FM2.17-19,FM3.1-4 | Asphyxial Deaths & Deaths from Physical Agents — Practice Quiz

In hanging the mark is oblique, above thyroid cartilage, and discontinuous at the knot site because the suspension force equals body weight acting upward.

Three differentiating features of hanging vs strangulation: direction (oblique vs horizontal), level (above vs at/below thyroid), and continuity (discontinuous at knot vs continuous).

Ligature strangulation produces a horizontal, continuous mark at or below thyroid cartilage level — the force is external, not gravitational.

Tardieu spots are petechial haemorrhages on pericardium and subpleural surface; they result from raised venous pressure and increased capillary fragility in asphyxia.

Asphyxia triad (hypoxia + hypercapnia + raised venous pressure) → Tardieu spots on pericardium and subpleural surface; also cyanosis, congestion, fluidity of blood.

Tardieu spots are specifically subpleural and pericardial, caused by the triad of hypoxia + hypercapnia + raised venous pressure — not a general visceral finding.

Manual strangulation: crescentic fingernail abrasions, fingerpad bruises on neck; hyoid fracture is a key finding especially in adults over 40 when bone is ossified.

Throttling = manual pressure on neck → fingernail marks, bruises, hyoid/thyroid fracture; ligature strangulation → horizontal groove; hanging → oblique groove.

A ligature furrow (oblique above thyroid) = hanging; horizontal furrow = ligature strangulation; petechiae alone are non-specific for type of asphyxia.

In freshwater drowning, diluted water passes from lung alveoli into blood → left heart chloride falls; right heart retains normal chloride. Left < Right.

Gettler's test: freshwater → Left Cl < Right Cl (dilution); saltwater → Left Cl > Right Cl (haemoconcentration). Wet drowning 85-90%; dry (laryngospasm) 10-15%.

In saltwater drowning, hypertonic water draws fluid out of blood → blood in left heart is haemoconcentrated → Left > Right. Freshwater = dilution effect = Left < Right.

Washerwoman's hands = maceration of palmar skin from prolonged water immersion (about 24-48 h); it is a postmortem change, not a vital reaction.

Distinguishing drowning signs: vital (froth, water in stomach, diatoms) vs. postmortem immersion (maceration, adipocere, loosened skin/hair).

Maceration is a decomposition/immersion change, not a vital reaction. Vital reactions in drowning include frothy fluid in airways, water-weed in hands, Gettler's test positivity.

Carboxyhaemoglobin > 30% in blood proves inhalation of smoke while alive — the most reliable indicator of vital reaction in fire deaths.

Vital reactions in burns: COHb > 30%, soot in airways/stomach, hyperaemia + blistering with serum fluid and PMN infiltration at burn margins.

Soot on skin/surface can be postmortem; boxer posture is heat-induced muscle contraction occurring postmortem; skin charring alone cannot confirm vitality.

Intense cyanosis is characteristic of asphyxial deaths, not cold deaths. Hypothermia shows paradoxical pink/red lividity due to preserved oxyhaemoglobin in cold-slowed circulation.

Hypothermia autopsy triad: pink lividity, Wischnewski spots, frost erythema (paradoxical undressing is ante-mortem behavioural sign).

Wischnewski spots (haemorrhagic erosions of gastric mucosa), pink lividity, and frost erythema are classic features of hypothermia. Cyanosis suggests anoxic/asphyxial cause.

Antemortem blisters contain serosanguinous fluid rich in protein and PMNs due to active inflammatory response — a vital reaction proving burns occurred before death.

Vital reaction in burns: antemortem blisters = serosanguinous fluid + protein + PMNs + hyperaemic base; postmortem blisters = clear/serous fluid, no cells.

Postmortem heat blisters contain clear or blood-tinged fluid without protein/cells; steam blisters from boiling water also lack PMN response.

Positional asphyxia: body posture (e.g., head-down, confined space) restricts chest expansion → ineffective breathing → death; common in intoxicated persons, vehicle accidents.

Types of mechanical asphyxia: hanging, strangulation, throttling, suffocation, choking, traumatic, positional, smothering. Each has distinct mechanism and signs.

Carotid compression = strangulation; foreign body in cords = choking (café coronary); water in alveoli = drowning. Positional asphyxia is purely mechanical restriction of respiration.

Starvation: all fat depots depleted; marrow fat replaced by gelatinous serous material (serous atrophy of marrow) — a pathognomonic finding of prolonged starvation.

Starvation autopsy: serous atrophy of fat and marrow, emaciation, small organs, brown atrophy of heart. Medico-legal: exclude natural disease; examine home environment, witnesses.

Tardieu spots = asphyxia; Wischnewski spots = hypothermia; COHb > 30% = fire/CO poisoning. Serous atrophy of fat + marrow is the hallmark of starvation deaths.

Diatoms in bone marrow/liver (reached via circulation during life) with matching species to recovery site = strong proof of antemortem drowning; postmortem submersion cannot transport them to marrow.

Diatom test: bone marrow or liver diatoms matching recovery site = antemortem drowning. Lung diatoms alone insufficient. Species match to water source strengthens conclusion.

Diatoms in lung alone insufficient (can enter postmortem). Marrow/liver diatom match is the gold standard. Diatoms exist in both freshwater and saltwater — species vary.

Judicial hanging uses a long drop — fracture-dislocation C2-C3 (hangman's fracture) with cord transection causes instantaneous death. Suicidal/homicidal hanging mainly causes asphyxia.

Mechanism of death in hanging varies by drop: long drop (judicial) = spinal cord transection; short drop = asphyxia + cerebral venous congestion; very short = carotid reflex.

Asphyxia + venous congestion = suicidal/accidental hanging (short drop); carotid sinus arrest = one mechanism in strangulation. Judicial = long drop = spinal mechanism.