Chapter 11 — 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, and a cold-case extension.

A. Recall and definitions

  1. Define forensic pathology in one sentence, and state the qualifications of a forensic pathologist (what training makes one).

  2. † Distinguish a medical examiner from a coroner. State at least two ways the difference can affect the quality and independence of a death investigation, and name what the 2009 NAS report recommended.

  3. List the five phases of a forensic autopsy in order, and state the one rule that governs the order of operations.

  4. Define cause of death, manner of death, and mechanism of death, and give one example of each for a single hypothetical death.

  5. † Name the five conventional manners of death used in the United States, and state which one is reserved for when the evidence does not permit a confident classification.

  6. Define livor mortis, rigor mortis, and algor mortis in one sentence each, and state the physical process behind each.

  7. Define the postmortem interval (PMI), and explain why the early-window estimate is always reported as a range rather than a single time.

  8. Distinguish antemortem, perimortem, and postmortem injury, and name the feature (the "vital reaction") that helps separate an injury inflicted in life from one inflicted after death.

  9. What is carboxyhemoglobin, and why is the blood sample drawn for it among the most important specimens in a fire death?

  10. Define soot in the airways as a forensic finding, and state precisely where in the airway the pathologist looks and why that location matters.

B. Applied reasoning

  1. A body is found lying face-down, but lividity (livor mortis) is fixed on the back and buttocks. State the most parsimonious inference and name which postmortem change revealed it. What does "fixed" mean, and roughly when does fixation occur?

  2. † Explain, step by step, why a person who is alive when a structure fire starts will tend to show both soot in the deep airways and an elevated carboxyhemoglobin, while a person already dead shows neither. Tie each finding to respiratory physiology.

  3. Rigor mortis is described as "treacherous" as a clock. Give two specific conditions that speed its onset and one that slows it, and explain why a pathologist must know the scene's temperature and the decedent's pre-death activity to read it.

  4. A pathologist certifies "exsanguination" as the cause of death on a death certificate. Explain why this is an error of the cause/mechanism distinction, and write a corrected cause-of-death line for a fatal stabbing.

  5. Two competent pathologists agree completely on the cause of death but disagree on the manner. Explain how this is possible — and even expected — and why it is not evidence that one of them is incompetent.

  6. Algor mortis is called the most quantifiable early clock. Explain the basic intuition (the cooling curve) and then name three scene factors that make a standard cooling estimate (which assumes a naked body in still air) wrong in practice.

  7. † A head injury is found at autopsy. Explain why the pathologist often cannot determine from the injury alone whether it resulted from an assault or a fall, and what kind of evidence is needed to bridge that gap. Connect this to the cause-versus-manner distinction.

  8. Why does the autopsy collect trace evidence, fingernail scrapings, and gunshot-residue samples before the body is washed? Name one piece of evidence that washing would destroy.

C. Evidence interpretation

  1. † Re-read Figure 11.1 ("One body, three different words"). For the gunshot case given, write the cause, the mechanism, and the candidate manners, and explain in one sentence why the mechanism is the least informative of the three for a court.

  2. Re-read Figure 11.2 ("The airways and the blood"). State the two findings, the single conclusion they converge on, and three things the figure explicitly says this evidence does not establish.

  3. An autopsy reports a skull fracture in a burned body and defers the determination of "blunt-force trauma vs. heat artifact" to the forensic anthropologist (Chapter 12). Explain why this deferral is the honest move and not a failure of the autopsy.

  4. A report states: "Carboxyhemoglobin saturation was low; the decedent was not breathing during the fire." Identify the part of this that is a strongly-supported physiological inference and the assumption it quietly relies on (what alternative explanations should have been considered and excluded?).

  5. A pathologist's report estimates time of death as a window of "roughly 12 to 24 hours before examination, given assumptions about ambient temperature." Identify three things this sentence does well — i.e., where it is appropriately honest.

D. Spot the overstatement / junk-science alert

  1. † A prosecutor's slide reads: "The medical examiner determined the victim died at 9:47 p.m." Identify the overstatement and rewrite it as an honest time-of-death statement from livor, rigor, and algor.

  2. An expert testifies: "The skull fracture proves this was a murder." Name the specific overstatement (which of the three death determinations is being misused) and give the defensible version.

  3. A television medical examiner glances at a body at the scene and announces both the exact time of death and that it was a homicide. Using §11.3 and §11.4, give two reasons this is backward from how real death investigation works.

  4. An analyst testifies that strangulation is certain because petechiae were present. Using §11.5, explain why petechiae alone are not diagnostic of asphyxia, and what makes asphyxia interpretation especially prone to overstatement.

  5. A report gives a confident, narrow time of death with no mention of the ambient temperature, the body's clothing, or the surface it lay on. List the missing elements that should make a reader distrust the estimate (compare the entomologist's false-precision decimal in §13.3, previewed).

E. Ethics and reasoning

  1. † A pathologist is told "the partner already confessed" before beginning the autopsy. Using the Cognitive-Bias Watch in §11.5 (and previewing Chapter 31), explain the risk, name the kind of finding most vulnerable to it, and describe the safeguard. Is a finding read blind worth more than one read knowing the investigative theory, even when they agree?

  2. In a coroner jurisdiction, an elected coroner with no medical training certifies a suspicious death as "accident" over the objection of the physician who performed the autopsy. Explain, using §11.1, why this is a structural problem, and what an opposing attorney could fairly make of it in court.

  3. The national shortage of forensic pathologists means many work caseloads above recommended limits. Explain why overwork itself is an error source in death investigation, and connect it to the Chapter 4 idea that lab (here, office) quality is the ceiling on the evidence.

  4. A pathologist certifies a manner of death as "homicide" but the cause as a firm physical finding (a contact gunshot wound). Explain why the pathologist can defend the cause robustly while conceding the manner is an opinion — and why honestly stating that difference is the science done right rather than a weakness.

F. Synthesis and validity spectrum

  1. † Place these four conclusions on the NAS 2009 / PCAST validity spectrum (more defensible → less), justifying each: (a) "dead before the fire" from absent airway soot + low carboxyhemoglobin (this chapter); (b) "the victim was kneeling when struck" from bloodstain area-of-origin (Chapter 10); (c) "these teeth made this bite mark" (Chapter 16, previewed); (d) a single-source nuclear DNA match (Chapter 7).

  2. Explain how the Chapter 10 finding (doorframe blood deposited before the fire; spatter inconsistent with collapse-in-fire) and this chapter's "dead before the fire" finding are independent lines of evidence that converge — and why convergence of independent evidence is a recurring source of strength in the book.

  3. In one paragraph, explain how this chapter advances at least two of the book's four themes (exclusion over proof; the validity spectrum; cognitive bias; the CSI effect cutting both ways). Name which themes and how.

G. Cold-case extension

  1. † Cold Case. Write the entry you would add to the Mill Creek evidence log (Appendix I) for the autopsy findings. State (a) the strongly-supported conclusion and its honest verb; (b) the manner-of-death amendment and why it is an opinion; (c) the finding that is deferred and to which chapter; and (d) at least three things the autopsy specifically does not establish (including who).

  2. Cold Case extension. The autopsy overturns the accidental-fire assumption but names no one. List three other evidence types, each owned by a later chapter, that the autopsy hands forward as open questions, and state the specific question each must answer (think: the skull fracture, the toxicology, the fire).

  3. Cold Case, integrative. Renner's confession (Chapter 6) "still hangs unexamined" and now sits against a homicide. Explain why the autopsy's confirmation that a homicide occurred does not, by itself, make the confession reliable — and name the kind of later evidence (preview Chapters 25, 33) that would be needed to test it.

H. Short writing

  1. In 150–200 words, explain to a juror why a real autopsy can establish "dead before the fire" with strong confidence but cannot, from the body alone, name who caused the death — using the cause-versus-manner distinction.

  2. † In 150–200 words, contrast the validity foundations of the "dead before the fire" determination with those of bloodstain pattern event-reconstruction (Chapter 10): what does each rest on, where is each strong, and why does the fire-death finding survive cross-examination so much better?