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QUICK REVISION SHEET - WBUHS HIGH-YIELD PEARLS (Chapter 4)

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CHAPTER 4 - PRACTICE QUESTIONS

Missed & Underrepresented Topics (WBUHS Pattern)

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SECTION A: LONG ANSWER QUESTIONS (10-15 Marks)

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SECTION B: SHORT ANSWER QUESTIONS (5 Marks)

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SECTION C: SHORT NOTES (4 Marks)

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SECTION D: CASE-BASED VIGNETTES (Exam-Style)

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ANSWERS TO MISSED-TOPIC PRACTICE QUESTIONS

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Q1 - Answer

• Small (0.8 × 0.8 cm), round
• Inverted margins
• Abrasion collar present all around
• Hair singeing present (indicating secondary deposits from close/intermediate range)

• Large (2.5 × 2 cm), irregular
• Everted margins
• No abrasion collar
• Bullet exits and pushes skin outward

• Entry wound over right temporal region → if suicide, would expect the weapon to be accessible (temple is accessible, so suicide is possible)
• However: No soot/blackening inside wound track mentioned → not a contact wound
• In suicidal gunshot wounds, the weapon is usually in contact/very close → heavy blackening/soot in the wound
• Only singeing without blackening → the weapon was not in direct contact → range of several centimeters → inconsistent with typical suicidal self-inflicted range (which is usually contact/near-contact)
• Weapon not found at scene (as given in problem context) → further supports homicide

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Q2 - Answer

• Abrasion - superficial scraping of skin
• Contusion (Bruise) - bleeding into soft tissues without skin breach
• Laceration - tearing/splitting of skin by blunt force
• Fracture - break in continuity of bone

• Incised wound - clean cut, longer than deep
• Stab wound (punctured wound) - deeper than long
• Chop wound - caused by heavy sharp weapon (axe, dao)

• Gunshot wounds (entry, exit)
• Blast injuries

• Road traffic accident injuries
• Fall injuries

• Accelerating - force applied to stationary body
• Decelerating - moving body suddenly stops
• Compressive - crushing forces

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1. Full description of each wound - site, size, shape, edges, depth, floor, surrounding features
2. Nature of wound - to identify the type of weapon
3. Vital reaction - to confirm antemortem infliction
4. Age of wounds - to correlate with alleged time of assault
5. Direction and force - from abrasion trail, tailing, wound depth
6. Manner - homicidal, suicidal, or accidental
7. Cause of death - which injury was fatal
8. Defense wounds - indicate the victim's attempts to protect himself
9. Fabricated wounds - to detect false claims
10. Documentation - photographs, diagrams, measurements

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Q3 - Answer

• Falls from height (> own height)
• Falls at the same level (slip/trip)

• Accidental fall
• Suicidal leap
• Homicidal push

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1. Bilateral calcaneal (heel bone) fractures - primary impact point → feet struck the ground first; "Don Juan fractures" / "Lover's heel" - classic fall-from-height injury
2. Compression fractures of lumbar vertebrae - axial loading force transmitted from feet → ankle → tibia/fibula → knees → through pelvis → vertebral column → lumbar vertebrae compressed; "Burst fracture" pattern
3. Bilateral wrist fractures (Colles-type) - after the feet hit the ground, the body pitches forward → outstretched hands to break the fall → distal radius fractures (FOOSH - Fall On Out-Stretched Hand)
4. Splenic rupture - secondary impact as trunk decelerates rapidly; internal organs continue moving → shear forces → splenic avulsion/laceration

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Q4 - Answer

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1. Soot/carbon deposits in trachea, bronchi, lungs
2. Elevated carboxyhemoglobin in blood (> 15%)
3. Vital reaction in blisters

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• Flexion and adduction of arms
• Flexion of elbows and fists clenched
• Legs semiflexed

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Q5 - Answer

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1. Ligature mark: oblique, upward toward knot, pale, parchment-like, groove-shaped, incomplete circle
2. Face: pale (typical) or cyanosed if incomplete obstruction
3. Petechiae: may be present in eyes, face, scalp in atypical hanging
4. Tongue: may protrude between teeth
5. Eyes: open or closed; scleral congestion
6. Hands: may show clenching
7. Semen discharge (vaginal secretions in females): may occur

1. Neck dissection:

• Ligature mark groove visible in subcutaneous tissue
• Fracture/dislocation of upper cervical vertebrae (C2-C3) in judicial hanging - "hangman's fracture" of axis (odontoid process)
• In suicidal hanging: vertebral fracture rare; soft tissue injury more common
• Fracture of thyroid cartilage (occasionally)
• Tearing of intima of carotid artery (Simon's sign)
• Petechiae in neck muscles

1. Lungs: congested, may show edema
2. Brain: congested
3. Heart: right side distended with blood (dark)

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1. Indicator of asphyxia: Petechiae in the eyes (conjunctival/subconjunctival), face, and scalp are classic signs of mechanical asphyxia (strangulation, smothering, throttling, traumatic asphyxia)
2. Differentiating type of asphyxia:

• Profuse petechiae → strangulation/throttling (more obstruction to venous return)
• Fewer/absent petechiae → typical hanging (carotid/jugular compression with venous return partially maintained)

1. Evidence of cause of death: In a decomposed body, petechiae in the conjunctivae may be the only sign of asphyxial death
2. Age estimation: Fresh petechiae are bright red → become darker → cannot be used to age like bruises (subconjunctival haemorrhages do not undergo color changes - WBUHS pearl)
3. Tardieu's spots: Petechial haemorrhages on the lung surface, pericardium, and under the pleura; seen in asphyxial deaths; classic finding at autopsy

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Q6 - Answer: Defense Wounds

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• Location: Dorsum of forearms and hands (especially ulnar border), palms, fingers (palmar surface)
• Nature: Multiple incised wounds, stab wounds, or cuts on the arms
• The victim raises the arm to protect the face/neck → the assailant's knife/weapon strikes the arm

• Location: Forearms, hands, knees (crouching position)
• Nature: Contusions, lacerations, fractures (especially ulna fracture - "nightstick fracture" from blocking a blow)
• "Parry fracture" = fracture of the ulna from a defensive block

• Rare; the victim may raise the hand → bullet enters through the hand/arm

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1. Confirms homicide: Defense wounds prove the victim was conscious and alive at the time of attack, and that the attack was against the victim's will → confirms homicide (a person committing suicide does not defend themselves)
2. Direction of attack: The location and direction of defense wounds help reconstruct the direction from which the assailant attacked
3. Number of attackers: Multiple different directions of defense wounds may suggest multiple attackers
4. Nature of weapon: Incised defense wounds = sharp weapon; blunt defense wounds = blunt weapon
5. Victim's position: The location of defense wounds (e.g., dorsal forearm) suggests the victim had their arms raised in front of their face, indicating the attack was from the front
6. Corroborates witness statements

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Q8 - Contact Gunshot Wound to Head vs. Chest

1. Wound shape: Stellate/cruciform (star-shaped) - due to reflection of gases back from the bone (skull reflects the gas → gas tears the skin outward radially)
2. Blackening: Inside the wound track and on the undersurface of the scalp
3. Cherry-red colour: Tissues cherry-red from CO
4. Soot: Deposited deep within the wound track
5. Muzzle abrasion: The muzzle leaves an imprint/abrasion on the skin around the wound
6. Gas under scalp: Gases blow open the galeal space → stellate pattern
7. Internal: Skull base fracture common; brain surface shows soot; bursting fracture

1. Wound shape: Round or oval (soft tissue compresses; no underlying rigid bone to reflect gases)
2. Blackening: Inside the wound track; less stellate tearing (no rigid bone)
3. Muzzle abrasion: Present
4. No stellate tearing (unless very tight contact against a rib)
5. Gas: May cause pneumothorax by entering the pleural space
6. Air embolism: Possible if great vessels entered

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Q9 - Chopping Wound

1. Size: Large, often several centimeters long
2. Depth: Very deep - may cut through bone
3. Edges: Usually clean (sharp edge) but may be irregular at the corners
4. Associated bone injury: Characteristic - the bone is notched, split, or completely severed
5. Wound track: Wide and deep
6. Split/divided bones: Skull, ribs, or long bones may be split clean

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Q14 - Diffuse Axonal Injury (DAI)

1. Rapid deceleration/rotation → differential movement between grey and white matter (grey matter moves with skull; white matter axons lag behind)
2. Shearing forces stretch and tear axons throughout the brain
3. Most vulnerable areas: corpus callosum, internal capsule, brainstem (dorsolateral aspect), cerebral white matter
4. At cellular level: axonal retraction balls (microscopic hallmark) - swollen ends of torn axons visible within 12-18 hours

1. Immediate unconsciousness at the moment of impact (no lucid interval - this distinguishes from EDH)
2. Prolonged coma (days to weeks)
3. Decorticate/decerebrate posturing
4. CT may be initially NORMAL or show only small petechial haemorrhages (hence DAI is underdiagnosed on CT)
5. MRI (especially diffusion-weighted, gradient echo) better for diagnosis
6. Outcomes: persistent vegetative state, severe disability, or death

1. Road traffic accidents - major cause of severe TBI and disability after RTA
2. Shaken Baby Syndrome - a key mechanism; shaking causes rotational forces → DAI in infants; an infant with coma but no external head injuries should raise suspicion for shaken baby
3. Death certificate: Cause of death - diffuse axonal injury secondary to blunt head trauma
4. Disability claims: DAI can cause permanent disability without obvious CT findings
5. Normal CT with coma - DAI should be suspected; medicolegal implications for alleged negligence if CT-negative coma patient is discharged

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Q26 - Blast Injuries: Classification and Types

• Caused by the pressure wave (blast overpressure) itself
• Affects air-containing organs most severely: lungs, eardrums, bowel
• "Blast lung" = most common fatal primary blast injury: haemorrhage, oedema, alveolar disruption
• "Blast ear" = tympanic membrane rupture (barometric trauma)
• No external marks visible

• Caused by fragmentation (shrapnel, bomb casing, glass, debris propelled by blast)
• Penetrating injuries to any body part
• Most common type of blast injury in survivors

• Caused by the victim being thrown by the blast wind against hard surfaces
• Blunt force injuries from impact with ground, walls, etc.
• Head injuries, fractures, internal injuries

• All other injuries from the explosion: burns (flame, thermal), crush injuries (from falling structures), chemical/toxic exposure, psychological trauma (blast concussion)

• Quinary injuries (some classifications): Injuries from specific contamination (radioactive, biological, chemical agents in dirty bombs)

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Q27 - Primary and Secondary Projectiles in Blast

• Fragments of the explosive device itself (bomb casing, nails, screws intentionally packed into bomb)
• Travel at very high velocity (> 3000 m/sec for fragments from military explosives)
• Cause penetrating injuries

• Objects that are converted into missiles by the blast wave: glass, wood splinters, stones, metal objects, building materials
• Travel at lower velocity than primary fragments
• Still capable of causing serious penetrating injuries

1. Material from wounds can identify the type of explosive device
2. Fragment analysis (metallurgy) identifies bomb construction
3. Distribution pattern of injuries helps reconstruct position of victim relative to blast epicentre

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Q31 - Carbon Monoxide Poisoning Answer

• Most likely: Suicidal (deliberate enclosure in garage with engine running)
• Could be accidental (if fell asleep unknowingly)
• Homicide (if someone locked the person in) - rare

• Investigate scene (inside from = suicide; outside lock = homicide)
• Suicidal note
• History (depression, financial trouble)
• Toxicology (alcohol in blood)
• Position of body and vehicle controls

1. Cherry-red skin, mucous membranes, internal organs (due to carboxyhaemoglobin)
2. Blood is bright cherry-red/pink (carboxyhaemoglobin is bright red)
3. Brain: pink-red congestion; petechiae
4. Lungs: congested, pink-red colour
5. No soot in airways (CO is a gas, not particulate - unlike fire smoke)
6. Laboratory: Carboxyhaemoglobin level in blood (spectrophotometry)

• COHb 65% in this case = fatal concentration; consistent with death from CO poisoning

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RAPID REVISION: MISSED TOPIC MNEMONICS