An overview of forensic toxicology, including its role in criminal investigations, the types of substances analyzed, methods of sample collection, and the importance of toxicology in determining cause of death.
Introduction to Forensic Toxicology
Key concepts, scope, and practical applications
| Aspect | Description |
|---|---|
| Forensic Toxicology | The scientific discipline that applies toxicology (the study of chemicals and their effects on living organisms) to legal investigations. |
| Primary Goals | • Identify presence of toxic substances • Quantify concentrations • Interpret findings in a legal context (e.g., cause of death, impairment, poisoning). |
| Typical Cases | • Death investigations (autopsy, post‑mortem) • Driving under the influence (DUI) • Workplace exposure incidents • Drug‑related crimes (trafficking, possession) • Environmental or food contamination events |
| Sample | Typical Matrix | Collection Considerations |
|---|---|---|
| Blood | Whole blood (serum, plasma) | Use anticoagulant (e.g., NaF/EDTA) to prevent degradation; keep refrigerated. |
| Urine | Urine | Often used for drug screening; may require creatinine normalization. |
| Hair | Hair strands (≥3 cm) | Provides a retrospective timeline (≈1 cm ≈ 1 month). |
| Vitreous Humor | Eye fluid | Stable post‑mortem, useful for electrolytes, ethanol. |
| Tissues | Liver, kidney, brain, fat | Reflects chronic exposure; requires homogenization. |
| Breath | Exhaled air | Non‑invasive; mainly for volatile substances (e.g., alcohol). |
| Other | Saliva, sweat, nails, gastric contents | Chosen based on case specifics and substance volatility. |
Key principle: Maintain a strict chain‑of‑custody (documented transfer, storage temperature, labeling) to ensure legal admissibility.
| Technique | Strengths | Typical Applications |
|---|---|---|
| Immunoassays (ELISA, FPIA, CEDIA) | Rapid, high‑throughput screening; low cost | Preliminary drug screens in urine, blood. |
| Gas Chromatography‑Mass Spectrometry (GC‑MS) | High specificity, excellent for volatile & semi‑volatile compounds | Confirmation of alcohol, opioids, cannabinoids, solvents. |
| Liquid Chromatography‑Tandem MS (LC‑MS/MS) | Handles non‑volatile, thermally labile molecules; multi‑analyte quantification | Comprehensive drug panels, novel psychoactive substances (NPS). |
| Headspace GC | Ideal for volatile compounds (ethanol, gases) | Post‑mortem alcohol analysis, volatile solvent detection. |
| Fourier‑Transform Infrared Spectroscopy (FT‑IR) & Raman | Minimal sample prep; useful for solids/liquids | Preliminary identification of unknown powders. |