Forensic toxicology

Keywords: Arsenic hair nails

Specimen:

Supervision of specimen collection and sealing of containers is mandatory to establish a chain of custody. The process must be fully documented.

Living patients: blood (10 mL in fluoride tube), serum, urine (>10 mL), hair, gastric contents as appropriate.

Post mortem: as for living patients plus appropriate tissue especially liver, vitreous humour.

Other materials: as appropriate – consult toxicology/pathologist.

Method:

Drugs and organic chemicals - immunoassay, spectrophotometry, GC, HPLC. GCMS or LCMS is usually required for confirmation.

Metals and some non-metals - atomic absorption spectrophotometry.

Blood gas analysis, eg, Carboxyhaemoglobin.

Reference Interval:

Depends on the drug or poison in question and the circumstances of the case.

Multiple drug ingestions are more common than single drug ingestions and may lower the toxic thresholds of individual drugs.

Alcohol ingestion will be additive in terms of toxicity for most drugs.

Application:

Estimation of drugs or poisons in plasma, urine, gastric contents or tissues of suspected poisoning cases.

Detection of drugs of dependence in the urine of suspected or known drug addicts.

Interpretation:

Consult pathologist or emergency/clinical toxicologist.

Post-mortem drug concentrations may be elevated, compared to ante-mortem concentrations, due to redistribution - consult a forensic pathologist or forensic toxicologist.

In some cases the significance of the results may have to be assessed by a court after expert evidence.

Reference:

Baselt RC.  Disposition of Toxic Drugs and Chemicals in Man. 9th ed. Year Book Medical Publishers, 2011.

Shannon MW, Borron SW, Burns MJ. Haddad and Winchester’s clinical management of poisoning and drug overdose. 4th ed. Philadelphia: Saunders 2007.