Forensic Toxicology Practice Questions

Q: A family died in a closed room that was full of smoke from a wood fire. Which of the following findings is likely to be seen on the body?

A. Cherry red hypostasis. ***A. Cherry red hypostasis*** - Carbon monoxide (CO) from incomplete combustion of wood binds to hemoglobin with ~240 times greater affinity than oxygen, forming **carboxyhemoglobin (COHb)** - COHb has a characteristic **bright cherry-red or pink color**, which manifests as cherry-red hypostasis (post-mortem lividity) and pink coloration of internal organs - This is the **pathognomonic post-mortem finding** in CO poisoning deaths - Levels >50% COHb are typically fatal *B. Cyanosis* - Cyanosis (bluish discoloration) occurs when deoxygenated hemoglobin exceeds 5 g/dL - **Not seen in CO poisoning** because carboxyhemoglobin remains bright red, giving a pink appearance rather than blue - The victim may appear "healthy" or flushed despite being dead *C. Blackish discoloration* - Not a characteristic finding in CO poisoning - May be seen in putrefaction or certain chemical poisonings, but not acute CO exposure *D. Brown colored pigmentation* - Not associated with CO poisoning - Brown discoloration might suggest methemoglobinemia or post-mortem changes, but not CO toxicity

Q: A deceased woman was sent for an autopsy. She was found dead in a locked room with a heat stove still running. What is the most likely cause of death?

CO poisoning. ***CO poisoning***- The context of a deceased person in a locked room with a running heat stove points strongly to inhalation of **Carbon Monoxide (CO)**, a colorless, odorless gas produced by incomplete combustion.- CO has a very high affinity for **hemoglobin**, forming **carboxyhemoglobin**, which impairs oxygen transport and causes death via chemical **asphyxia**.*Cyanide poisoning*- Cyanide prevents cellular oxygen utilization (histotoxic hypoxia) by non-competitively inhibiting **cytochrome oxidase** in the mitochondria.- While highly fatal, cyanide is usually associated with the smell of **bitter almonds** at the scene and is not typically produced by household heat stoves.*H₂S poisoning*- **Hydrogen sulfide (H₂S)** poisoning is characterized by a distinctive odor of **rotten eggs** and is frequently associated with occupational exposure (e.g., sewers or drilling).- This gas also causes tissue hypoxia by inhibiting cellular respiration, but the circumstances described favor simple CO production from combustion.*Aluminium phosphide poisoning*- **Aluminium phosphide (ALP)** liberates **phosphine gas** upon exposure to moisture or stomach acid, leading to systemic toxicity.- This type of poisoning is usually due to deliberate ingestion of pesticides and causes severe effects, particularly on the **myocardium**, which is inconsistent with the presented scenario.

Q: In which poisoning is cherry red hypostasis seen on post-mortem examination?

CO Poisoning. ***CO Poisoning***- **Cherry red hypostasis** is the hallmark post-mortem finding in fatal **carbon monoxide (CO)** poisoning.- The bright red color is due to the formation of stable **carboxyhemoglobin (COHb)**, which retains this color even when blood pools after death.*Hydrogen sulphide* - Post-mortem findings usually include a **dark, tarry blood** consistency and the characteristic odor of **rotten eggs**.- It primarily acts by inhibiting cellular respiration, leading to asphyxia, but does not produce a bright red compound in the blood.*Yellow phosphorus*- This poisoning primarily causes severe **gastrointestinal irritation**, followed by fatal liver and kidney damage, leading to **jaundice**.- Post-mortem signs may include massive **hepatic necrosis** and luminescence (glowing) of the skin or vomit in the dark.*Hydrogen cyanide*- Cyanide poisoning can sometimes produce a pinkish flush or generalized redness but is typically associated with the odor of **bitter almonds**.- It causes cellular asphyxia by blocking **cytochrome c oxidase**, resulting in highly oxygenated venous blood (arterialization), but not the intense **cherry red** hue of CO poisoning.

Q: A 28-year-old male is brought to the emergency department unconscious after allegedly consuming an unknown substance. On examination, he has pin-point pupils, respiratory depression, and bradycardia. What is the most likely substance involved?

Opioid poisoning. ***Opioid poisoning*** - The classic triad of **opioid overdose** is altered mental status (unconsciousness/coma), **pin-point pupils (miosis)**, and profound **respiratory depression**. - Opioids depress the central respiratory drive and often cause **bradycardia** and hypotension due to central vagal stimulation. - This is the **most likely diagnosis** given the complete clinical picture. *Atropine poisoning* - Atropine causes **anticholinergic toxidrome** characterized by mydriasis (dilated pupils), **tachycardia**, hyperthermia, dry flushed skin, and urinary retention. - The presentation is opposite to what is seen here - this patient has **miosis and bradycardia**, not mydriasis and tachycardia. *Benzodiazepine overdose* - Benzodiazepine overdose causes significant CNS depression (sedation, coma) but typically maintains **normal respiratory function** when taken alone. - The pupils are usually mid-range or normal, and **pinpoint pupils** with marked respiratory depression and bradycardia are not characteristic features. *Organophosphate poisoning* - Organophosphate poisoning causes the **cholinergic toxidrome** (SLUDGE syndrome: Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis). - While it can cause **miosis and bradycardia**, patients typically also have excessive secretions, sweating, muscle fasciculations, and characteristic **garlic/petroleum odor**. - The absence of hypersecretion and fasciculations makes this less likely.

Q: One of the following statements regarding venom is incorrect:

Elapidae - Myotoxic. ***Elapidae - Myotoxic*** - This statement is **incorrect**. Venom from the **Elapidae** family (e.g., cobras, kraits, mambas) is **predominantly neurotoxic**, affecting the nervous system and causing paralysis. - The primary target of Elapidae venom is the **neuromuscular junction**, leading to respiratory failure, not muscle degeneration (myotoxicity). - While some Elapidae subspecies (certain sea snakes, Australian elapids) may have myotoxic components, the family is **classically characterized as neurotoxic**, especially in the Indian context where cobras and kraits are the main representatives. ***Common cobra - Neurotoxic*** - This statement is **correct**. The venom of the **Common Cobra** (Naja naja), which belongs to the Elapidae family, is highly **neurotoxic**. - It primarily contains long and short-chain neurotoxins that cause rapid, progressive **paralysis** and respiratory failure. ***Common krait - Neurotoxic*** - This statement is **correct**. **Common Krait** (Bungarus caeruleus), also an Elapid, possesses venom that is highly potent and entirely **neurotoxic**. - Krait venom often causes severe, often delayed, **neuromuscular blockade** and paralysis, making it one of the most dangerous snakes in India. ***Viperidae - Hemotoxic*** - This statement is **correct**. Venom from the **Viperidae** family (e.g., Russell's viper, saw-scaled viper) is mainly **hemotoxic** and **cytotoxic**. - It primarily targets the blood and vascular system, causing coagulopathy, massive tissue necrosis, bleeding disorders, and often **disseminated intravascular coagulation (DIC)**.

Q: In which of the following poisonings does silver nitrate impregnated filter paper turn black when exposed to gastric lavage contents?

Aluminium phosphide. ***Aluminium phosphide*** - Aluminium phosphide ($AlP$) reacts vigorously with water or gastric acid to release highly toxic **phosphine gas** ($PH_3$). - Phosphine gas is a strong reducing agent that reacts with **silver nitrate ($AgNO_3$)** impregnated paper, reducing it to black **metallic silver ($Ag$)** and thus turning the paper black, a method known as the field test for Celphos. ***Malathion*** - Malathion is an **organophosphate insecticide**, and its poisoning is diagnosed primarily by clinical features of cholinergic crisis (SLUDGE syndrome) and measuring depressed **serum/RBC cholinesterase levels**. - Organophosphates do not release phosphine gas and therefore do not produce a positive reaction with silver nitrate filter paper. ***Barbiturates*** - Barbiturate poisoning is confirmed using tests like the **Dille-Koppanyi test** (for color change) or advanced **chromatographic methods** on blood or urine samples. - The barbiturate structure does not produce a reducing gas like phosphine upon reaction, so the silver nitrate paper test would remain negative. ***Opium*** - Opium poisoning (due to alkaloids like **morphine**) is confirmed by detecting the drug or its metabolites in urine or blood using **immunoassays** or gas/liquid chromatography. - Opium alkaloids are not detected by this specific qualitative test, as it is designed to detect the highly reducing nature of phosphine gas.

Q: A patient is brought to the emergency department with acute onset of severe abdominal pain, throat irritation followed by vomiting that contains blood and bile, and diarrhea that initially appears bloody but later becomes colorless, odorless, and rice-water-like. On examination, a distinct garlicky odor is noted in the breath. Which of the following is the most likely agent responsible for the poisoning?

Arsenic. ***Arsenic*** - The combination of **acute severe gastroenteritis** (bloody, then "rice-water" diarrhea) and a distinct **garlicky odor** on the breath is pathognomonic for **acute arsenic poisoning**. - Arsenic is a potent cytotoxin causing widespread capillary damage, leading to severe fluid loss and shock, mimicking cholera. *Phosphorus* - **Phosphorus poisoning** typically presents with a **garlicky odor** (similar to arsenic) and severe gastroenteritis, but the characteristic diarrhea is often described as **smoky or luminous** in the dark, not the rice-water stools seen here. - The main toxicity is hepatotoxicity, leading to acute liver failure (jaundice, coagulation defects) in the second phase after an asymptomatic period. *Aluminium phosphide* - Poisoning from **aluminium phosphide** (often used as a rodenticide/fumigant, marketed as 'Celphos') produces a distinctive, strong odor of **phosphine gas**, usually described as **'rotten fish' or 'carbide'**, not garlicky. - Its main effect is **myocardial toxicity** and refractory hypotension. *Croton seeds* - **Croton seed poisoning** is characterized by intense localized irritation of the GI tract due to the toxin **crotin**, leading to severe **vomiting and purging** (diarrhea). - This poisoning **does not produce a garlicky odor** or the characteristic **rice-water stools** described in this presentation.

Q: All are causes of wrist drop (condition shown in the image below) except:

Zinc poisoning. ***Zinc poisoning*** - **Zinc poisoning** is not a characteristic cause of **wrist drop**, which is typically associated with **radial nerve palsy**. - While excessive zinc can cause copper deficiency and neurological issues, it does not directly lead to **radial nerve entrapment** or damage causing wrist drop. *Arsenic toxicity* - **Chronic arsenic poisoning** can lead to **peripheral neuropathy**, which may include motor weakness such as **wrist drop**. - The neurological damage is often dose-dependent and can affect various peripheral nerves. *Lead poisoning* - **Lead poisoning** is a well-known cause of **radial nerve palsy**, leading to **wrist drop**. - This is often seen in occupational exposures and can be quite specific to the **radial nerve**. *Use of crutches* - Prolonged or improper use of **crutches** can cause compression of the **radial nerve** in the axilla, leading to **crutch palsy**. - **Crutch palsy** manifests as weakness of the **forearm and hand extensors**, resulting in **wrist drop**.

Question 1

A family died in a closed room that was full of smoke from a wood fire. Which of the following findings is likely to be seen on the body?

Accepted Answer

A. Cherry red hypostasis

Answer

D. Brown colored pigmentation

Answer

B. Cyanosis

Answer

C. Blackish discoloration

Question 2

A deceased woman was sent for an autopsy. She was found dead in a locked room with a heat stove still running. What is the most likely cause of death?

Accepted Answer

CO poisoning

Answer

Cyanide poisoning

Answer

H₂S poisoning

Answer

Aluminium phosphide poisoning

Question 3

In which poisoning is cherry red hypostasis seen on post-mortem examination?

Accepted Answer

CO Poisoning

Answer

Hydrogen sulphide

Answer

Yellow phosphorus

Answer

Hydrogen cyanide

Question 4

A 28-year-old male is brought to the emergency department unconscious after allegedly consuming an unknown substance. On examination, he has pin-point pupils, respiratory depression, and bradycardia. What is the most likely substance involved?

Accepted Answer

Opioid poisoning

Answer

Atropine poisoning

Answer

Benzodiazepine overdose

Answer

Organophosphate poisoning

Question 5

One of the following statements regarding venom is incorrect:

Accepted Answer

Elapidae - Myotoxic

Answer

Viperidae - Hemotoxic

Answer

Common krait - Neurotoxic

Answer

Common cobra - Neurotoxic

Question 6

In which of the following poisonings does silver nitrate impregnated filter paper turn black when exposed to gastric lavage contents?

Accepted Answer

Aluminium phosphide

Answer

Malathion

Answer

Opium

Answer

Barbiturates

Question 7

In a suspected case of poisoning, gastric lavage fluid combined with silver nitrate solution gives rise to a black color in which poisoning?

Accepted Answer

Aluminium phosphide poisoning

Answer

Cocaine poisoning

Answer

Organophosphorus poisoning

Answer

Opium poisoning

Question 8

Match the following substances with their type of poisoning:
Substance:
A. Lead
B. Croton
C. Opium
D. Cocaine
Type of Poisoning:
1. Metallic irritant
2. Organic irritant
3. CNS depressant
4. Deliriant

Accepted Answer

A-1, B-2, C-3, D-4

Answer

A-2, B-1, C-3, D-4

Answer

A-4, B-3, C-2, D-1

Answer

A-3, B-4, C-1, D-2

Question 9

A patient is brought to the emergency department with acute onset of severe abdominal pain, throat irritation followed by vomiting that contains blood and bile, and diarrhea that initially appears bloody but later becomes colorless, odorless, and rice-water-like. On examination, a distinct garlicky odor is noted in the breath. Which of the following is the most likely agent responsible for the poisoning?

Accepted Answer

Arsenic

Answer

Aluminium phosphide

Answer

Phosphorus

Answer

Croton seeds

Question 10

All are causes of wrist drop (condition shown in the image below) except:

Accepted Answer

Zinc poisoning

Answer

Arsenic toxicity

Answer

Lead poisoning

Answer

Use of crutches

Forensic Toxicology — MCQs

Forensic Toxicology — MCQs

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