Crime Scene Investigation in Poisoning Cases

A poisoning death rarely announces itself. The IO is summoned to a residence or a hospital ICU with a vague initial classification: sudden death, unnatural death, suspected suicide. The poisoning hypothesis usually emerges from one of a handful of physical signs that a trained first responder reads quickly.

Three scene patterns recur often enough that every IO who works rural and peri-urban India will see them inside the first year of posting.

• The bedroom with froth at the mouth. A working-age man, lying on a charpoy or bed, fine white froth at the corners of the mouth, an unmistakable petroleum or garlic odour in the room, sometimes a half-empty bottle of pesticide on the floor. This is the organophosphate signature. Monocrotophos, chlorpyrifos and quinalphos dominate the rural casebook across Maharashtra, Andhra Pradesh, Karnataka and Tamil Nadu.
• The unconscious patient with an empty Celphos foil. Brought to the casualty ICU, hypotensive, refractory to fluids, with a metallic-fishy or garlic smell on the breath. A crushed silver-coloured foil of aluminium phosphide is recovered from the patient's clothing or from the family member who accompanied them. This is the Punjab and Haryana pattern, and the lethality is so high that the ante-mortem gastric lavage is often the only sample with intact phosphide for FSL confirmation.
• The body slumped over a dinner plate. Less common, but the signature of the homicidal-poisoning hypothesis. Food on the plate, a glass of water or buttermilk to one side, sometimes prasad from a temple visit earlier in the day. The IO collects everything on and around the plate, because the toxicology bench cannot guess which one carried the dose.

Each of these tells the IO which samples to prioritise and which physical risks the responding team needs to manage before disturbing anything. The chain of custody starts here, not at the malkhana. The first photograph the IO takes is already an exhibit. The first conversation with the family is already a witness statement in the making. How the scene is handled in the first ten minutes determines the evidentiary record the case is built on.

1. Secure the scene and summon witnesses
   Cordon the room. Note who was present on arrival, who left and when. Summon two independent panch witnesses for the search and inquest. Under BNSS Section 105, the search itself is recorded on audio-video where practicable; the recording is part of the case file the FSL and the trial court will see.
2. Photograph everything in situ
   Wide shot of the room, mid-shots of the body and the immediate surroundings, close-ups of the mouth, the hands, any container, foil or note within reach. Photograph before anything is moved. The photographs anchor every later sample to a position in the room.
3. Call the medical officer for inquest
   BNSS Sections 175 and 176 replace the old CrPC 174 inquest. The medical officer records the apparent cause and the visible signs. For a suspected poisoning, the inquest panchnama lists vomitus, foil, food and any container the IO intends to seize.
4. Collect the biological samples first
   Vomitus on floor and bedding into a wide-mouthed glass jar, topped with saturated NaCl. Any gastric lavage that the hospital has retained. Clothing showing vomit, urine or faeces staining, each garment in its own paper bag (never polythene for biological matter). Hair, where chronic poisoning is suspected.
5. Collect the chemical and food samples
   The half-eaten plate, the glass with residue, the milk packet, the water bottle, the tiffin, the prasad. Empty foils and blister packs, prescription containers, the steel tumbler with the unknown liquid. Any white powder on a surface, lifted with a clean spatula into a screw-cap glass vial. Pesticide containers from the field or the godown if they appear linked.
6. Seal, label, sign and forward
   Each container into its outer packet, tied, wax-sealed under the IO's personal seal, co-signed by panch witnesses and the medical officer. Form 65 BNSS forwarding memo completed. Sealed packets dispatched to the relevant FSL within 48 to 72 hours.

Departures from this sequence, photographing after the body has been moved, signing the seizure list before the panchas arrive, or combining samples into a single jar, frequently appear as the central challenge in defence appeals. A procedural defect at the scene cannot be corrected by the analytical result in court.

The toxicology bench can only analyse what arrives in a recognisable, intact form. The IO's job is to put each suspect material into the right container with the right preservative, and to keep food samples separate from biological samples, and biological samples separate from each other.

The standard scene sample list for a suspected poisoning, in the order it tends to be collected:

• Vomitus. From the floor, the bedding or the bowl the family used. Lifted with a clean spatula into a wide-mouthed glass jar, half to two-thirds full, topped with saturated sodium chloride. One sample per location; if there is vomitus on the floor and separately on the pillow, that is two jars, not one.
• Gastric lavage fluid. From the casualty ICU, if the patient was washed out. This is often the only ante-mortem sample where phosphide, paraquat or organophosphate is still present at meaningful concentration, and the hospital must be asked to retain it the moment poisoning is suspected.
• Food and drink. Every plate, every glass, every container that the family or witnesses connect to the meal. Half-eaten chapati and dal into separate jars. Glass with residue, sealed as is. The milk packet, the water bottle, the tiffin from the workplace. Where the death follows a religious gathering, prasad is its own evidentiary item.
• Prescription containers and foils. Empty blister packs, half-finished sedative bottles, the silver Celphos foils with the faint garlic odour, OP pesticide bottles from the agricultural shed. The label is part of the evidence; do not strip it.
• Suicide note. Where present, photographed in situ, then placed in a paper envelope with the IO's seal. The note's evidentiary chain runs alongside the toxicological chain.
• Hair. Where chronic poisoning is suspected (arsenic in long-running domestic cases, thallium in academic and workplace cases), a pencil-thick lock from the posterior vertex, cut close to the scalp, root end clearly marked. Segmental analysis at the lab can date the exposure.
• Stomach lavage tubes and IV lines. Where the patient was hospital-managed, the tubing itself may carry residue. The hospital retains them on the IO's written request.
• Scene swabs. For the white powder on the kitchen counter, for the dried liquid in the steel tumbler, for the suspected residue on the body's clothing. Sterile cotton swabs into screw-cap vials, dry. Do not pre-wet with saline.
• Garments. Showing vomit, faeces, urine, or any liquid residue. Each garment in its own paper bag, fully air-dried before sealing if damp.
• Pesticide containers. From the field, the godown, the shed, the bag the deceased was carrying. The container, the cap and any residue inside go together.

The single most preventable mistake at a poisoning scene is the wrong preservative. Formalin destroys most analytes the toxicology bench wants to look at. Polythene degrades volatile poisons. A glass jar with an ill-fitting cork lets phosphine escape on the way to Madhuban.

The labelling on every container is what links it to the case. The standard label carries: case number, FIR number, police station, date and time of collection, IO name, sample description, weight or volume of sample, and signatures of IO, panchas and (where present) the medical officer. Each label is on the container, not on the outer packet, because the outer is often discarded at the FSL intake.

The outer packaging itself is its own document. A wide-mouthed glass jar with a screw cap, wrapped in a clean cloth or paper, tied with thread in a way that crosses the cap, sealed with melted wax at the knot, and impressed with the IO's personal seal. The seal impression is captured on the Form 65 BNSS forwarding memo at the time of sealing, not later. The packet is then cushioned with thermocol or cotton in a cardboard outer for transport.

Sealed packets travel from the police station malkhana to the FSL by official courier or by an authorised constable, accompanied by the Form 65 BNSS forwarding memo and the relevant FSL form annexures. The dispatch window most state FSLs work to is 48 to 72 hours from seizure. Anything longer becomes a chain-of-custody gap the defence will press.

State workflows vary in routing but converge on the documentation. A poisoning case from rural Sonipat goes to FSL Sector 14 Madhuban in Haryana. A case from Mumbai's western suburbs goes to FSL Kalina. A Chandigarh case lands at CFSL Sector 36. A Hyderabad city case goes to FSL Rasayan Bhavan at Red Hills. Each of those labs has its own intake form, its own malkhana register and its own deposit-slip format, and the IO is expected to know the local version.

Once the FSL completes the analysis, the report is forwarded to the IO under cover of a certificate. Under BSA Section 63, the certificate is what makes the FSL's electronically generated report admissible at trial. The certificate identifies the device, the analyst, the date range of the analysis and the integrity of the record. The chain of custody documentation accompanies the certificate; if the chain is broken at any link, the certificate cannot rescue the report.

The leading authority on the certificate requirement is Arjun Panditrao Khotkar v Kailash Kushanrao Gorantyal (2020), decided by a three-judge bench of the Supreme Court. Khotkar held that the Section 65B certificate (now Section 63 BSA) is a mandatory pre-condition to admissibility of electronic records, and that oral testimony of the analyst cannot substitute for the certificate. For toxicology, that means the FSL report, the chromatogram, the mass spectrum and the worksheet are admissible only if the BSA 63 certificate travels with them. An analyst stepping into the witness box without the certificate cannot fix the omission from the box.

The other provision the IO and the FSL need to know is BNSS Section 349, which governs the production of an expert witness. The defence is entitled to call the analyst and to cross-examine on the worksheet, the calibration record and the chain. An IO who has prepared a clean chain has very little to defend at this point; an IO who took a shortcut on the wax seal faces a procedural challenge the analytical result cannot rescue.

The same handful of mistakes appears in the appellate record over and over. None of them are mysterious; all of them are preventable at the scene.

• Formalin in the viscera jar. Destroys alkaloids, OPs, alcohols, phosphides and many drugs. Saturated NaCl is the standard, and "we ran out of NaCl so we used formalin" is the loss-condition for the case.
• One jar for multiple organs. Stomach, intestine and liver in the same container destroys the spatial information the toxicologist uses to confirm ingestion versus dermal or inhalation exposure. The one-jar-per-organ rule is not optional.
• No panch witnesses at the seizure. A seizure memo without two independent panchas is a memo the defence will argue should not have been admitted. BNSS 105 audio-video recording mitigates this but does not replace the panchas.
• No photographs before disturbance. Photographs taken after the body was moved cannot anchor sample positions. The room is photographed before the medical officer arrives, not after.
• No wax seal under personal seal. A sealed packet without a wax impression that matches the seal on the forwarding memo is the textbook broken-chain attack. Ashish Jain reasoning applies directly: independent of the analytical result, the procedural defect is fatal.