An overview of forensic chemistry, its role in criminal investigations, and its importance in analyzing physical evidence.
Introduction to Forensic Chemistry
Key concepts, techniques, and applications for the forensic scientist
| Aspect | Description |
|---|---|
| Definition | Application of chemical principles and analytical techniques to identify, quantify, and interpret physical evidence from crime scenes, legal investigations, and regulatory matters. |
| Goal | Provide objective, scientifically valid data that can be presented in court to support or refute hypotheses about criminal activity. |
| Scope | • Drug analysis (illicit substances, pharmaceuticals) • Toxicology (poisons, alcohol, drugs of abuse) • Trace evidence (fibers, paints, explosives, gunshot residues) • Environmental forensics (soil, water, pollutants) • Document and ink analysis • Arson investigation (accelerants) |
Evidence Collection
Pre‑examination (Screening)
Sample Preparation
Instrumental Analysis
Data Evaluation
Interpretation & Reporting
Court Presentation
| Technique | Principle | Typical Applications | Strengths | Limitations |
|---|---|---|---|---|
| Gas Chromatography (GC) | Separation of volatile compounds on a capillary column; detection by FID, ECD, or MS. | Drugs, solvents, accelerants, fire debris. | High resolution, fast analysis of volatiles. | Requires volatility; non‑volatile compounds need derivatization. |
| Liquid Chromatography (LC) | Separation of non‑volatile or thermally labile compounds; detection by UV‑Vis, FLD, or MS. | Pharmaceuticals, metabolites, explosives, dyes. | Handles polar, high‑MW analytes; no volatilization needed. | Longer run times; sometimes lower separation efficiency than GC. |
| Mass Spectrometry (MS) | Ionization → mass‑to‑charge measurement; provides molecular weight & structural info. | Identification of unknowns, confirmation of drugs, toxins. | High specificity, can be coupled with GC/LC. | Expensive, requires skilled operation. |
| Fourier‑Transform Infrared Spectroscopy (FT‑IR) | Molecular vibrations absorb IR radiation; produces a characteristic spectrum. | Polymers, paints, fibers, inks, explosives. | Rapid, minimal sample prep, non‑destructive. | Limited for complex mixtures; overlapping bands. |
| Raman Spectroscopy | Inelastic scattering of monochromatic light; provides vibrational information. | Paint chips, glass, drugs, pigments. | Minimal sample prep, works through containers, complementary to FT‑IR. | Fluorescence interference; |