Forensic Toxicology and Chemical Analysis Questions and Answers

Answer: C

Potassium permanganate is used for gastric lavage in a strength of 1 : 5000.

Potassium permanganate is an oxidising agent. As a weak solution it oxidises poisons such as opium alkaloids, strychnine and phosphorus in the stomach, and toxicology texts give 1 in 5,000 as the standard strength for this use.

Strengths of 1 : 500 and 1 : 1500 are concentrated enough to be corrosive to the stomach lining; potassium permanganate crystals or strong solutions are themselves a cause of corrosive poisoning. 1 : 10,000 is weaker than the textbook strength.

Answer: B

Otto modified Stas's method for the removal of fat.

The Stas-Otto method is the classical toxicological extraction of alkaloids from viscera. Stas extracted the tissue with acidified alcohol; Otto's modification added an extraction of the acid solution with ether before it is made alkaline, which removes fats and other non-basic impurities, after which the free alkaloids are extracted from the alkaline solution.

Bone, tissue and water are not what the modification removes: the tissue is the starting material, and water is the extraction medium itself.

Answer: A

Chronic lead poisoning is called plumbism.

The name comes from the Latin plumbum, lead. Chronic lead poisoning, also called saturnism, causes a blue line on the gums (Burton's line), colic, anaemia with basophilic stippling of red cells, wrist drop and foot drop, and encephalopathy, especially in children.

The other terms belong to other conditions. Hydrargyrism is chronic mercury poisoning (from hydrargyrum), ptyalism is excessive salivation, a sign of mercury poisoning, and arsenicosis is chronic arsenic poisoning.

Answer: B

Crossing sativa with indica produced Skunk.

Skunk (Skunk #1) was bred in the 1970s by crossing Cannabis sativa and Cannabis indica strains, combining the fast growth and short flowering of indica with the potency of sativa. Its name comes from its strong smell, and 'skunk' became a general term for potent hybrid cannabis.

Sinsemilla means unpollinated female plants grown without seeds, a cultivation method rather than a cross. A clone is a cutting genetically identical to its parent, and the hop is a related plant of the same family, not a cannabis hybrid.

Answer: C

The correct matching is (a)-(ii), (b)-(iv), (c)-(i), (d)-(iii).

• Cardiac: Digitalis purpurea, the foxglove, source of digoxin and other cardiac glycosides (a-ii).
• Stimulant: Nicotiana tabacum, tobacco, whose nicotine stimulates nicotinic receptors (b-iv).
• Hallucinogen: Cannabis sativa, whose tetrahydrocannabinol alters perception (c-i).
• Depressant: Papaver somniferum, the opium poppy, source of morphine (d-iii).

The other options misplace these; option A, for example, makes cannabis a cardiac poison and tobacco a depressant.

Answer: C

The one that is not a date rape drug is nicotine.

Drugs used in drug-facilitated sexual assault are central nervous system depressants that act quickly, sedate the victim and cause amnesia, and are easy to slip into a drink. The classic examples are GHB (gamma-hydroxybutyrate), ketamine, a dissociative anaesthetic, and flunitrazepam (Rohypnol), a potent benzodiazepine.

Nicotine is a stimulant and does not produce sedation or amnesia, so it is not used as a date rape drug.

Answer: C

The correct matching is (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i).

• Allethrin (written 'Alethrin') is a synthetic pyrethroid, a pyrethrin-type insecticide (a-ii).
• Chlorthion is an organophosphorus insecticide (b-iii).
• Aldicarb is a carbamate insecticide (c-iv).
• Endrin is an organochlorine of the cyclodiene group, like aldrin and dieldrin (d-i).

Options A, B and D place one or more of these in the wrong chemical class, for example treating endrin as a carbamate or allethrin as an organochlorine.

Answer: B

A kerosene smell is characteristic of organophosphorus poisoning.

Organophosphorus insecticides such as parathion and malathion are usually sold dissolved in kerosene or other petroleum solvents. At autopsy, and in the breath and gastric contents of a patient, a kerosene-like smell is therefore a recognised clue to organophosphorus poisoning, along with pinpoint pupils and excessive secretions.

Cyanide gives a smell of bitter almonds, arsenic a garlic-like smell in some cases, and cannabis has its own characteristic odour, not that of kerosene.

Answer: C

The NPIC at AIIMS, New Delhi, was started in 1995.

The National Poisons Information Centre, in the Department of Pharmacology at AIIMS, was set up in 1995 by the Ministry of Health and Family Welfare. It gives round-the-clock information and advice on the diagnosis and treatment of poisoning to doctors and the public, and collects data on poisoning cases across India.

The other years, 1990, 1993 and 1998, are not the year the centre was started.

Answer: B

After 30 days the drug is most likely to be found in hair.

Drugs in the bloodstream are incorporated into the hair as it grows, at roughly 1 cm a month, and stay there. Hair therefore gives a long window of detection, months rather than days, and segmental analysis can even show roughly when the drug was used.

Blood and saliva detect most drugs only for hours to a day or two after use, and sweat, collected with patches, covers about a week of wear. A month after the crime, none of them would reliably show the drug.