DHA Forensic Medicine exam questions

6 worked Forensic Medicine practice questions

Original exam-style questions from the bank, spread across the blueprint domains. They are not real or recalled exam questions. Try each one, then open the answer for the rationale and reference. None of them appear in the free mock exam, so reading them will not spoil it.

1. Question 1 · Asphyxia and Drowning

   A decomposed body is recovered from a river. The pathologist considers a diatom test. Which sample gives the most meaningful result for supporting drowning?

   1. ALung tissue from the lower lobes
   2. BWater collected from the stomach
   3. CSwabs from the nasal passages
   4. DMarrow from an intact femur
   Show answer and explanation

   Correct answer: D. Marrow from an intact femur

   Diatoms in the marrow of an intact long bone suggest they were carried by a working circulation after water was inhaled, which supports drowning when they match the diatoms in the water sample. Lungs, stomach and nasal passages can be contaminated by passive entry of water after death. The test still has false positives and negatives and must be read with other findings.

   Reference: Saukko and Knight, Knight's Forensic Pathology, 4th ed.

2. Question 2 · Firearm, Blast, Thermal and Electrical Injury

   A round gunshot wound on the back has a narrow, even rim of abraded skin around a central defect, with no soot or powder tattooing. What does the abraded rim most likely indicate?

   1. AThis is an exit wound
   2. BThis is an entry wound
   3. CThis is a contact wound
   4. DThis is a graze wound
   Show answer and explanation

   Correct answer: B. This is an entry wound

   An abrasion collar forms as the bullet indents and scrapes the skin edge when it enters, so it identifies an entry wound. Exit wounds are usually irregular and lack an abrasion collar unless the skin was supported against a firm surface (shored exit). The absence of soot and tattooing points to distant range rather than contact.

   Reference: DiMaio, Gunshot Wounds, 3rd ed.

3. Question 3 · Forensic Pathology Practice and Sudden Death

   At autopsy, a pathologist needs to decide whether a laceration was inflicted before or after death. Which finding most supports an antemortem injury?

   1. APostmortem CT, then open the heart under water
   2. BHaemorrhage with a cellular inflammatory response
   3. CAbsence of blood within the wound
   4. DPale, dry yellow wound margins
   Show answer and explanation

   Correct answer: B. Haemorrhage with a cellular inflammatory response

   Bleeding into surrounding tissue with an inflammatory cell response indicates a vital reaction, which requires a working circulation. Pale, dry, bloodless margins are typical of wounds inflicted after death. Gaping occurs in both antemortem and postmortem wounds because of skin elasticity.

   Reference: Saukko and Knight, Knight's Forensic Pathology, 4th ed.

4. Question 4 · Forensic Pathology Practice and Sudden Death

   A patient dies minutes after a central venous catheter is disconnected during transfer. Venous air embolism is suspected. Which approach best demonstrates air at autopsy?

   1. APostmortem CT before autopsy and opening the heart under water
   2. BRoutine autopsy with histology of the lungs and brain
   3. CDelay autopsy for 3 days to allow gas to accumulate
   4. DBlood cultures from the right ventricle at autopsy
   Show answer and explanation

   Correct answer: A. Postmortem CT before autopsy and opening the heart under water

   Air in the right heart is best shown by imaging before the body is opened and by opening the pericardial sac and heart under water to see bubbles escape. Delay increases putrefactive gas, which cannot be distinguished from embolic air. Routine dissection releases the air and loses the evidence.

   Reference: Saukko and Knight, Knight's Forensic Pathology, 4th ed.

5. Question 5 · Forensic Pathology Practice and Sudden Death

   A man dies 2 days after fractures of both femurs, with confusion, hypoxia and petechiae over the upper body. The pathologist wants to show fat embolism in the lungs. Which method is most appropriate?

   1. AHaematoxylin and eosin on paraffin sections
   2. BPeriodic acid-Schiff stain on paraffin sections
   3. CPerls Prussian blue stain on paraffin sections
   4. DOil Red O stain on frozen sections
   Show answer and explanation

   Correct answer: D. Oil Red O stain on frozen sections

   Routine paraffin processing dissolves fat, so lung tissue must be frozen and stained with a fat stain such as Oil Red O to show fat globules in capillaries. Haematoxylin and eosin on paraffin sections only shows empty vacuoles. Perls stain demonstrates iron, not lipid.

   Reference: Bancroft's Theory and Practice of Histological Techniques, 8th ed.

6. Question 6 · Forensic Toxicology

   A 70 kg man has a blood alcohol concentration of 1.0 g/kg at the time of interest. Using the Widmark formula with a distribution factor (r) of 0.7 and ignoring elimination, about how much alcohol is in his body?

   1. A35 g
   2. B70 g
   3. C100 g
   4. D49 g
   Show answer and explanation

   Correct answer: D. 49 g

   The Widmark formula gives the amount of alcohol in the body as A = C x r x W, so 1.0 g/kg x 0.7 x 70 kg = 49 g. Choosing 70 g ignores the distribution factor, which reflects that alcohol distributes in body water rather than total body mass. In practice, elimination since drinking must then be added back to estimate the amount consumed.

   Reference: Jones, Alcohol, its analysis in blood and breath for forensic purposes, Forensic Sci Rev