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Forensic toxicology is also applied in cases of post-mortem investigations where toxicology is required to establish if an excessive intake of the drug occurred and, if so, whether this contributed to the death. Forensic toxicology testing allows forensic scientists to identify substances and determine a pattern of use. Suicidal, homicidal, and accidental cases of poisoning are common in India and in other countries. With the availability of various agents like pesticides, insecticides, drugs, and chemicals the probability of the misuse of the same is happening. The substances of preference for poisoning are aconite, strychnine, Calotropis, oleander, copper, mercury, arsenic, etc.

The forensic toxicology laboratory, thus, analyses body fluids and tissues to determine the presence of these substances. Toxicologists conduct the analysis, issue reports on their findings, and provide court testimony to interpret the test results.

Forensic toxicology requires expertise in biochemical, pharmaceutical, and phytochemical analysis. Forensic toxicologists collaborate with other professionals such as pathologists, medical examiners, and law enforcement officers to achieve optimal outcomes. In general, forensic toxicology can be divided into two areas:

1. Death Investigation Toxicology (or Post-mortem Toxicology)

Post-mortem toxicology can be defined as the investigation\quantification of drugs (e.g., antiepileptic, neuroleptics), poisons, alcohol or any other chemical aimed to establish their impact on death. The quantification of the chemical concentration in blood or in any other tissue is important in order to establish a cause-effect relationship. For example, analysis of human hair fiber gives information on drugs used and their time distribution (results are normalized on the average hair growth). Similarly, analysis of body parts contaminated with residues of paint, gunshot, drugs or body fluids can be used to link individuals to crimes.

2. Behavioural or Human Performance Toxicology

Behavioural or human performance toxicology is the analysis of the presence, use, or abuse of substances found in illicit trafficking and with no legitimate medical use. Such compounds are classified into classes: Narcotics, Depressants, Stimulants, Hallucinogens, and Anabolic steroids.

Samples for these investigations are obtained from living humans, and avoid interferences due to post-mortem drug redistribution. However, as a result of metabolism different windows for detection must be considered. For example, heroin and cocaine may be detected in urine or saliva if used up to a week before, while marijuana can be detected until a month. These matrices are mainly used in workplace drug testing. The same drugs deposit in hair for months. This type of sample can also be used to detect long-time exposure. However, some drugs persist in the blood for just a few days. Consequently, this is the only matrix that can be used to assess the “state of psychophysical alteration due to drugs of abuse” in criminal proceedings.

Written by: Mr Naqib Harith

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