Chapter 34 — Exercises

Work these without looking back at the chapter first; then check yourself. Items marked † have full worked solutions in the answers appendix. There are no answers in this file. The mix is recall, applied reasoning, evidence interpretation, "spot the overstatement," ethics dilemmas, and a cold-case extension. This chapter synthesizes the whole book, so several items deliberately reach back to earlier chapters.

A. Recall and definitions

  1. Define contributing factors to wrongful conviction in one sentence, and explain why the phrase is deliberately plural and uses the word contributing rather than cause.

  2. Define exoneree and distinguish it from the exoneration defined in Chapter 6. Why does naming the people, not just the cases, matter?

  3. † Define post-conviction review and explain, in two sentences, why an innocent person typically cannot get relief through the ordinary appeals process and must use this separate channel instead.

  4. Define a conviction integrity unit (CIU) and state the one feature, above all others, that determines whether a given CIU is genuine or merely cosmetic.

  5. List the five leading contributing factors to wrongful conviction identified in §34.2, and name the chapter in this book that treats each in depth.

  6. Which single contributing factor is the most common across the early DNA exonerations, and which is the one this book is principally about? Roughly how often does the forensic factor appear?

  7. Name the two real anchor cases this chapter uses to illustrate forensic failure, and state in a phrase which "sin" each one represents.

  8. What property of DNA testing (from Chapter 6) allowed it to audit the system's past convictions when a century of appeals could not?

B. Applied reasoning — the cascade

  1. † Draw or describe the wrongful-conviction cascade of §34.2 in your own words, beginning from a mistaken eyewitness identification. At each of the next four stages, name the contributing factor and state how it borrows credibility from the stage before it.

  2. Explain how a wrongful conviction can appear to rest on four independent pillars of evidence when, in fact, all four trace back to a single original error. Which step in the cascade is the original error?

  3. "Everyone involved acted in good faith, and an innocent person still went to prison." Explain why these two statements are compatible, and what that compatibility tells you about where a fix must be applied (i.e., why exhorting people to "be objective" is not enough).

  4. † A detective, having settled on a suspect early, stops pursuing leads that point elsewhere. Name this phenomenon, locate it in the cascade, and explain how it converts an honest investigation into one that manufactures a wrongful conviction.

  5. Explain, mechanically, how a false confession can come to contain "details only the killer would know." Where did the suspect actually learn those details? (Tie to Chapter 33.)

  6. Why is bad forensic evidence uniquely dangerous in the cascade compared to, say, a mistaken eyewitness — even though eyewitness error is more common? (Tie to the CSI effect, Chapter 1.)

C. Forensic science's specific role

  1. † Distinguish the two sins of forensic failure (the never-valid method vs. the overstated valid method). Give one real example of each from the chapter, and state the different fix each one requires.

  2. Why is a sincere bite-mark examiner who genuinely believes in his method more dangerous to an innocent defendant than a deliberate liar using a sound method? Explain the mechanism.

  3. The Cameron Todd Willingham case is the book's emblem of the first sin. State precisely what was wrong with the forensic evidence against him — was it overstated, or was it something worse? Connect your answer to modern fire science (Chapter 22).

  4. The Brandon Mayfield case is the book's emblem of the second sin. Latent-print comparison is foundationally valid (Chapter 6); explain how a foundationally valid method still produced a 100%-confident, 100%-wrong identification. Name the two failures (beyond the method) that combined.

  5. Mayfield was a near-miss — he was never convicted. Explain why his case is nonetheless the right anchor for a chapter about wrongful convictions, and draw the parallel to the cold case's near-miss.

  6. † Using the validity spectrum (Chapters 1 and 6), explain why the gap between bite marks and DNA — not the competence of any individual examiner — is what separated the methods that convicted several exonerees from the method that freed them.

D. Evidence interpretation

  1. Re-read Figure 34.2 ("Two pillars, one source"). State, for each of the two "independent" pillars, the single earlier error each one actually traces back to, and explain why the jury experienced them as mutually corroborating.

  2. A post-conviction DNA test excludes the convicted person but does not identify who did commit the crime. A prosecutor argues this is therefore "not proof of innocence" and the conviction should stand. Using §1.6 and §34.4, evaluate this argument honestly — what is right about it, and what is wrong?

  3. An examiner's trial testimony reads: "The defendant's print is the latent print; I identified it to him to the exclusion of all others, with a zero error rate." Identify three separate overstatements in this sentence, and rewrite it as a defensible comparison claim (Chapter 1, §1.4; Chapter 6).

  4. A case file shows: a confident eyewitness ID, a confession obtained after twelve hours, a hair "consistent with" the defendant, and a jailhouse informant. A new lawyer must decide where the case is weakest. Rank the four pillars from most to least likely to be unreliable, and justify your ranking using the relevant chapters.

E. Spot the overstatement / junk-science alert

  1. † A news report states: "Forensic science is responsible for most wrongful convictions." Identify what is inaccurate about this claim, and state the accurate version using the chapter's figures and the distinction between "most common" and "common."

  2. A reformer proposes fixing wrongful convictions caused by junk methods (like bite marks) by training bite-mark examiners better and standardizing their reports. Explain, using the two-sins framework, why this proposal misdiagnoses the problem and would leave the catastrophic failure in place.

  3. A prosecutor's office announces it has created a conviction integrity unit. List three questions you would ask to determine whether the unit is genuine or cosmetic, and state what answer to each would indicate a real unit.

  4. An official insists, after a clean DNA exclusion, that "the right person is still in prison — the DNA just doesn't tell the whole story." Name the cognitive mechanism at work (Chapter 31) and explain why it is the same mechanism that built the original cascade.

F. Ethics and reasoning

  1. † You are a forensic analyst. The detective tells you, before you examine an ambiguous latent print, that the suspect has confessed and an eyewitness has identified him. Explain the risk to your analysis (Chapter 31), describe the safeguard that should have prevented you from learning this, and state plainly what you should do now that you have learned it.

  2. Is a wrongful conviction a "defense issue" or a "public safety issue"? Argue that it is both, using the §34.6 point about the guilty going free. Why is "getting the right answer" the same project as "protecting the public"?

  3. A jurisdiction routinely destroys biological evidence shortly after conviction to save storage space. Explain, using §34.4, why this policy is lethal to the innocent specifically, and what it does to the biased-sample nature of the DNA exonerations (Chapter 6).

  4. An exoneree is freed after nineteen years but the state denies compensation on a procedural ground. Discuss what the field — including forensic scientists whose discipline contributed to such convictions — owes the exonerated, and why "clinical honesty" (the book's tone) is not the same as moral indifference.

G. Synthesis and validity spectrum

  1. † Show how all four of the book's themes converge in a single typical wrongful conviction. For each theme, name the specific feature of the wrongful conviction it describes and the practice that would counter it.

  2. Explain why this chapter is the deliberate bookend of Chapter 6. What did Chapter 6 set up (in both its argument and its Case File) that this chapter completes?

  3. A method sits high on the validity spectrum (e.g., fingerprints) yet contributes to a wrongful conviction. Using the three rules of the spectrum from Chapter 6 (position is a ceiling; the spectrum is question-specific; the honest verb tracks the position), explain how a high-validity method still produces a wrongful result.

H. Cold-case extension

  1. † Cold Case. Using only the three forensic threads named in this chapter's Case File (the autopsy timeline, the cell-site data, and the DNA exclusion), write the entry you would add to the Mill Creek workbook (Appendix I) for Cody Renner. State (a) the honest status at full strength, (b) which earlier chapter established each of the three threads, (c) why the confession does not override them, and (d) why this chapter stops short of naming who the science points toward instead.

  2. Cold Case extension. Map the early Mill Creek investigation onto the cascade of §34.2: identify the moment of tunnel vision, the role of the confession, and the point at which the physical evidence — had it been worked sooner — could have broken the chain. What single reform from §34.5 would most plausibly have prevented Renner's near-conviction?

  3. Cold Case, integrative. Renner is excluded. Explain, in plain terms, why "the science excludes Renner" is a stronger and cleaner statement than "the science suggests Renner is probably innocent," and connect this to the surest-voice asymmetry of §1.6. Then state why the same exclusion says nothing, by itself, about the guilt of any other person of interest.

I. Short writing

  1. In 150–200 words, explain to a newly seated juror why "the expert testified to a match, the witness was certain, and the defendant even confessed" is not the overwhelming proof it appears to be — and what questions a careful juror should ask instead.

  2. † In 150–200 words, write the case for blind, context-managed analysis (Chapter 31) as the single most important forensic reform to prevent the failures in this chapter. Explain what it costs, why it works, and why the fact that most labs still have not adopted it is itself the chapter's most damning finding.