Forensic Medicine & Toxicology
High-yield MBBS Forensic Medicine & Toxicology question bank — medical jurisprudence, identification, thanatology, injuries, asphyxia, forensic sexology and toxicology, at Reddy’s / Parikh depth.
12chapters144questions77High-Yield
Definition
A burn is injury caused by dry heat, flame, chemicals, electricity or radiation; a scald is caused by moist heat.
Types & Classification
- Dry heat — flame, radiant heat, hot solids; moist heat — scalds
- Chemical — corrosive acids and alkalis; electrical; radiation; friction burns
- Dupuytren’s classification — six degrees
- Wilson’s classification — epidermal, dermo-epidermal, deep
- Modern (clinical) — first, second (superficial and deep partial thickness), third degree (full thickness)
Degrees & Features
- First degree (epidermal) — erythema only; painful; heals without scar
- Second degree superficial — blisters (vesication), very painful, heals in 1–2 weeks with little scarring
- Second degree deep — whitish, less painful (nerve endings damaged), heals with scarring
- Third degree (full thickness) — charred, leathery, painless and insensitive, requires grafting; heals with contracture
- Severity depends on extent of body surface more than depth
Depth determines pain and scarring; extent determines survival. Degree Feature Healing First Erythema No scar Second Blisters Some scarring Third Charring, painless Grafting needed Applied
- Burns exceeding one-third of body surface are usually fatal
- In children and the elderly, smaller areas may prove fatal
🔑KEY POINTS TO REMEMBER- Burns are from dry heat; scalds from moist heat.
- First degree erythema, second degree blisters, third degree charring and painless.
- Prognosis depends more on surface area than on depth.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Distinguishing antemortem from postmortem burns establishes whether the victim was alive when the fire began.
Signs of Antemortem Burning
- Vital reaction — red line of hyperaemia at the margin of the burn
- Blisters containing fluid rich in albumin and chlorides, with a red inflamed base; postmortem blisters contain air and have a dry base
- Soot in the air passages — trachea, bronchi and beyond — proves the victim was breathing
- Carboxyhaemoglobin in the blood (raised COHb) — the most reliable proof of life during the fire
- Signs of inflammation and, if survival was longer, granulation tissue and infection
Cause of Death & Medicolegal Aspects
- Immediate — neurogenic shock, asphyxia from carbon monoxide and smoke inhalation, laryngeal oedema
- Early (days) — hypovolaemic shock from fluid loss, electrolyte imbalance, acute kidney injury
- Late — septicaemia (commonest late cause), Curling’s ulcer, pneumonia, ARDS, multiorgan failure
- Pugilistic attitude and heat haematoma are postmortem heat artefacts
- Manner: accidental (commonest), suicidal (self-immolation), homicidal (dowry death)
- Record a dying declaration after certifying the patient is compos mentis
Soot in the airways and raised COHb prove the victim was breathing. Feature Antemortem Postmortem Red line Present Absent Blister fluid Albumin, chlorides Air Soot in airway Present Absent Applied
- Always estimate carboxyhaemoglobin in fire deaths
- The pugilistic attitude must never be interpreted as a struggle
🔑KEY POINTS TO REMEMBER- Antemortem burns show a red line of hyperaemia and albumin-rich blisters.
- Soot in the airways and raised carboxyhaemoglobin prove life during the fire.
- Death from neurogenic shock, then hypovolaemia, then septicaemia.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Electrocution is injury or death caused by the passage of an electric current through the body.
Factors Determining Severity
- Type of current — alternating current (AC) is about 3–5 times more dangerous than direct current, as it causes tetanic muscle spasm preventing release
- Voltage and amperage — amperage kills; about 100 mA can cause ventricular fibrillation
- Resistance — wet skin greatly reduces resistance and increases danger; thick dry palms resist
- Duration of contact and path of current — hand-to-hand or hand-to-foot crossing the heart is most dangerous
- Earthing — essential for current flow
Findings & Mechanism of Death
- Joule burn (electric mark) — firm, raised, greyish-white, painless craterlike lesion with a pale raised margin at the entry point
- Metallisation — metal from the conductor deposited in skin; filigree (arborescent) burns
- Exit wound on the sole; skin splits resembling lacerations
- Death from ventricular fibrillation (low voltage), respiratory paralysis (medium), or brainstem paralysis and severe burns (high voltage)
- Delayed death from burns, kidney injury (myoglobinuria) and fractures from muscle spasm
- Manner: usually accidental; occasionally suicidal or homicidal
Alternating current locks the victim to the conductor, prolonging exposure. Voltage Mechanism of death Low Ventricular fibrillation Medium Respiratory paralysis High Brainstem paralysis, burns Applied
- The joule burn may be the only external finding — search hands and soles carefully
- Examine the scene and appliance; involve an electrical inspector
🔑KEY POINTS TO REMEMBER- AC is 3–5 times more dangerous than DC because of tetanic spasm.
- Joule burn is the characteristic painless craterlike entry lesion.
- Low voltage kills by ventricular fibrillation; high voltage by brainstem paralysis.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Lightning is a natural high-voltage electrical discharge causing injury or death, known as fulguration.
Mechanism of Injury
- Extremely high voltage (millions of volts) but very short duration (milliseconds), and direct current
- Direct strike — most fatal; side flash from a nearby object such as a tree
- Ground (step) current — travels through the earth; kills cattle and people standing nearby
- Flashover — current passes over the wet body surface, sometimes sparing internal organs
- Blast effect from the shock wave
Findings
- Lichtenberg figures (filigree, arborescent or fern-like marks) — reddish-brown branching pattern on the skin; pathognomonic but transient, fading within hours
- Magnetisation of metal objects carried by the victim; melted or fused metal (coins, jewellery, keys)
- Clothing torn or blown off, shoes burst open
- Singeing of hair, punctate burns, ruptured tympanic membranes
- Death from cardiac arrest (asystole) and respiratory arrest from brainstem paralysis
- Survivors may show keraunoparalysis — transient limb paralysis
The current is enormous but so brief that flashover may spare the body. Feature Detail Pathognomonic sign Lichtenberg figures Current Direct, very brief Metal Melted, magnetised Applied
- Photograph Lichtenberg figures immediately — they fade within hours
- Manner is always accidental; relevant to insurance claims
🔑KEY POINTS TO REMEMBER- Lightning is very high voltage direct current of extremely short duration.
- Lichtenberg (arborescent) figures are pathognomonic but fade quickly.
- Death from cardiac asystole and respiratory arrest; always accidental.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Extremes of heat, cold and deprivation of food produce characteristic systemic effects that may cause death.
Effects of Heat
- Heat cramps (miner’s cramps) — painful muscle spasm from salt loss; normal temperature
- Heat exhaustion — water and salt depletion; weakness, hypotension, sweating present
- Heat stroke (sunstroke) — failure of thermoregulation; temperature above 41–43°C, hot dry skin with absent sweating, delirium and coma; a medical emergency
- Heat hyperpyrexia; prickly heat
- Autopsy in heat stroke: non-specific — congestion, petechiae, rapid decomposition
Effects of Cold & Starvation
- Hypothermia — core temperature below 35°C; shivering, confusion, paradoxical undressing, bradycardia, coma
- Frostbite and trench (immersion) foot — local cold injury
- Autopsy in hypothermia: bright pink lividity, Wischnewsky spots (brownish gastric erosions), pancreatitis
- Starvation — acute (complete) or chronic (partial); death in about 6–8 weeks without food but with water; only 3–4 days without water
- Findings: gross emaciation, absent subcutaneous fat, atrophic organs, brown atrophy of the heart, gelatinous marrow
Both act by overwhelming the body’s temperature-regulating capacity. Condition Key sign Heat stroke Hot dry skin, >41°C Hypothermia Pink lividity, Wischnewsky spots Starvation Emaciation, brown atrophy Applied
- Bright pink lividity in hypothermia may be mistaken for carbon monoxide poisoning
- Starvation deaths raise questions of neglect or criminal negligence
🔑KEY POINTS TO REMEMBER- Heat stroke: temperature above 41°C with hot dry skin and absent sweating.
- Hypothermia below 35°C shows pink lividity and Wischnewsky spots.
- Death from starvation takes 6–8 weeks with water, 3–4 days without.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
A scald is an injury caused by moist heat — hot liquid, steam or hot vapour — in contact with the body.
Features
- Caused by boiling water, oil, steam, hot milk or molten metal
- Skin is sodden, bleached and soft; no charring or singeing of hair
- Blisters are common and prominent
- Lesions are superficial — usually first or second degree; deeper with oil or molten metal
- Trickle (splash) marks running downwards indicate the direction of flow and the position of the victim
- Steam causes more damage than water at the same temperature (latent heat)
Medicolegal Importance
- Manner: usually accidental, especially in children (pulling vessels of hot liquid)
- Immersion scald with a sharp ‘stocking and glove’ or ‘tide mark’ line and sparing of flexures suggests child abuse — forced immersion
- Homicidal scalding (acid or hot liquid throwing) occurs in domestic disputes
- Absence of splash marks with a uniform sharp margin favours deliberate immersion
- Cause of death and vital reactions assessed as for burns
Absence of singed hair is the simplest way to identify a scald. Feature Burn Scald Charring Present Absent Hair Singed Not singed Skin Dry, leathery Sodden, bleached Applied
- Sharply demarcated immersion scalds in a child suggest abuse
- Photograph splash and tide marks before dressing the wounds
🔑KEY POINTS TO REMEMBER- Scalds are caused by moist heat; skin is sodden with no charring or singed hair.
- Blisters and downward trickle marks are characteristic.
- Sharply demarcated glove-and-stocking scalds suggest deliberate immersion.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
The Rule of Nines (Wallace’s rule) is a rapid method of estimating the percentage of body surface area burnt.
The Rule in Adults
- Head and neck — 9%
- Each upper limb — 9% (total 18%)
- Front of trunk — 18%; back of trunk — 18%
- Each lower limb — 18% (total 36%)
- Perineum (genitalia) — 1%
- Total = 100%
Modifications & Use
- In children the head is proportionately larger — Lund and Browder chart is more accurate
- Infant: head 18%, each lower limb 14%
- Rule of palm — the patient’s own palm with fingers is about 1% — useful for scattered burns
- Guides fluid resuscitation (Parkland formula) and prognosis
- Burns over one-third of body surface are usually fatal; over 60% almost invariably so
- First-degree (erythema only) burns are not included in the calculation
The percentage burnt determines both fluid needs and survival prospects. Region Adult Infant Head and neck 9% 18% Each lower limb 18% 14% Trunk (front) 18% 18% Applied
- Use the Lund and Browder chart in children for accuracy
- Percentage burnt is recorded in the injury certificate and dying declaration
🔑KEY POINTS TO REMEMBER- Rule of Nines: head 9%, each arm 9%, each leg 18%, trunk 18% front and back, perineum 1%.
- Children need the Lund and Browder chart; the palm equals about 1%.
- Burns over one-third of body surface are usually fatal.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Heat stroke (sunstroke, thermic fever) is a life-threatening condition of failed thermoregulation with core temperature above 40–41°C.
Types & Pathophysiology
- Classical (non-exertional) — elderly, infants, chronically ill, during heat waves
- Exertional — young athletes, soldiers, labourers working in heat
- Failure of the hypothalamic thermoregulatory centre and of sweating
- Predisposed by high humidity, dehydration, alcohol, obesity, anticholinergic drugs, heavy clothing
- Leads to cellular damage, rhabdomyolysis, DIC and multiorgan failure
Features, Autopsy & Management
- Hot, dry skin with absent sweating — the cardinal sign
- Temperature above 41°C; delirium, convulsions, coma; tachycardia, hypotension
- Autopsy findings are non-specific — congestion, petechial haemorrhages, pulmonary oedema; rapid onset of rigor mortis and decomposition
- Diagnosis largely from circumstances and rectal temperature at the scene
- Management: rapid cooling (cold sponging, ice packs, immersion), fluids, treat complications
- Manner usually accidental; may raise questions of negligence in custody or labour
Once sweating fails, temperature rises uncontrollably. Feature Heat exhaustion Heat stroke Sweating Present Absent Temperature Normal/mild >41°C Consciousness Preserved Altered Applied
- Absent sweating with hot dry skin distinguishes it from heat exhaustion
- Record rectal temperature at the scene before cooling begins
🔑KEY POINTS TO REMEMBER- Heat stroke is thermoregulatory failure with core temperature above 41°C.
- Hot dry skin with absent sweating is the cardinal sign.
- Autopsy findings are non-specific; diagnosis rests on circumstances.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Hypothermia is a fall in core body temperature below 35°C, which may progress to death from cardiac arrest.
Causes & Clinical Stages
- Exposure to cold, immersion in cold water, high altitude, inadequate clothing
- Predisposed by extremes of age, alcohol, hypoglycaemia, hypothyroidism, malnutrition, immobility
- Mild (32–35°C) — shivering, confusion, tachycardia
- Moderate (28–32°C) — shivering ceases, bradycardia, paradoxical undressing, stupor
- Severe (<28°C) — coma, areflexia, ventricular fibrillation and asystole
- Osborn (J) wave on the ECG
Autopsy Findings & Importance
- Bright pink or cherry-red postmortem lividity — may be mistaken for carbon monoxide poisoning
- Wischnewsky spots — multiple small brownish-black gastric mucosal erosions (characteristic)
- Acute pancreatitis, fat necrosis, pulmonary oedema, frostbite of extremities
- Paradoxical undressing — body found undressed, may wrongly suggest a sexual assault
- Hide-and-die (terminal burrowing) behaviour — body found in a concealed place
- ‘Nobody is dead until warm and dead’ — rewarm fully before certifying death
Paradoxical undressing occurs when peripheral vasodilatation gives a false sense of warmth. Finding Significance Pink lividity Mimics CO poisoning Wischnewsky spots Characteristic Paradoxical undressing May mimic assault Applied
- Suspended animation may occur — never certify death in a cold body
- Estimate carboxyhaemoglobin to exclude carbon monoxide when lividity is pink
🔑KEY POINTS TO REMEMBER- Hypothermia is core temperature below 35°C.
- Autopsy shows pink lividity and Wischnewsky gastric spots.
- Paradoxical undressing may mimic sexual assault; rewarm before certifying death.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Starvation is the condition resulting from complete or partial deprivation of food, leading to progressive wasting and death.
Types & Survival
- Acute (complete) — total deprivation of food; chronic (partial) — inadequate intake over a long period
- Death in about 6–8 weeks without food but with water
- Only 3–4 days without water — water deprivation kills much faster
- Survival shortened by cold, exertion, disease, infancy and old age
- Body loses about 40–50% of weight before death; loss of 40% is usually fatal
- Order of tissue loss: fat first, then muscle; brain and heart are relatively spared
Autopsy Findings & Medicolegal Aspects
- Gross emaciation; skin dry, wrinkled, loose, earthy; sunken eyes
- Complete absence of subcutaneous fat; prominent bones
- Brown atrophy of the heart and liver (lipofuscin); gelatinous (serous) atrophy of bone marrow
- Stomach and intestines contracted and empty; gall bladder distended
- Anaemia, oedema (hypoproteinaemia), pressure sores, intercurrent infection
- Manner: accidental (famine, shipwreck), suicidal (hunger strike), homicidal (criminal neglect of infants, elderly or the helpless)
Death usually results from infection or cardiac failure, not hunger alone. Deprivation Survival Food only 6–8 weeks Food and water 10–12 days Water only 3–4 days Applied
- Criminal neglect of a dependent person is an offence — document carefully
- Exclude wasting diseases such as malignancy, tuberculosis and AIDS
🔑KEY POINTS TO REMEMBER- Death in 6–8 weeks without food but only 3–4 days without water.
- Findings: emaciation, absent subcutaneous fat, brown atrophy, gelatinous marrow.
- May be accidental, suicidal or homicidal through criminal neglect.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Dowry death is the death of a woman by burns or other unnatural cause within seven years of marriage in circumstances of dowry-related cruelty.
Legal Provisions
- Section 304-B IPC — dowry death: unnatural death of a woman within 7 years of marriage, shown to have been subjected to cruelty or harassment for dowry soon before death; punishable with imprisonment of not less than 7 years, extending to life
- Section 498-A IPC — cruelty by husband or his relatives
- Section 113-B Indian Evidence Act — presumption of dowry death — the burden shifts to the accused
- Dowry Prohibition Act, 1961
- Magistrate’s inquest is mandatory for any unnatural death of a woman within 7 years of marriage
Medical Officer’s Duties
- Record a dying declaration after certifying the patient is compos mentis; inform the Magistrate immediately
- Note the percentage and distribution of burns, presence of kerosene smell, singed hair
- Look for other injuries suggesting restraint, struggle or assault before burning
- Confirm antemortem burning — soot in airways, carboxyhaemoglobin, vital reaction
- Preserve viscera and clothing for chemical analysis (kerosene, poison)
- Autopsy by a board of doctors, videographed in many states
The law presumes dowry death, shifting the burden onto the accused. Provision Content 304-B IPC Dowry death 498-A IPC Cruelty 113-B Evidence Act Presumption Applied
- Always look for injuries other than burns — they may reveal homicide
- The dying declaration is often the single most important piece of evidence
🔑KEY POINTS TO REMEMBER- Dowry death: unnatural death of a woman within 7 years of marriage (Section 304-B IPC).
- Section 113-B Evidence Act raises a presumption against the accused.
- Requires magistrate’s inquest, board autopsy and a dying declaration.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.Definition
Frostbite is local tissue injury caused by freezing, chiefly affecting the exposed peripheral parts of the body.
Mechanism & Sites
- Tissue temperature falls below freezing → ice crystals form inside and between cells
- Vasoconstriction and thrombosis of small vessels cause ischaemic necrosis
- Damage worsens on rewarming (reperfusion injury)
- Sites: fingers, toes, ears, nose, cheeks and chin — exposed and poorly insulated parts
- Predisposed by wind chill, wet clothing, immobility, alcohol, smoking and peripheral vascular disease
Degrees & Related Conditions
- First degree (frostnip) — numbness, erythema, no tissue loss
- Second degree — clear blisters, oedema; superficial skin loss
- Third degree — haemorrhagic blisters, full-thickness skin necrosis
- Fourth degree — involvement of muscle and bone; gangrene and auto-amputation
- Trench (immersion) foot — prolonged exposure to cold and wet above freezing; chilblains (pernio) — mild recurrent cold injury
- Treatment: rapid rewarming in water at 40–42°C; avoid rubbing; delay amputation until demarcation
Vascular thrombosis, not the ice itself, causes most tissue loss. Degree Feature First Numbness, erythema Second Clear blisters Fourth Gangrene Applied
- Never rub frozen tissue — it worsens crystal damage
- Common in soldiers at high altitude and mountaineers
🔑KEY POINTS TO REMEMBER- Frostbite is local freezing injury with ice crystal formation and thrombosis.
- Affects fingers, toes, ears and nose; graded in four degrees.
- Treat by rapid rewarming at 40–42°C; never rub the tissue.
📚SOURCES: The Essentials of Forensic Medicine and Toxicology (K.S. Narayan Reddy); Textbook of Forensic Medicine and Toxicology (V.V. Pillay); Modi’s Textbook of Medical Jurisprudence and Toxicology.