Chapter 6 Self-Check Quiz

Twenty-four questions: multiple choice and short answer. Answers and brief explanations are in the collapsed block at the bottom — try the whole quiz before opening it.

Multiple choice

  1. A "wrongful conviction," as this chapter defines it, is best described as: - A) Any conviction later reversed on appeal - B) The conviction of a factually innocent person - C) A conviction obtained through an illegal search - D) A conviction with a sentence later reduced

  2. The single forensic method the 2009 NAS report exempted from its central criticism was: - A) Latent fingerprint comparison - B) Microscopic hair comparison - C) Nuclear DNA analysis - D) Firearms/toolmark identification

  3. The Innocence Project was founded in 1992 by: - A) Edmond Locard and Calvin Goddard - B) Barry Scheck and Peter Neufeld - C) The National Academy of Sciences - D) The President's Council of Advisors on Science and Technology

  4. "Foundational validity," in the PCAST 2016 framework, is a property of: - A) The individual examiner's training - B) The specific case application - C) The method itself, established by empirical studies - D) The court that admits the testimony

  5. Forensic science was a contributing factor in approximately what share of the DNA exonerations? - A) About 5% - B) About 10% - C) About half - D) Essentially all

  6. A "black-box study," as PCAST uses the term, measures: - A) How an instrument works internally - B) How often examiners get comparisons right and wrong when ground truth is known - C) The chemical composition of an unknown - D) The chain of custody for an exhibit

  7. The most common single contributing factor across the early DNA exonerations was: - A) Mistaken eyewitness identification - B) Jailhouse informants - C) DNA contamination - D) Judicial error

  8. PCAST 2016 found that latent fingerprint comparison is: - A) Not foundationally valid and should be excluded - B) Foundationally valid, but with a measured, non-zero error rate - C) Foundationally valid with a true zero error rate - D) Identical in reliability to bite-mark comparison

  9. Of the following, the method PCAST 2016 found not foundationally valid (and saw little prospect of becoming so) was: - A) Single-source DNA - B) Instrumental drug chemistry - C) Bite-mark comparison - D) Latent fingerprints

  10. The phrase the 2009 NAS report used to describe the overall state of U.S. forensic science was:

    • A) "Scientifically airtight"
    • B) "Badly fragmented"
    • C) "Beyond reasonable doubt"
    • D) "Internationally standardized"

  11. "Junk science," as defined here, differs from fraud in that junk science:

    • A) Always involves a dishonest examiner
    • B) Refers to a hollow method that misleads even an honest examiner
    • C) Only occurs in DNA cases
    • D) Is always inadmissible

  12. The "zero error rate" claim, historically made for fingerprints, is best understood as:

    • A) A validated finding from black-box studies
    • B) A refusal to measure, not a measurement
    • C) A requirement of the Daubert standard
    • D) An acceptable courtroom statement after PCAST

  13. According to the chapter, the countable DNA exonerations are a biased sample because they systematically exclude:

    • A) Homicide cases
    • B) Cases that left no testable biological evidence
    • C) Cases with eyewitnesses
    • D) Cases tried in federal court

  14. "Validity as applied" refers to whether:

    • A) A method has ever been validated anywhere
    • B) A foundationally valid method was used correctly in the specific case
    • C) The court accepted the testimony
    • D) The examiner is board certified

  15. On the validity spectrum, as you move from the strong end toward the weak end, the strongest defensible verb moves from:

    • A) "Proves" toward "identifies"
    • B) "Identifies, with a probability" toward "the science does not support this comparison"
    • C) "Cannot exclude" toward "individualizes"
    • D) "Consistent with" toward "to the exclusion of all others"

  16. A discipline that sits at both ends of the validity spectrum depending on the question is:

    • A) Forensic toxicology
    • B) Forensic odontology (dental ID vs. bite marks)
    • C) Nuclear DNA analysis
    • D) Digital forensics

  17. The U.S. Supreme Court case holding there is no freestanding federal constitutional right to post-conviction DNA testing was:

    • A) Daubert v. Merrell Dow
    • B) District Attorney's Office v. Osborne
    • C) Frye v. United States
    • D) Kumho Tire v. Carmichael

  18. The reason casework cannot substitute for a validation study is that in real casework:

    • A) The samples are too small
    • B) You almost never learn the ground truth, so you cannot count your errors
    • C) The instruments are uncalibrated
    • D) Examiners are not trained

Short answer

  1. In two or three sentences, explain why exclusion — not proof — was the power that made the DNA exonerations possible.

  2. State the difference between foundational validity and validity as applied, and give one sentence showing how a foundationally valid method can still yield an invalid result in a specific case.

  3. Give the three rules for using the validity spectrum from §6.6.

  4. Explain the bias cascade: how can a mistaken eyewitness ID lead an honest forensic examiner to a mistaken "match," with no dishonesty anywhere in the chain?

  5. After PCAST 2016, what is the one additional element an examiner from a foundationally valid feature-comparison discipline must include when testifying to a match? Why?

  6. Why does the chapter call junk science "worse in a way" than fraud? Answer in two sentences.

Answer key (open after attempting all questions) 1. **B** — A wrongful conviction is the conviction of a factually innocent person; A, C, and D are reversals/changes that may apply to a guilty person. 2. **C** — Nuclear DNA analysis; it was built on validated, quantified, peer-reviewed science with known error rates. 3. **B** — Barry Scheck and Peter Neufeld, 1992, originally affiliated with the Cardozo School of Law. 4. **C** — The method itself, established by well-designed empirical studies, independent of the examiner. 5. **C** — About half of the DNA exonerations involved flawed or misapplied forensic science. 6. **B** — Many examiners, many comparisons with known ground truth, measuring the true error rate. 7. **A** — Mistaken eyewitness identification, present in a large majority of the early DNA cases. 8. **B** — Foundationally valid, but black-box studies revealed a real, non-zero false-positive rate. 9. **C** — Bite-mark comparison; PCAST found it not foundationally valid with little prospect of becoming so. 10. **B** — "Badly fragmented." 11. **B** — Junk science is a hollow method that misleads even an honest examiner; fraud involves dishonesty about results. 12. **B** — It is a refusal to measure; no human-judgment method has a true zero error rate. 13. **B** — Cases that left no testable biological evidence (e.g., many robberies built on eyewitness ID). 14. **B** — Whether a foundationally valid method was applied correctly in the specific case. 15. **B** — From "identifies, with a probability" toward "the science does not support this comparison." 16. **B** — Forensic odontology: reliable for dental identification of a body, discredited for bite-mark matching. 17. **B** — *District Attorney's Office v. Osborne* (2009). 18. **B** — In real casework you almost never learn ground truth, so errors go uncounted; validation needs known answers. 19. A single genetic mismatch at enough loci is, barring lab error, conclusive — it *excludes* the convicted person as the source of the crime-scene biology. Old trial evidence (an eyewitness, a hair "match") could be argued about; a clean exclusion could not. Exclusion is forensic science's surest voice (cf. §1.6). 20. **Foundational validity** = the method works, shown by empirical studies, with a measured error rate (a property of the method). **Validity as applied** = the method was used correctly in this case by a competent examiner within validated conditions. Example: single-source DNA is foundationally valid, but a contaminated or mislabeled sample yields an invalid result in that particular case. 21. (1) Position is a ceiling, not a guarantee. (2) The spectrum is question-specific (ask about the specific claim, not the discipline). (3) The honest verb tracks the position (match your testimony's strength to the method's place). 22. The mistaken eyewitness tells the detective who the suspect is; the detective tells the lab; the examiner, now knowing the "expected" answer, resolves an ambiguous comparison in that direction through ordinary confirmation bias; the bolstered "match" then makes the eyewitness look more reliable. Each error borrows credibility from the others — no dishonesty required (cf. Chapter 31). 23. The relevant error rate from the validation/black-box studies. PCAST held that a match may be reported only with its measured error rate — not as "individualization," "zero error," or "a reasonable degree of scientific certainty." 24. Because the method itself is hollow, an honest examiner using it in perfect good faith will still mislead the jury — and the examiner's sincerity makes the testimony *more* persuasive, hence more dangerous, than an obvious fraud.