Introduction

Poisons have played a significant role in both accidental and intentional deaths throughout history. In forensic science, the study of poisons and their effects on the human body is known as Forensic Toxicology. Poison classification and detection are essential for determining the cause of poisoning, identifying toxic substances, and providing evidence in criminal investigations.

Definition of Poison

“Any substance that can cause harm, illness, or death when introduced into the body in sufficient quantity.”

The distinction between a poison and a drug is often dosage-dependent: many substances can be therapeutic at low doses and toxic at higher doses (e.g., Digitalis, Paracetamol).

Classification

1. Classification Based on Source
1.1 Plant Poisons

Toxic substances derived from plants. Many plants naturally produce poisons that affect the nervous system, heart, or digestive tract.

Poison	Source Plant	Mode of Action / Toxic Effect
Atropine / Hyoscyamine	Datura stramonium	Anticholinergic; causes hallucinations, tachycardia, dry mouth
Ricin	Ricinus communis	Inhibits protein synthesis; highly toxic
Coniine	Conium maculatum	Neurotoxin; causes respiratory paralysis
Digitalis glycosides	Digitalis purpurea	Cardiac poison; affects heart rate and rhythm
Aconitine	Aconitum species	Neurotoxin; causes cardiac arrhythmias and paralysis

1.2 Animal Poisons

Poisons produced by venomous animals or insects.

Poison	Source	Effect
Snake venom (Neurotoxin / Hemotoxin)	Snakes	Neurotoxicity or hemolysis depending on species
Scorpion venom	Scorpion	Neurotoxic; causes pain, convulsions
Tetrodotoxin	Puffer fish (Fugu)	Blocks sodium channels; causes paralysis
Bee / Wasp venom	Hymenoptera insects	Allergic reactions, anaphylaxis

1.3 Mineral Poisons

Toxic metals and inorganic compounds.

Poison	Source / Type	Toxic Effect
Arsenic	Arsenic salts, metalloid	GI irritation, multi-organ failure
Mercury	Mercury salts / elemental	Neurotoxin, nephrotoxin
Lead	Lead salts, old paint	Chronic poisoning; affects nervous system
Copper sulfate	Industrial / fungicide	GI irritation, hemolysis
Thallium	Rodenticides	Neurotoxic; alopecia; cardiac effects

1.4 Synthetic / Man-Made Poisons

Chemicals synthesized for industrial, agricultural, or domestic use.

Poison	Source	Effect
Organophosphates	Pesticides (malathion, parathion)	Acetylcholinesterase inhibitors; cholinergic crisis
Cyanides	Potassium cyanide, sodium cyanide	Blocks cellular respiration; rapid death
Carbon monoxide (CO)	Combustion gas	Binds hemoglobin; hypoxia
Methanol	Industrial solvent	Metabolic acidosis, blindness
Ethylene glycol	Antifreeze	Kidney failure; metabolic acidosis

2. Classification Based on Mode of Action

2.1 Corrosive Poisons

Destroy tissue on contact.
Common examples: Sulfuric acid, Nitric acid, Sodium hydroxide.
Effects: Burns, perforation of GI tract, vomiting.

2.2 Irritant Poisons

Cause inflammation or irritation.
Examples: Arsenic, Mercury, Pepper sprays.
Effects: Vomiting, diarrhea, pain.

2.3 Neurotoxic Poisons

Affect nervous system.
Examples: Strychnine, Cyanide, Aconitine.
Effects: Convulsions, paralysis, respiratory failure.

2.4 Asphyxiant Poisons

Interfere with oxygen transport.
Examples: Carbon monoxide, Hydrogen cyanide.
Effects: Hypoxia, brain damage, rapid death.

2.5 Cardiac Poisons

Affect heart and circulatory system.
Examples: Digitalis glycosides, Oleander.
Effects: Arrhythmias, cardiac arrest.

Routes of Poison Entry

Ingestion – Most common; food or drink contamination.
Inhalation – Toxic gases or fumes.
Injection – Snake bites, intravenous poisoning.
Absorption through skin – Pesticides, arsenic compounds.

Very Important Poisons Frequently Asked in UGC NET

Poison	Source	Type / Class	Mode of Action / Toxic Effect	Detection Method
Arsenic	Mineral (Arsenic salts)	Irritant / Systemic	Gastrointestinal irritation, multi-organ failure	Marsh test, AAS (Atomic Absorption Spectroscopy)
Mercury	Mineral (Hg salts, elemental)	Irritant / Neurotoxic	Neurotoxicity, nephrotoxicity	Reinsch test, AAS
Lead	Mineral (Pb salts)	Neurotoxic	Nervous system damage, anemia, kidney damage	AAS, blood lead levels
Cyanide	Synthetic (KCN, NaCN)	Asphyxiant	Blocks cellular respiration, rapid death	Prussian blue test, spectrophotometry
Carbon monoxide (CO)	Gas (combustion)	Asphyxiant	Binds hemoglobin → hypoxia	Spectrophotometry (COHb levels)
Organophosphates	Synthetic (pesticides)	Neurotoxic	Acetylcholinesterase inhibitor → cholinergic crisis	GC, HPLC
Strychnine	Plant (Strychnos nux-vomica)	Neurotoxic	CNS stimulant → convulsions, muscle rigidity	TLC, GC-MS
Atropine / Hyoscyamine	Plant (Datura stramonium)	Neurotoxic / Anticholinergic	Tachycardia, hallucinations, dry mouth	HPLC, TLC
Ricin	Plant (Ricinus communis)	Cytotoxin	Inhibits protein synthesis, highly toxic	ELISA, Mass Spectrometry
Digitalis glycosides	Plant (Digitalis purpurea)	Cardiac poison	Alters heart rate → arrhythmias	TLC, HPLC
Aconitine	Plant (Aconitum spp.)	Neurotoxic	Cardiac arrhythmias, paralysis	TLC, GC-MS
Coniine	Plant (Conium maculatum)	Neurotoxic	Respiratory paralysis	TLC, GC
Thallium	Mineral / Rodenticide	Neurotoxic	Alopecia, neuropathy, GI symptoms	AAS, ICP-MS
Methanol	Synthetic (industrial solvent)	Metabolic poison	Metabolic acidosis, blindness	GC, HPLC
Ethylene glycol	Synthetic (antifreeze)	Metabolic poison	Kidney failure, metabolic acidosis	GC, HPLC
Oleander toxins	Plant (Nerium oleander)	Cardiac poison	Arrhythmias, heart failure	TLC, HPLC
Tetrodotoxin	Animal (Puffer fish)	Neurotoxic	Blocks sodium channels → paralysis	GC-MS, ELISA
Snake venoms	Animal (elapids, vipers)	Neurotoxic / Hemotoxic	Neurotoxicity, hemolysis	ELISA, protein assays
Scorpion venom	Animal (scorpion)	Neurotoxic	Pain, convulsions, respiratory distress	ELISA, protein assays