Introduction and Scope of Forensic Toxicology

The discipline has a single founding text and a single founding case. The text is Mateo Jose Buenaventura Orfila's Traite des Poisons, published in two volumes in Paris in 1814 while Orfila was a 27-year-old Spanish-born chemist holding a medical chair at the University of Paris. Orfila dosed living dogs with controlled quantities of arsenic, antimony, mercury and the opium alkaloids, autopsied them, attempted to recover the poison from the viscera, and recorded both the symptom progression and the analytical residue. The Traite collected those experiments into a systematic toxicology accessible to judges, establishing Orfila as the acknowledged founder of forensic toxicology and giving French and continental practice a lead over the English-speaking world for much of the nineteenth century.

The founding case is the Marsh test. In 1832 the English chemist James Marsh was asked to test for arsenic in a poisoning trial, used the Scheele reagent of the time, and watched the colour fade between his bench and the courtroom; the accused was acquitted and Marsh spent the next four years building a better method. In 1836 he published the apparatus that still bears his name: zinc and sulphuric acid generate hydrogen, the suspect sample is added, any arsenic present forms arsine gas, the gas is decomposed on heated glass and deposits an unmistakable silvery-black mirror of metallic arsenic. The test was sensitive to roughly 0.02 milligrams and it became the first toxicological method that produced a stable, photograph-able physical record. The Lafarge trial in 1840, where Orfila himself testified using a Marsh apparatus, is the case usually cited as the moment forensic toxicology became courtroom practice.

The Indian thread joins the story late. The first chemical examiner's office opened in Madras in 1849 and in Calcutta in 1853, both staffed by British surgeons doing arsenic and opium work for the colonial courts. The Agra chemical examiner's office (now part of UP FSL) handled the Lakhimpur arsenic cases of the 1890s. CFSL Calcutta, the oldest of the central laboratories, traces its toxicology division to that lineage; CFSL Chandigarh and CFSL Hyderabad followed in the second half of the twentieth century, and FSL Sector 14 Madhuban in Haryana, which now handles most of the toxicology load from the National Capital Region, was set up in its current form in the 1990s.

Modern toxicology divides into four branches based not on the chemistry, which is shared, but on the question each branch is answering. The branches overlap at the bench: a senior toxicologist at AIIMS may handle a clinical case in the morning and a forensic case in the afternoon, but the four professional roles are distinct enough that most working analysts specialise in no more than two.

The clinical toxicologist works under time pressure measured in minutes; the antidote stocked at every district hospital pharmacy in Punjab (atropine, pralidoxime, naloxone, N-acetylcysteine) decides whether a poisoned farmer walks out at discharge. The analytical toxicologist works under method-development pressure measured in months and publishes in journals like Forensic Science International. The environmental and regulatory toxicologist works to FSSAI maximum residue limits and Bureau of Indian Standards drinking-water norms, with sample volumes large enough to be statistically representative of a population.

The forensic toxicologist works to a different constraint: the sample is whatever the autopsy surgeon collected (often 100 grams of liver and nothing more), the analyte is unknown at receipt, the timeline is the trial calendar of the local sessions court, and the answer has to survive a defence pleader's cross-examination two years later. Those four constraints together explain almost every procedural choice that follows in the rest of this module: why viscera are preserved in saturated salt, why a presumptive test never appears alone in the final report, why the LC-MS/MS run is duplicated, and why the analyst keeps a bench notebook countersigned page by page.

The boundary against pharmacology is sharp. A pharmacologist asks what a drug does at therapeutic dose in a healthy volunteer; a forensic toxicologist asks what the same drug, at five times the therapeutic dose, did to a 62-year-old with cirrhotic liver three days before death. The boundary against analytical chemistry is the matrix: a pure standard in methanol is an analytical-chemistry sample, the same drug in putrefied stomach contents from a Mumbai monsoon autopsy is a forensic one.

The job is roughly 20 percent instrumental analysis, 20 percent sample preparation, 30 percent paperwork, 20 percent report writing and court depositions, and 10 percent everything else (training junior analysts, ISO 17025 audits, calibration of the GC-MS oven). The instrumental fraction is the part the textbooks describe and is the smallest slice. The paperwork fraction (chain of custody verification, BNSS production-order replies, requisition triage) is the largest slice that nobody outside the lab sees.

1. Receipt and acceptance
   Sealed viscera arrive by police courier or post with a requisition from the investigating officer, a copy of the inquest panchnama and the autopsy surgeon's case sheet. The receiving clerk verifies seals, photographs them intact, and logs the case into the laboratory information system. A broken seal returns the case to the IO; in 2024 about 4 percent of viscera received at one north Indian SFSL were returned for that reason.
2. Case triage
   The bench toxicologist reads the inquest and autopsy notes. A cyanotic 24-year-old farmer with miosis, bradycardia and fasciculation points to organophosphate; a charred body in a Haryana wheatfield with hyperaemic mucosa points to aluminium phosphide; a Bihar cluster of blindness and acidosis points to methanol. Triage decides the first extraction and the first instrument.
3. Sample preparation
   Stomach contents are homogenised; liver is minced and macerated; blood and urine are aliquoted. Classical separation by Stas-Otto (acid and alkaline solvent partitioning) is still standard at most SFSLs for unknown organic poisons. Modern SPE cartridges and SPME fibres handle the cleaner cases at the central labs.
4. Presumptive screening
   Colour tests (Reinsch for heavy metals, Marquis for opioids, ferric chloride for salicylates, Trinder for paracetamol), TLC for alkaloid panels, and immunoassay kits for drugs of abuse give a first-pass triage. A positive screen never appears in the report on its own.
5. Confirmatory analysis
   GC-MS for volatile poisons (methanol, ethanol, organophosphate parent), LC-MS/MS for the drug panel and metabolites, ICP-MS or AAS for metals, ion chromatography for fluoride and oxalate. Quantitation runs against a calibration curve with a certified reference material; duplicate injection is standard.
6. Report and deposition
   The findings are written into a formal toxicology report under BSA Section 63, signed by the analyst and counter-signed where the SOP requires. The analyst is later summoned under BNSS to depose in person, with the original bench notebook available for the defence to inspect. A weak report is one a cross-examining lawyer can split apart in 20 minutes; a strong one survives a full day in the witness box.

The case mix in an Indian state FSL is heavily weighted toward rural self-poisoning. At FSL Sector 14 Madhuban (Haryana), aluminium phosphide and organophosphate cases together account for roughly half the toxicology workload in any given quarter; sedative overdose and alcohol-related deaths fill another quarter; the remaining quarter is the harder mix of drug-facilitated crime, dowry-burn cases with concealed sedation, suspected homicidal poisoning, and the occasional industrial cyanide or carbon monoxide death.

A forensic toxicology requisition in India may go to one of roughly seven kinds of laboratory, depending on the seizing agency, jurisdiction, case category, and prevailing workload. A district court in Andhra Pradesh sends viscera to the SFSL at Hyderabad or its regional unit at Vijayawada; a CBI case from Delhi goes to CFSL Chandigarh or CFSL New Delhi; an anti-doping sample from a national sports federation goes to NDTL at JLN Stadium; a suspected poisoning at AIIMS Delhi is worked up in-house by the Forensic Medicine and Toxicology department before any external referral.

• CFSL Chandigarh: the largest central forensic laboratory toxicology division, takes high-profile cases from across north India and runs the LC-MS/MS reference panel that smaller SFSLs send difficult cases to.
• CFSL Hyderabad: the southern equivalent, with strong work on aluminium phosphide and pesticide metabolites; also runs the narcotic drug reference function for southern states.
• CFSL New Delhi, Kolkata, Bhopal, Pune, Guwahati: the rest of the CFSL network under the Directorate of Forensic Science Services in MHA, each with a toxicology unit at varying capacity.
• FSL Sector 14 Madhuban (Haryana): handles Haryana and a large fraction of National Capital Region cases; one of the busiest toxicology benches in north India.
• State SFSLs: Mumbai Kalina (Maharashtra), Bangalore (Karnataka), Hyderabad SFSL (Telangana), Chennai (Tamil Nadu), Kolkata Belgachia (West Bengal), Lucknow Mahanagar (UP), Gandhinagar (Gujarat) and roughly 23 other state and regional units. Each state may have two to five regional FSLs feeding into the state headquarters.
• AIIMS Forensic Medicine and Toxicology, Delhi: hospital-based toxicology with clinical and forensic crossover; serves AIIMS autopsy load and acts as a reference body for difficult cases.
• NIMHANS Bangalore Centre for Forensic Analysis: specialised neurotoxicology, psychotropics and drugs of abuse with a reference role for southern states.
• NPIC at AIIMS Delhi (National Poisons Information Centre): the 24-hour clinical advisory service for treating physicians, not a forensic lab, but the source most accident-and-emergency teams call.
• NDTL (National Dope Testing Laboratory): WADA-accredited anti-doping lab handling sports samples; uses LC-MS/MS and isotope-ratio mass spectrometry. Separate from the forensic toxicology stream but the analytical state of the art.
• CDRI Lucknow and IICT Hyderabad: research institutions, not casework labs, but the methods that filter down to CFSL and SFSL benches usually originate here or at NFSU Gandhinagar.

At a north Indian SFSL, roughly the same six case patterns recur in varying proportions through the year. Recognising them is what triage depends on; the analytical approach follows from the pattern.

1. Rural pesticide self-poisoning: a 20-to-45-year-old farmer ingesting an organophosphate (chlorpyrifos, monocrotophos, profenofos) or aluminium phosphide tablet, presenting at the district hospital with cholinergic toxidrome or with fulminant cardiovascular collapse. ICMR Burden of Suicide work and NCRB Accidental Deaths and Suicides data both put pesticide ingestion among the leading single causes of suicide deaths in rural India, and the toxicology bench reflects that.
2. Alcohol under Section 185 Motor Vehicles Act: blood alcohol quantitation by headspace GC for drivers stopped at checkpoints in the National Capital Region, with the legal cut-off at 30 milligrams per 100 millilitres of blood. The case volume here is steady through the year and spikes around festivals.
3. Dowry-related deaths with concealed sedation: a young married woman found dead at home with burns, drowning or unexplained cause, with a toxicology question of whether benzodiazepines, zolpidem or an antihistamine sedative was administered before the act. The matrix is usually viscera with putrefactive change, and the LC-MS/MS confirmation is the key analytical step.
4. Urban polypharmacy and accidental overdose: an older patient on five-to-eight prescription drugs (often including warfarin, an opioid analgesic, a benzodiazepine and a tricyclic antidepressant) found dead at home with no scene evidence of foul play. The toxicology question is interaction-related rather than malicious.
5. Drug-facilitated crime: alleged spiking of food or drink with a sedative (benzodiazepines, zolpidem, gamma-hydroxybutyrate where available, or older antihistamines), often with a delayed sample collection that has already reduced the available analyte below the quantitation limit of GC-MS. Hair analysis at the central labs becomes the fallback.
6. Snakebite envenomation confirmation: a post-mortem from rural Maharashtra, Tamil Nadu or West Bengal with the question of whether a fatal collapse was envenomation from one of the Big Four (cobra, common krait, Russell's viper, saw-scaled viper) or an unrelated cause. Immunological ELISA confirmation on antemortem blood remains the gold standard where the sample exists.

The shape of the casebook varies by geography. A Punjab or Haryana bench is heavier on aluminium phosphide; a Kerala bench is heavier on Oduvanthalai (Cleistanthus collinus) plant poisoning and on prescription drug overdose; a Bihar bench periodically absorbs methanol cluster cases when bootlegged country liquor is contaminated, as in the Bihar tragedy of December 2022 where the casualty count exceeded 70 across Saran and Siwan districts. The chemistry across these patterns is shared, but the triage and the proportions are not.