documentation of analyses conducted.
• Strict adherence to protocols
• Trials can be one to two years after lab work
  completed thorough notes and adherence to the
  protocol greatly reduces expert witnesss
  uncertainty during testimony
• Pre-trial consultations and meetings critical!

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Types of Evidence

• Cigarette butts, stamps, envelopes
• chewing gum, threads
• baseball caps, ski masks, headbands
• Small blood spatter, fingernail clippings
• fecal material, vomit
• toothbrushes, hair brushes, eyeglasses
• phone receivers, pens, false teeth

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Presentation of Evidence at Trial

• KISS (Keep it simple, stupid)
• Brief description of DNA testing process (15-20
  minutes)
• Introduction of evidence and findings of
  serological examinations (if applicable)
• Results of DNA examinations
• Conclusions drawn from DNA tests
• Significance of a DNA match

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DIRECT EXAMINATION

• What is DNA?
• Can DNA be used to distinguish individuals?
• How is this done?
• What are the possible outcomes of a DNA
  comparison?
• What is the significance of a DNA match?

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DIRECT EXAMINATION

• What items of evidence did you examine?
• What did you find?
• What is the significance of the match?

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Source Attribution(The Identity Calculation)

• This calculation is used to determine if a DNA
  profile is so rare that it becomes unreasonable
  to suppose that a second person in the population
  might have the same profile.

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Source Attribution(The Identity Calculation)

• The conclusion drawn by the analyst is that an
  individual is the source of the DNA obtained from
  a forensic unknown, to a reasonable degree of
  scientific certainty.
• It does not mean that the DNA profile is unique
  to the exclusion of all others.

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Presentation of Evidence at Trial

• Depending on number of items tested, direct
  testimony of DNA evidence can be completed in 30
  minutes to 1 hour

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Cross Examination Topics

• Contamination at crime scene / during evidence
  collection
• Contamination by laboratory
• Error rates
• When DNA was deposited
• Consent (sexual assault cases)

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Cross Examination Topics

• Population databases/ethnic background of
  defendant
• It was the brother/father/uncle/etc.
• Reliability of the technology - quality control
  issues

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Redirect

• Recognize topics where testimony of DNA analyst
  may be limited by opposing counsel (Just answer
  yes or no, please)
• Attack hypothetical arguments
• If applicable, emphasize possibility of
  re-testing specimens, or testing of other
  relatives

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Outside Experts

• Scientists in the fields of molecular biology and
  population genetics will generally support
  technology and findings
• Can be used also to contradict outside experts of
  opposing counsel
• Pre-trial preparation - small group of defense
  experts with standard approaches - easily rebutted

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Admissibility of New Technologies

• Daubert v. Merrell Dow Pharmaceuticals (1993)
• Federal standard for acceptance of new
  technologies.
• Trial judge acts as gatekeeper - determines
  admissibility of scientific evidence/expert
  testimony.

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Daubert Conditions

• Scientific validation
• Peer review
• Reliability
• General acceptance in relevant scientific
  community
• Judge determines degree of emphasis for each
  condition.

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Scientific Validation

• Extensive research in the development of a new
  technology.
• Once process developed, reliability of technology
  determined by repetitive experiments - same
  results from a sample every time.

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Scientific Validation

• For forensic applications, technology applied to
  types of materials collected from crime scenes.
• Simulated samples Laboratory prepared samples
  subjected to chemical and environmental insults.
• Actual case specimens from adjudicated cases.

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Peer Review

• Publications in appropriate scientific journals.
• Presentations at scientific meetings/conventions.

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Reliability

• Error rate in the performance of the test, what
  percentage of the time will the test give an
  incorrect answer?
• False inclusion most serious error in forensic
  human DNA analysis.
• Failure to identify a virulent pathogen (false
  exclusion) equally dire.

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Reliability

• Reliability of test should be determined during
  development and validation phase.
• Current human DNA analysis protocols designed to
  avoid errors - numerous check points during
  procedures.
• Errors can occur during test, but there is no
  fixed error rate.

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General Acceptance

• Adoption of technology by relevant scientific
  community.
• Application of technology in other areas/fields -
  overarching acceptance of technology.
• Ex. PCR process used in many areas (medical,
  academic, forensic, etc.)
• Specific application, e.g., forensic DNA
  analysis, may be debated.

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Admissibility

• Be prepared to support technology with extensive
  documentation
• Detailed protocols
• RD and validation studies
• Relevant publication references
• Work of your own lab and other labs that have
  conducted research in the field.

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NRC I
First Report Issued by National Academy
of Sciences in 1992

• Methods Reliable

• 3-4 probe match rare

• Use product rule

• Ceiling principle

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NRC II
Second report issued in May of 1996

• Report actual frequency

• Recommended re-test

• Suggested identity

• The Bible

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Break
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WHAT IS DNA???

• Deoxyribonucleic Acid
• Genetic Blue print
• Unique to you unless you have an identical twin
• Robust molecule that can be obtained from
  evidentiary stains and tissues
• 99.9 of DNA is IDENTICAL in all people!

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New individual formed during conception ½ of
DNA from mother, ½ from father
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Review of DNA Structure
CHROMOSOME
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Complementary Base Pairs
A
T
Adenine
Thymine
T
A
Guanine
Cytosine
G
C
C
G
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HUMAN IDENTITY TESTING IS BASED ON POLYMORPHISMS
POLYMORPHISM MANY FORMS
DIFFERENCES BETWEEN/AMONG INDIVIDUALS
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Examples of Human Polymorphisms

• Hair color
• Eye color
• Height
• Blood type (ABO, Rh, etc.)
• Tissue type (HLA)

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TYPES OF DNA POLYMORPHISMS

• Sequence Polymorphism
• The cat is in the hat.
• The rat is in the hat.

• Length Polymorphism
• The cat ran very fast.
• The cat ran very, very fast.

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Length Polymorphisms

• MOST COMMONLY OCCURRING ARE VARIABLE NUMBER OF
  TANDEM REPEAT VNTR TYPE

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Polymerase Chain Reaction

• Molecular Xeroxing of targeted areas of DNA
  determined to contain information.
• Used in
• research
• diagnostics
• forensics

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PCR Typing

• Typing based on sequence differences (dots)
• DQ alpha typing
• Polymarker
• Interpretation Difficulties
• Typing based on length differences (bands)
• VNTRs (D1S80, amelogenin)
• STRs

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Short Tandem Repeats
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Short Tandem Repeats

• Arrays of short repeats (2-7 bp) that are
  repeated several times in tandem
• gt30,000 in the human genome
• One every 10 kb

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Allele
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5
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6
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