Crime Scene Investigation in Poisoning Cases

Initial information may describe collapse, illness, an unexplained death or several people affected in one location. Establish whether anyone needs immediate assistance and whether a hazardous atmosphere, spill or reactive substance may be present. Restrict access and obtain specialist response when the situation exceeds the team's training or equipment.

Do not approach an unknown chemical by smelling, tasting or casually opening its container. Some substances have poor odour-warning properties, and absence of smell does not establish safety. Metallic phosphides can release phosphine on contact with moisture, including from contaminated material. Handling and transport require hazard-specific advice.

Respiratory protection must match the hazard and response plan. An ordinary mask is not protection against an oxygen-deficient or unknown dangerous atmosphere. Entry, atmospheric monitoring, ventilation and decontamination decisions belong to appropriately trained personnel under the incident arrangements.

Record initial observations without naming an unconfirmed poison. Froth, small pupils, a liquid residue or an agricultural container may help develop a hypothesis, but none is a unique signature. Several diseases, injuries, exposures and interventions can produce similar appearances.

Establish a controlled scene boundary and record who enters, why and when. Information from responders and witnesses can explain changes made before the examination, including resuscitation, ventilation or removal of a person. These necessary actions should be documented rather than described as automatically destroying the case.

A walkthrough identifies relevant locations, items, hazards and transient evidence before detailed recovery, where safety allows. Document the scene as found through notes, photographs, sketches or other appropriate records. Include the relationships between a person, containers, food, medicines, equipment and residues.

Use overall, intermediate and close views as appropriate, keeping a clear link between each exhibit and its original position. An image of a bottle alone may lose the context that made it relevant. Record whether caps were attached, whether packaging was open and whether residues appeared in more than one location.

Develop a collection plan around competing explanations. A medicine container can support prescribed use, accidental ingestion or deliberate administration; it may also be unrelated. Relevant treatment records, witness accounts and product examinations help distinguish these possibilities without fixing the conclusion in advance.

Prioritise material at risk of change or loss and consult the laboratory about unusual targets. Avoid unnecessary destructive field tests on limited specimens. Where several disciplines need the same item, plan their sequence so that one examination does not consume or contaminate evidence needed by another.

Document the reason for material not collected, delayed collection or a departure from the intended sequence. Good documentation supports assessment of an actual limitation. A rigid claim that every change in sequence makes evidence inadmissible is scientifically and legally unjustified.

Collection depends on the hypothesis, authority and laboratory advice rather than a universal ten-item kit. Distinguish scene material from clinical or post-mortem specimens: an investigator does not perform an invasive medical collection merely because it appears in a scene checklist.

Food, drink and residues may help investigate a possible source. Keep distinct items or locations separately identified. A container label, batch number, remaining contents and cap can be relevant, but a label is not analytical confirmation of the contents or their concentration.

Vomitus or retained clinical material may contain useful evidence, but treatment and contamination must be considered. Gastric lavage should never be performed merely to obtain a forensic specimen. If it was clinically undertaken, record added fluids, medicines, collection time and handling so the laboratory knows that the matrix has been altered.

Comparison samples and collection blanks can help assess background or contamination when appropriate. Their location and collection method must be justified; a single arbitrary distance from a spill does not guarantee an uncontaminated control. Coordinate this part of the sampling plan with the laboratory.

Hair may assist selected exposure investigations but is not a universal substitute for blood or urine. External contamination and growth variability complicate interpretation, and segmental results cannot precisely date every exposure. Hair collection belongs to a target-specific plan, with authority and orientation documented.

The target and matrix determine packaging. A volatile analyte may require a tightly sealed compatible container and controlled storage; a trace-metal investigation requires attention to container background. Reactive residues can need specialist dangerous-goods handling. Do not improvise a universal double-sealed jar for every hazardous chemical.

Saturated salt solution is used in some regional tissue-collection practices, but it is not a universal preservative for vomitus, food, urine or viscera. Adding any preservative changes the matrix and can interfere with a target or method. Follow the receiving laboratory's validated instructions and record what was added.

Routine formalin fixation is unsuitable for specimens intended for many toxicology methods. Keep separately collected material for histology and toxicology when required. Avoid the equally inaccurate claim that formalin destroys every analyte or that a fixed specimen can never be examined; specialised assessment may still identify limited options.

Do not automatically rinse tissues, dry chemically contaminated garments or leave volatile evidence exposed. Such steps can remove, redistribute or lose the target. Biological-evidence drying guidance must not be applied blindly where toxicology, volatile chemicals or responder hazards require different handling.

Each primary container should remain independently identifiable. Record a unique item or specimen identifier, description, original location or anatomical site, collector, collection date and time, and relevant preservative. Include known hazards and any uncertainty about the source. Record measured quantity only where it was actually measured.

Use tamper-evident sealing and appropriate secondary containment according to the service's procedures. The seal method is not universally melted wax. The transport package should preserve both the specimen and the safety of handlers, with required hazard declarations and temperature arrangements.

Custody records connect collection, storage, transfers, laboratory receipt and subsequent handling. Record identities, dates, times, purposes and relevant condition checks. At receipt, the laboratory should assess seals, labels, leakage, specimen suitability and discrepancies before testing.

Dispatch promptly under analyte-appropriate conditions. There is no universal 48–72-hour interval that guarantees stability or automatically breaks the evidential chain. A short undocumented interval can matter; a longer well-documented interval may preserve identity while still creating an analyte-stability concern. Evaluate these issues separately.

The submission should state the question, requested tests, scene and clinical information, treatment, collection details and known hazards. Missing history can make a negative result misleading if the laboratory did not test for the relevant target. Communicate changes in the investigation rather than assuming a broad screen covers everything.

Digital photographs, recordings, chromatographic data and electronic reports need their own integrity and provenance records. Those records do not replace custody of the physical specimen. Equally, an intact specimen seal does not establish that every electronic file is authentic or complete.

Search powers, witness requirements, report procedures, disclosure and electronic-record rules depend on the actual jurisdiction and proceeding. Do not describe a national electronic-record certificate as an automatic cure for a physical-custody gap, or claim every toxicology report worldwide requires the same form.

A discrepancy should be documented, investigated and reported according to its possible effect. Neither concealed irregularities nor blanket promises of a guaranteed courtroom result serve the reader. The scientific account explains whether the finding remains interpretable and what uncertainty persists.

Cross-contamination can occur when tools, gloves, work surfaces or containers transfer material between items. Use suitable clean equipment, change gloves as needed, and preserve the relationship between each sample and its source. A laboratory blank cannot reconstruct an undocumented scene transfer.

Commingling distinct specimens destroys information about their separate origins. Once stomach contents and another tissue have been mixed, a later result cannot be assigned confidently to either component. Keep separate specimens separately identified unless an explicitly justified protocol requires a defined composite.

Wrong preservation can lose a volatile target, change chemical species or make an assay unsuitable. Confirm requirements before collection where possible, especially when specimen quantity is limited. If an error occurred, record it and seek laboratory advice rather than adding another chemical to conceal or reverse it.

A product label or presumptive colour reaction must not become a definitive identification in the report. Screening tests can respond to other substances. Document exactly what was observed and reserve compound-specific conclusions for suitable analytical evidence.

Finally, unnecessary delay, missing treatment times and unsupported conclusions about intent can make otherwise good analysis difficult to interpret. A clear chronology and a question that remains open to alternative explanations improve the investigation more than a dramatic account of a supposedly unmistakable scene.

Medical and post-mortem sampling is developed in Post-Mortem Examination and Viscera Collection in Poisoning.

Matrix-specific interpretation is developed in Biological, Non-Biological and Viscera Matrices in Toxicology.

Hair-specific limits are developed in Hair Analysis for Drugs and Chronic Poisoning.