ABFM Case Analysis & Practical Application 3 — Questions and Answers
Question 1: A body is recovered from a house fire with severe charring. At autopsy, which finding definitively indicates the victim was alive during the fire?
- Pugilistic posturing of the extremities
- Epidural hematoma with heat fractures of the skull
- Carbon monoxide saturation of 60% in blood (Correct answer)
- Skin splitting and fat boiling artifacts
Correct answer: Carbon monoxide saturation of 60% in blood
Elevated carboxyhemoglobin (carbon monoxide saturation) in blood proves the victim was alive and breathing during the fire, as CO accumulates only through respiration.
Question 2: In a sexual assault case, a forensic nurse collects a vaginal swab 72 hours post-assault. Which biological material is most likely to still yield a male DNA profile?
- Motile spermatozoa
- Non-motile spermatozoa heads (Correct answer)
- Prostate-specific antigen (PSA)
- Seminal vesicle-specific antigen (SVSA)
Correct answer: Non-motile spermatozoa heads
Non-motile sperm heads with intact DNA can persist in the vaginal vault for up to 72–96 hours, whereas motility ceases within hours and PSA degrades more rapidly.
Question 3: A forensic expert testifies about blood spatter at a homicide scene. Low-velocity impact spatter measuring 6–10 mm in diameter with circular to slightly elliptical shapes most likely resulted from:
- An arterial gushing wound
- A gunshot exit wound
- Blunt force trauma at walking speed (Correct answer)
- Cast-off blood from a swinging weapon
Correct answer: Blunt force trauma at walking speed
Low-velocity impact spatter (6–10 mm diameter, rounded) is characteristic of dripping blood or blunt force trauma at low velocities, not high-velocity gunshot wounds.
Question 4: An inmate is found unconscious in a cell with miosis, bradycardia, excessive salivation, and bronchospasm. Toxicology shows a cholinesterase level of 15% of normal. What is the most likely cause?
- Heroin overdose obtained by smuggling
- Organophosphate poisoning from contraband pesticide (Correct answer)
- Tricyclic antidepressant toxicity
- Gamma-hydroxybutyrate (GHB) ingestion
Correct answer: Organophosphate poisoning from contraband pesticide
Cholinergic toxidrome with depressed cholinesterase activity is pathognomonic for organophosphate poisoning, which inhibits acetylcholinesterase.
Question 5: A forensic anthropologist is asked to determine age-at-death from skeletal remains of an adult. Which skeletal indicator provides the most reliable estimate for individuals over age 50?
- Fusion of the medial clavicular epiphysis
- Degree of cranial suture closure
- Pubic symphysis morphology using Suchey-Brooks method
- Dental root translucency (Correct answer)
Correct answer: Dental root translucency
Dental root translucency increases predictably with age and provides the most accurate estimates for individuals over 50 when multiple skeletal age markers converge.
Question 6: During a custody dispute, a physician alleges a child has been sexually abused based solely on a finding of a posterior hymenal transection. What is the most appropriate forensic response?
- Immediately report to child protective services and law enforcement
- Document that posterior hymenal transections are definitive of penetrating trauma
- Note that this finding is suspicious but requires correlation with history and behavioral findings (Correct answer)
- Obtain a colposcopy and conclude that abuse has occurred
Correct answer: Note that this finding is suspicious but requires correlation with history and behavioral findings
A posterior hymenal transection is suspicious for penetrating trauma but must be interpreted in the context of history and behavioral indicators, as no single genital finding is definitively diagnostic of abuse.
Question 7: A forensic toxicologist is asked about the significance of a blood benzodiazepine level detected post-mortem. Which factor most complicates interpretation?
- Benzodiazepines are rapidly metabolized before death
- Post-mortem redistribution can significantly elevate blood levels compared to ante-mortem levels (Correct answer)
- Benzodiazepines are not detectable in vitreous humor
- Urine benzodiazepine screening is more sensitive than blood testing
Correct answer: Post-mortem redistribution can significantly elevate blood levels compared to ante-mortem levels
Post-mortem redistribution from drug-rich tissues (brain, liver) into central blood can dramatically elevate benzodiazepine levels above those present at the time of death.
ABFM Case Analysis & Practical Application 3
A body is recovered from a house fire with severe charring.
At autopsy, which finding definitively indicates the victim was alive during the fire?