Forensic Toxicology: Analytical Methods for the Detection of Drugs and Poisons Abstract Forensic toxicology is an important branch of forensic science concerned with detecting, identifying, and, when appropriate, quantifying drugs and toxic substances in biological specimens associated with legal investigations. Analytical findings may help interpret poisoning, sudden death, and driving under the influence of psychoactive substances, and may contribute to evidence considered by legal authorities. Reliable results depend on appropriate specimen selection, proper collection and preservation, a suitable analytical method, and effective quality-control procedures. This article reviews common specimens, major analytical techniques, laboratory workflow, and key challenges affecting interpretation. Keywords: Forensic toxicology, analytical chemistry, drugs, poisons, biological specimens, chromatography, mass spectrometry. 1. Introduction Forensic toxicology combines toxicology, analytical chemistry, and forensic medicine. It aims to detect and identify chemicals that may be relevant to a criminal investigation or a medical event with legal significance, and to determine their concentrations when appropriate. The laboratory’s role extends beyond obtaining an analytical signal: it includes evaluating method suitability, reviewing data quality, and interpreting findings in the context of the case. Substances of interest may include prescription medicines, illicit drugs, alcohol, pesticides, toxic metals, and industrial chemicals. The required examination depends on the medical or legal question. Preliminary screening differs from confirmatory identification and quantitative measurement. 2. Biological Specimens in Forensic Toxicology Blood is important when assessing recent exposure because its concentration may help interpret effects around the time of collection. Urine is commonly used for screening because it may contain the parent compound or its metabolites; however, a urine result alone does not necessarily establish impairment at the time of collection. Oral fluid may be used in some assessments of recent exposure, while hair can provide information about exposure over longer periods, although external contamination and hair-growth characteristics create interpretive limitations. In postmortem investigations, additional specimens such as stomach contents or selected tissues and organs may be collected according to the circumstances and applicable procedures. Interpretation requires knowledge of specimen type, collection time, storage conditions, and the possibility of chemical or biological changes after collection. 3. Analytical Techniques Immunoassays are sometimes used as rapid preliminary screening tools, but cross-reactivity and sensitivity limits can produce false-positive or false-negative results. Important findings may therefore require confirmation using a more selective technique. Gas chromatography–mass spectrometry (GC–MS) is widely used for volatile compounds or substances that can be converted into suitable derivatives. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) is suitable for a broad range of compounds, including substances less suitable for gas chromatography. High-performance liquid chromatography (HPLC) and other spectroscopic techniques may also be used depending on the substance and purpose of the examination. No single technique is ideal for every toxic substance. Method selection depends on chemical properties, specimen type, expected concentration, whether qualitative or quantitative results are needed, and the laboratory’s available resources. 4. Laboratory Workflow The process begins by defining the analytical question and selecting an appropriate specimen. Specimen details and the chain of custody should be documented to ensure traceability from collection to reporting.