Forensic Toxicology Practice Questions

Q: Aldrich-Mee's lines are characteristic of poisoning by which heavy metal?

Arsenic. **Explanation:** **Aldrich-Mee’s lines** (often simply called Mee’s lines) are transverse white bands or striae that appear across the fingernails and toenails. They are a classic sign of **Chronic Arsenic Poisoning**. **Why Arsenic is Correct:** Arsenic has a high affinity for sulfhydryl (-SH) groups found in keratin. During episodes of poisoning, arsenic is deposited in the nail matrix, disrupting normal keratinization. As the nail grows (approximately 0.1 mm per day), these white bands move distally. Because they are within the nail substance itself and not the vascular bed, the lines do not blanch under pressure and move outward as the nail grows. **Why Other Options are Incorrect:** * **Lead:** Characterized by the **Burtonian line** (a blue-purple line on the gums/gingival margin) and basophilic stippling of RBCs. * **Mercury:** Associated with **Pink disease (Acrodynia)** and "Mercurialentis" (discoloration of the lens), but not specific transverse nail lines. * **Copper:** Classically associated with the **Kayser-Fleischer (KF) ring** in the cornea (Wilson’s Disease) and "Green hair" in industrial exposure. **High-Yield Clinical Pearls for NEET-PG:** * **Raindrop Pigmentation:** Hyperpigmentation of the skin interspersed with small pale spots (leukoderma) seen in chronic arsenicosis. * **Hyperkeratosis:** Thickening of the skin on palms and soles is a hallmark of arsenic exposure. * **Specimen of Choice:** For chronic arsenic poisoning, **hair and nails** are the preferred samples because arsenic remains fixed in keratin long after it has cleared from blood and urine. * **Mnemonic:** "Mee's" lines = "Arsenic" (Both have 2 'e's or 's' sounds).

Q: What substance is commonly used in 'sin needles' for animal poisoning?

Rati seeds. **Explanation:** **Why Rati Seeds are Correct:** 'Sui' or 'Sin' needles are small, handmade spikes (1.5 to 2 cm long) prepared from the paste of **Rati seeds (*Abrus precatorius*)**. These seeds contain **Abrin**, a potent toxalbumin that inhibits protein synthesis (similar to Ricin). In veterinary forensic practice, these needles are surreptitiously driven into the hide of cattle to cause slow, agonizing death, usually for the purpose of skinning the animal for its hide. The needles are often disguised by being smeared with animal fat or cow dung. **Why Other Options are Incorrect:** * **Dhatura seeds:** These contain tropane alkaloids (Atropine, Hyoscine) and are primarily used as "stupefying agents" in road robberies or for accidental poisoning in children. They are not used to manufacture needles. * **Lead peroxide:** While used in the manufacture of matches and explosives, it has no role in the preparation of traditional 'sin' needles. * **Arsenic:** Although a common cattle poison (usually mixed with fodder), it is a chemical irritant and is not used to form solid mechanical needles like Rati paste. **High-Yield Clinical Pearls for NEET-PG:** * **Active Principle:** Abrin (one of the most lethal toxins known; more toxic than Ricin). * **Mechanism of Action:** Ribosome-inactivating protein (RIP) that halts protein synthesis. * **Clinical Presentation:** If injected (Sui), it causes local edema, necrosis, and painful swelling resembling **Malignant Edema or Anthrax**. * **Post-mortem Finding:** Fragment of the 'Sui' needle may be found at the site of injection. * **Fatal Dose:** 1–2 seeds (if chewed/crushed); **Fatal Period:** 3–5 days.

Q: What is the term for inhaling a drug using a cloth soaked in the substance?

Huffing. **Explanation:** Inhalant abuse (volatile substance misuse) involves the intentional inhalation of chemical vapors to achieve a psychoactive effect. The terminology is based on the specific method of delivery: * **Huffing (Correct Answer):** This refers to soaking a piece of cloth (like a rag or sock) with a liquid chemical (e.g., paint thinner, glue, or gasoline) and then holding the cloth over the mouth and nose to inhale the vapors. * **Bagging:** This involves spraying or pouring the substance into a plastic or paper bag and then inhaling the concentrated vapors from the bag. This method carries a higher risk of hypoxia and suffocation. * **Spraying:** This refers to spraying an aerosolized substance (like spray paint or deodorant) directly into the nose or mouth. * **Sniffing:** This is the simplest method, involving the direct inhalation of vapors from an open container (e.g., smelling a glue bottle or marker). **High-Yield Clinical Pearls for NEET-PG:** 1. **Sudden Sniffing Death Syndrome (SSDS):** The most feared complication of inhalant abuse. It occurs due to **catecholamine-induced ventricular arrhythmias**, as volatile solvents sensitize the myocardium to adrenaline. 2. **Glue Sniffer’s Rash:** An eczematous dermatitis found around the nose and mouth due to chronic contact with solvents. 3. **Common Agents:** Toluene (found in glue/thinner) is the most common solvent abused. Chronic toluene abuse can lead to **leukoencephalopathy** and renal tubular acidosis. 4. **Metabolic Marker:** Hippuric acid in urine is a marker for toluene exposure.

Q: What is the fatal dose of potassium cyanide?

200 mg. **Explanation:** **1. Why 200 mg is Correct:** Potassium cyanide (KCN) is a highly potent cellular toxin. The fatal dose for an average adult is typically cited between **200 mg to 300 mg** (or approximately 3 mg/kg body weight). It acts by inhibiting the enzyme **cytochrome oxidase**, which halts the electron transport chain in mitochondria, leading to "histotoxic hypoxia." Death occurs rapidly due to respiratory failure and cardiac arrest. **2. Why Incorrect Options are Wrong:** * **5 mg, 10 mg, and 20 mg (Options A, B, C):** These doses are significantly below the lethal threshold for humans. While cyanide is extremely toxic, the body has a limited capacity to detoxify small amounts via the enzyme **rhodanese**, which converts cyanide into the less toxic thiocyanate. These lower doses might cause symptoms of toxicity (dizziness, palpitations) but are generally not fatal. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Fatal Period:** Extremely rapid; death usually occurs within 5 to 15 minutes if ingested. * **Odor:** Characteristically described as **"Bitter Almonds"** (though ~20-40% of the population cannot smell it due to genetics). * **Post-Mortem Finding:** The most classic sign is **Bright Cherry Red** discoloration of the skin, mucous membranes, and blood (due to high oxyhemoglobin levels as tissues cannot utilize oxygen). * **Antidote (Cyanide Antidote Kit):** 1. **Amyl nitrite/Sodium nitrite:** Creates methemoglobinemia to bind cyanide. 2. **Sodium thiosulfate:** Provides sulfur to the rhodanese enzyme for detoxification. 3. **Hydroxocobalamin (Cyanokit):** The preferred modern antidote; it binds cyanide to form Vitamin B12 (cyanocobalamin).

Q: Marquis test is done for:

Morphine poisoning. **Explanation:** The **Marquis test** is a primary colorimetric screening test used in forensic toxicology to identify alkaloids, specifically **Opioids (Morphine and Heroin)**. The reagent consists of a mixture of formaldehyde and concentrated sulfuric acid. When added to a sample containing morphine, it produces a characteristic **deep violet/purple color** change, indicating a positive result. **Analysis of Options:** * **Morphine (Correct):** Morphine reacts with the Marquis reagent to form a purple color. It also gives a blue color with the Froehde’s test and a blue-green color with the Mecke’s test. * **Mercury (Incorrect):** Mercury is a heavy metal. Screening for mercury typically involves the **Reinsch test** (where a silver coating forms on a copper foil) or Atomic Absorption Spectroscopy. * **Arsenic (Incorrect):** Arsenic is also detected via the **Reinsch test** (forming a steel-grey deposit) or the **Marsh test** (forming a black "arsenic mirror"). * **Cyanide (Incorrect):** Cyanide poisoning is screened using the **Prussian Blue test** (forming a characteristic blue precipitate) or the Lee-Jones test. **High-Yield Clinical Pearls for NEET-PG:** * **Heroin vs. Morphine:** Marquis test turns purple for both, but heroin can be further differentiated by the nitric acid test (yellow to green). * **Dope Test:** Marquis reagent is frequently used in field kits by narcotics officers for rapid identification of seized drugs. * **Other Opioid Tests:** Remember **Husemann’s test** (Morphine + H₂SO₄ + HNO₃ → reddish-pink) and **Pellagri’s test** for morphine identification.

Question 1

Arsenophagists are:

Accepted Answer

Persons who can tolerate high doses of arsenic after taking arsenic in low doses at frequent intervals.

Answer

Criminals using arsenic for homicidal purposes.

Answer

Persons using arsenic as an abortifacient.

Answer

Persons using arsenic as a cattle poison.

Question 2

Aldrich-Mee's lines are characteristic of poisoning by which heavy metal?

Accepted Answer

Arsenic

Answer

Lead

Answer

Mercury

Answer

Copper

Question 3

What substance is commonly used in 'sin needles' for animal poisoning?

Accepted Answer

Rati seeds

Answer

Dhatura seeds

Answer

Lead peroxide

Answer

Arsenic

Question 4

What is the term for inhaling a drug using a cloth soaked in the substance?

Accepted Answer

Huffing

Answer

Bagging

Answer

Spraying

Answer

Sniffing

Question 5

What is the antidote for ethylene glycol poisoning?

Accepted Answer

Fluconazole

Answer

Methyl violet

Answer

Fomepizole

Answer

Ethyl alcohol

Question 6

What is the fatal dose of potassium cyanide?

Accepted Answer

200 mg

Answer

5 mg

Answer

10 mg

Answer

20 mg

Question 7

Which of the following is NOT an organophosphate insecticide?

Accepted Answer

Diazinon

Answer

Dieldrin

Answer

Fenthion

Answer

Propoxur

Question 8

Which drug is used for hypertension and pulmonary edema in the context of a scorpion sting?

Accepted Answer

Prazosin

Answer

Clonidine

Answer

Furosemide

Answer

Mannitol

Question 9

Which of the following statements about plant irritants is NOT true?

Accepted Answer

Abrus ingestion can mimic the clinical presentation of a cobra snake bite.

Answer

Nux vomica is a source of strychnine.

Answer

Sui-picking is a practice associated with Abrus precatorius.

Answer

Ricinus communis can produce symptoms similar to cholera.

Question 10

Marquis test is done for:

Accepted Answer

Morphine poisoning

Answer

Mercury poisoning

Answer

Arsenic poisoning

Answer

Cyanide poisoning

Forensic Toxicology — MCQs

Forensic Toxicology — MCQs

On this page

Practice by Chapter

Want unlimited practice?