Chapter 39 — Self-Check Quiz

25 questions: multiple choice and short answer. Try them closed-book. The answer key is in the collapsed block at the bottom. This is the capstone, so several questions ask you to weigh the whole file, not recall one fact.

Multiple choice

1. Forensic case assembly is best described as: - A. A summary that restates each finding in order - B. The combined evaluation of all evidence, each at its true strength, to reach the most defensible overall conclusion and mark its limits - C. The process of proving guilt beyond all doubt - D. The detective's narrative of how the crime occurred

2. The first rule of honest assembly is that a thread's strength, when combined with others: - A. Is upgraded because it now has corroboration - B. Is carried forward at exactly the strength it earned, and not one degree stronger - C. Becomes "proves" once three or more threads agree - D. No longer matters, because only the total counts

3. An exclusion matrix arrays: - A. Suspects against motives - B. Each person of interest against each line of evidence, marking excluded / consistent-with / not-applicable - C. Evidence against its cost to analyze - D. Crimes against their statutes of limitation

4. In the Mill Creek matrix, the person whose overall status is "not excluded" is: - A. Victor Salas - B. Dana Whitfield - C. Cody Renner - D. Roy Keller

5. Victor Salas was excluded by: - A. His confession - B. A DNA non-match and a verified alibi - C. The soil on his boots - D. The criminal profile

6. Cody Renner's row is the most important in the matrix because it shows that: - A. Confessions are always reliable - B. Three independent exclusions overrode a confession, preventing a wrongful conviction - C. Cell-site data is worthless - D. The fire was accidental after all

7. The unknown-stranger theory was closed by: - A. The autopsy - B. The pry marks - C. Investigative genetic genealogy / rapid DNA (the minor mixture contributor was not a stranger) - D. The neighbor's eyewitness identification

8. Convergence of evidence carries weight only to the degree that the threads are: - A. Numerous - B. Independent - C. Presented by the same expert - D. Collected at the scene

9. The classic circumstantial triad assembled against Keller is: - A. Motive, opportunity, means - B. Cause, manner, mechanism - C. Class, subclass, individual - D. Frye, Daubert, Kumho

10. The biological anchor against Keller is: - A. A single-source DNA match - B. A heat-degraded DNA mixture, consistent with his contribution, expressed as a likelihood ratio - C. A fingerprint individualized to him - D. A bite mark

11. "False convergence" most often arises when: - A. The threads are too few - B. A single shared cause — usually cognitive bias — produced threads that only appear independent - C. The lab is accredited - D. The evidence is all biological

12. The honest conclusion of the Mill Creek case is that the evidence: - A. Proves Keller is guilty - B. Strongly supports that Keller killed Diallo and staged the fire — but does not prove it - C. Is consistent with Keller but no stronger than with anyone else - D. Excludes Keller

13. "Strongly supports" rather than "proves" is chosen because: - A. The analyst is not confident - B. No number of limited threads (a mixture, class toolmarks, area-level location) sums to metaphysical certainty - C. The law requires the weaker word - D. The DNA was never tested

14. Why is Keller's status as a co-owner of the cabin a residual uncertainty? - A. It means he could not have been there - B. It gives an innocent explanation for the soil on his boots and the timing of his presence - C. It excludes him by alibi - D. It proves the fire was accidental

15. On the stand, an expert should leave which word to the jury? - A. "Consistent with" - B. "Strongly supports" - C. "Guilty" - D. "Excluded"

16. The criminal profile (Chapter 28) in the assembly is given: - A. The most weight, because profiling is highly validated - B. Equal weight with the DNA - C. No weight — it pointed away from Keller, and the science overruled it - D. Weight only if the jury agrees with it

17. The most valuable single further test named in §39.5 is: - A. Re-running the GSR test - B. Independent, blind re-examination of the contested interpretations - C. Interviewing Renner again - D. Re-photographing the scene

18. A further test counts as honest science only if: - A. It is guaranteed to confirm the conclusion - B. It could symmetrically strengthen or weaken the conclusion - C. It is cheap - D. The prosecutor approves it

19. Which finding most directly overturned the original "accidental fire" assumption? - A. The pollen on the floor mat - B. The autopsy's "no soot in the airways" — dead before the fire - C. The latent print on the gas can - D. The neighbor's identification

20. Treating every "forensic" thread as equally trustworthy would violate which theme? - A. Theme 1 (exclusion over proof) - B. Theme 2 (not all methods are equally valid) - C. Theme 4 (the CSI effect) - D. None — all forensic evidence is equally reliable

Short answer

21. In one sentence each, explain why "not excluded" is not the same as "guilty," and why the convergence is needed before anything stronger can be said.

22. State the Mill Creek conclusion in a single sentence at its true strength, then name two specific things that conclusion does not establish.

23. Explain the difference between genuine convergence and bias-driven convergence, and name the one property of the threads that, if lost, collapses the difference.

24. A defense attorney says the cell-site evidence "puts Keller's phone at the cabin." Correct this statement to its honest strength, and explain why the correction matters.

25. Why is the ability to list everything the conclusion does not establish a sign of competence rather than weakness? Tie your answer to one of the four themes.

Answer key (try the questions first) **Multiple choice** 1. **B** — assembly *weighs*; a summary merely restates. 2. **B** — the no-promotion rule; number of threads does not upgrade any one thread's verb. 3. **B** — persons × evidence, each cell marked excluded / consistent-with / n/a. 4. **D** — every test that excluded the others fails to exclude Keller. 5. **B** — two independent exclusions: biological (DNA non-match) and temporal (verified alibi). 6. **B** — three independent exclusions (DNA, cell-site, the dissected false confession) overrode a confession; the near-miss wrongful conviction. 7. **C** — IGG / rapid DNA established the minor contributor was not an unknown stranger (Chapter 29). 8. **B** — independence is the load-bearing condition; non-independent threads cannot be multiplied. 9. **A** — motive (Ch.27/18), opportunity (Ch.25/26/24/13), means (Ch.20/21–23/16). 10. **B** — a mixture interpreted as an LR, *consistent with* his contribution; not a single-source match. 11. **B** — a shared cause (usually bias) makes non-independent threads look independent (see the Beatrice Six, Case Study 39.2). 12. **B** — the frozen, honest framing: strongly supports, not proves. 13. **B** — limited threads (mixture, class toolmarks, area-level location, co-owner's soil) sum to strong support, never certainty. 14. **B** — a co-owner has innocent reasons to have walked the ground, so the soil cannot distinguish a guilty visit from an innocent one, nor fix *when* it was acquired. 15. **C** — "guilty" is a *legal* conclusion (the ultimate-issue problem, Chapter 30); the expert testifies to the *weight* of the evidence. 16. **C** — profiling is lowest on the validity spectrum; it pointed at a "lone drifter," away from Keller, and was correctly given no weight. 17. **B** — blind re-analysis does more than any single new test to neutralize the bias concession. 18. **B** — symmetry (could strengthen *or* weaken) is what makes the conclusion falsifiable, hence science. 19. **B** — the autopsy hinge: a living person in a fire breathes; no soot in the airways means dead before the fire. 20. **B** — Theme 2; weighing a debunked profile equally with DNA is exactly the error. **Short answer** 21. *"Not excluded"* means only that no test ruled him out; it is the absence of an exclusion, not the presence of proof. The convergence is needed because clearing the field leaves a *candidate*, and only the independent agreement of motive, opportunity, means, and the biological anchor turns "the one who remains" into "the one the evidence strongly supports." 22. Model: *"The evidence strongly supports that Roy Keller sedated Marcus Diallo, killed him by blunt-force trauma, and staged a gasoline fire to collect insurance — but does not prove it."* Does NOT establish (any two): that the DNA is a single-source match; that *Keller's specific* pry bar made the marks (class, not individual); that he (not just his phone) was at the cabin (not just the area); a *guilty* rather than innocent reason for a co-owner's soil; that the scene was uncompromised; that the original analysis was bias-free. 23. Genuine convergence = multiple *independent* methods, each blind to the others, agreeing; the agreement is improbable for an innocent person, so it carries weight. Bias-driven (false) convergence = threads that only *appear* to agree because one shared cause (cognitive bias / a decided-in-advance theory) bent all of them the same way. The property that collapses the difference if lost is **independence** — without it you cannot multiply improbabilities, and apparent agreement means nothing. 24. Honest version: *"The cell-site records place Keller's phone in the coverage *area* that includes the cabin — not at the cabin itself — during the relevant window, which contradicts his stated alibi an hour away."* It matters because upgrading "area" to "at the cabin," and "phone" to "the man," manufactures certainty the data does not contain — exactly the overstatement that has produced wrongful convictions (Chapter 25). 25. Because a conclusion that cannot specify its own limits is a *belief*, not a finding; the limits are what make it falsifiable and therefore scientific (Theme 1: the science is surest when it states exactly how far it reaches and no farther — and Theme 4: it resists both the fantasy of certainty and the cynical dismissal of strong-but-bounded evidence). Listing what the evidence does not show is the same discipline as reserving "proves" — it is honesty about reach.