FPY1-3 Forensic Aspects of Asphyxia and Injuries

General Definition and Etiology of Asphyxia

• Etymological Origin: The term "asphyxia" is derived from the Greek language, translating to "lacking pulsation" or "pulselessness."

• Modern Forensic Definition: In contemporary forensic medicine, it is defined as a state of systemic hypoxia and cellular anoxia caused by the failure of cells to receive or utilize oxygen.

• Primary Causes of Oxygen Deprivation:

  • Insufficient oxygen present in the inhaled gas.

  • Mechanical blockage of airflow to the lungs.

  • Failure of oxygen transport to or utilization by cells (e.g., cases of carbon monoxide or cyanide poisoning).

Mechanisms and Categories of Mechanical Asphyxia

• Suffocation:

  • Specific Mechanisms: Smothering, choking, gagging, and confined space.

  • Pathological Focus: Internal or external blockage of the airway.

  • Common Manner of Death: Primarily accidental or homicidal.

• Strangulation:

  • Specific Mechanisms: Hanging, ligature strangulation, and manual strangulation (throttling).

  • Pathological Focus: Constriction of the neck and occlusion of blood vessels.

  • Common Manner of Death: Suicidal (specifically for hanging) or homicidal.

• Mechanical Asphyxia:

  • Specific Mechanisms: Traumatic, positional, and restraint asphyxia.

  • Pathological Focus: Compression of the chest or abdomen.

  • Common Manner of Death: Accidental or custodial.

• Drowning:

  • Specific Mechanisms: Wet drowning and dry drowning.

  • Pathological Focus: Inhalation of liquid or laryngospasm.

  • Common Manner of Death: Accidental or suicidal.

External Signs and Confined Space Asphyxia

• Diagnostic Physical Findings:

  • Congestion of the face accompanied by petechiae (pinpoint, round spots that appear on the skin as a result of bleeding) specifically in cases of strangulation.

  • Conjunctival petechiae (spots in the lining of the eyelids).

• Confined Space Hazards (Case Study: Sewer Workers):

  • Workers can die almost instantly in manholes due to asphyxiation caused by the displacement of oxygen by non-breathable gases.

  • Gases Involved: Carbon dioxide ($CO_2$) and methane ($CH_4$).

  • Toxic Gas Poisoning: Hydrogen Sulfide ($H_2S$). At high concentrations, $H_2S$ is lethal in a single breath.

Suffocation: Smothering and Airway Blockage

• Smothering:

  • Defined as the obstruction of the nose and mouth (often understood by laypeople as "suffocation").

  • Methods: Using hands, pillows, or plastic bags.

  • Risk Groups: Often seen in individuals with epilepsy or those under the influence of alcohol.

  • Autopsy Findings:

    • The presence of external trauma such as scratches, lacerations, or bruises on the lips or inside the cheeks suggests homicidal smothering.

    • The use of soft pillows may result in zero external pathology.

• Gagging:

  • Involves packing material such as cloth, tissue, or tape inside the mouth.

  • Mechanism: The gag pushes the soft palate upward and backward, sealing the nasal passages.

  • Complications: Gags soaked with body fluids may expand, becoming completely impermeable to air.

• Choking:

  • Defined as the occlusion of the internal respiratory tract between the pharynx and the bifurcation of the trachea by foreign bodies (e.g., food bolus, dentures, coins, or blood).

  • "Café Coronary" Syndrome: Instantaneous death due to sudden impaction of food in the throat. This triggers reflex vagus inhibition, leading to reflex neurogenic cardiac arrest.

Manual and Ligature Strangulation

• Manual Strangulation (Throttling):

  • Refers to the constriction of the neck using human hands, fingers, or forearms.

  • Occurrence: Almost always homicidal.

  • Neck Injury Patterns:

    1. Fingertip bruises (single or clusters of oval bruises).

    2. Fingernail abrasions.

  • Associated Finding: Significant facial congestion.

• Ligature Strangulation:

  • Occurrence: Usually homicidal, though occasionally accidental or suicidal.

  • Characteristics:

    • The ligature mark is typically horizontal (differing from the upward slant of hanging).

    • The ligature often encircles the entire neck.

    • The mark may show a "cross-over" pattern.

  • Case Study: Neck Hair-Thread Tourniquet Syndrome:

    • An accidental occurrence involving a toddler/infant. In one instance, a 21-month-old was entangled in his mother's long hair while co-sleeping.

    • The child appeared blue and unconscious but revived spontaneously. Examination showed a circumferential erythematous ligature mark on the neck with a visible crossing-over point.

Hanging

• Mechanism: Constriction around the neck is generated by the force of gravity acting on the body.

• Neck Mark Characteristics: Typically shows a component of upward slanting and is usually incomplete (does not encircle the neck entirely).

• Suspension Categories:

  • Complete Suspension: The body is hanging with feet entirely clear of the ground.

  • Incomplete Suspension: Parts of the body (toes, knees, or hips) remain in contact with a surface.

• Lethality and Force Requirements:

  • Venous occlusion of the neck requires only approximately $2\,kg$ of force.

  • Arterial collapse requires approximately $5\,kg$ of force.

  • Because of these low thresholds, incomplete suspension remains highly fatal.

• Common Manner: The majority of hangings are suicidal; accidental cases occur occasionally.

Traumatic and Sexual Asphyxia

• Traumatic Asphyxia:

  • Mechanism: Massive external weight acts upon the chest and abdomen, preventing the expansion of the thoracic cage and hindering normal respiratory excursions.

  • Scenarios: Building collapses, crowd stampedes/crush accidents, entrapment in industrial machinery or Road Traffic Accidents (RTA).

  • Physical Appearance: Striking, dramatic deep purple or red coloration of the head, neck, and upper chest area (specifically above the point of mechanical compression).

• Sexual Asphyxia:

  • Motivation: Partial asphyxia induces cerebral disturbances that may enhance sexual sensation.

  • Demographics: Usually involves young male adults.

  • Scene Characteristics: Unique setups often involving complicated combinations of ligatures and failed safety designs.

• Variations in Asphyxial Deaths:

  • Head enclosed in a plastic bag.

  • Electrical stimulation.

  • Glue-sniffing or volatile hydrocarbon substance abuse (e.g., inhaling liquid thinner inside a wardrobe).

Drowning

• Definition: Death resulting from the immersion of the nostrils and mouth in a liquid.

• Mechanisms of Death:

  • Dry Drowning: Cardiac arrest caused by the impact of cold water against the back of the pharynx and larynx.

  • Fresh Water Drowning.

  • Sea Water Drowning.

• Diagnostic Signs of Drowning:

  1. Presence of froth in the mouth and airway.

  2. Hyperinflated and waterlogged lungs.

Electrocution and Lightning

• Skin Resistance Values:

  • Moist and thin skin: $\sim 100\,\Omega$

  • Average skin: $\sim 1,000\,\Omega$

  • Dry and callous skin: $\sim 1,000,000\,\Omega$

• Electrical Marks:

  • High Voltage: Always produces electrical burns.

  • Low Voltage: May produce minor lesions or no discernible marks. Typical lesions include erythematous blistering or a lesion with a raised border and central crater, sometimes featuring charring.

  • Size: Usually small ($1$ to $1.5\,cm$ in diameter).

  • Locations: Found at entry and exit sites (commonly palms and feet).

• Lightning Injuries:

  • Blast Effects: Torn clothing and ruptured tympanic membranes with bleeding from the ear (may lead to suspicions of foul play).

  • Aborescent Marks: Unique fern-like or tree-like patterns on the skin.

  • Other Effects: Magnetization of metal objects, clothing catching fire, and potential for indoor strikes when using telephones or electrical appliances.

Burns, Scalds, and Explosion Injuries

• Fire/Flame Burns:

  • Most fire-related deaths are caused by the toxic effects of fumes rather than the burns themselves.

  • Major Contributions: Carbon monoxide poisoning ($CO$), Hydrogen Cyanide ($HCN$), and lack of oxygen.

  • Post-Mortem Findings: Soot in the airways and presence of carbon monoxide in the blood.

  • Murder Concealment: Murderers may set fire to a corpse, but internal organs often remain intact even if extremities are burned away.

• Contact Burns:

  • Caused by cigarettes, irons, or lighters.

  • Common in physical abuse cases involving children, domestic helpers, or spouses.

• Scalds (Wet Burns):

  • Usually superficial and moist, caused by hot water.

  • Patterns:

    • Splashes and droplets (e.g., oil on a forearm).

    • "Fluid level" marks, such as a "stocking distribution" seen when a child is dipped into a hot bath.

    • Fluid flow trails.

  • Effect of Clothing: Protects against minor scalds but prolongs contact and increases severity if the scalding is extensive.

• Explosion Injuries:

  1. Destruction/disarticulation if very near the blast.

  2. Flash burns or ordinary burns.

  3. Injuries from the wave of pressure.

  4. Impact from flying missiles/shrapnel propelled by the explosion.

  5. Crushing injuries from debris.

  6. Incapacitation or death by fumes.

  7. Visual Sign: Punctate lacerations and abrasions with "dust tattooing."