Forensic toxicology

Forensic toxicology is an interdisciplinary field between chemistry, medicine and pharmacy. It provides answers to criminological and legal questions concerning the impact of toxic and pharmaceutically active substances in unnatural deaths, in car accidents (“driving-under-the-influence”) or in drug or medication abuse.

Determining a cause of death, detecting poisoning as well as investigating traffic incidents and questions of criminal liability , all fall under the category of forensic toxicology. Forensic toxicology can involve the detection of the intake of (or abstinence from) addictive drugs in therapy or workplace-testing. It can also validate testimonies or show that someone is meeting probation conditions (criminal law).

Blood, saliva , urine or stomach contents are taken to determine the acute intake of substances; hair or nails are used to indicate long-term intake and body tissues can be analysed post-mortem . Various methods are used. Immunochemically, a specific antigen-antibody reaction may be used to verify even small amounts of antigens. It is theoretically possible to generate antibodies for every antigen; however, many toxins are too small for immunological detection. Another method is chromatography (e. g., high-pressure lipid [HPLC], gas, thin-layer chromatography) where a mixture of substances is assessed by distributing its components dissimilarly between a stationary and a mobile phase. Additionally, the concentration of a dissolved substance can be acquired by measuring the substance`s light absorption using infrared (IR) or ultraviolet (UV) spectroscopy.

If there is a non-specific suspicion of an unidentified poison, the “General Unknown Procedure” is used. This search analysis is able to detect more than 1,000 substances and their waste products. It is conducted with gas chromatography and mass spectrometry.

How did forensic toxicology develop? Even in antiquity , poison was wide-spread. It is said to have been used more often by women, since they were physically weaker than men and would have had a broader knowledge of herbs and plants due to their traditional role of keeping the household. The ancient plant poisons were later replaced with modern poisons such as arsenic , potassium cyanide , polonium , thalium and E 605 ( a pesticide, banned in 2002 (in Germany) due to its high human toxicology and repeated use as a murder weapon). Most recently, the case of Alexei Navalny made its way into the media. He was poisoned with an extremely neurotoxic agent from the Novichok group of chemicals, and only survived with the greatest luck.

Increasingly nowadays, overdosed medication leads to death. For legal purposes, the concentration of the drug needs to be determined, as well as the way it was taken/administered.

What obstacles exist in the field of forensic toxicology? There are numerous standardized procedures to detect poisons in the human body. However, they inherently disregard substances that are not currently known poisons. Such was the case with E605 (pesticide). It was not known to be used as a murder weapon, and was only detected by coincidence. Additionally, many biological substances are degraded or metabolized by the body and are detectable only for a short period of time after intoxification.

Why is an autopsy important? Physicians are legally bound to conduct an autopsy (or as soon as possible) on every cadaver with uncertain cause of death (when weighing over 500g). An autopsy is concerned with the assessment of death as well as identifying the dead person, the time of death, the cause of the death and the type of death. The deceased may be examined by an emergency services doctor. When the identity is known, the relevant general practitioner is asked to do the rest of the examination as they are aware of the medical past of the deceased person. If the physician has any doubts about the natural cause of the death, then a forensic autopsy has to be performed.

What about alcohol? Alcohology is the part of forensic toxicology concerned with detecting alcohols, such as ethanol, as well as corollary alcohols (e. g. methanol, propanol).

The average annual alcohol consumption of 9.6 litres per person, and alcohol often being the cause of death and crime, makes alcohology of great importance. Problems investigated by forensic alcohologists include family settings (and under-age drinking), workplace incidents, traffic accidents and crimes in general. Forensic alcohologists examine culpability and the capability to act, as well as the alcohol concentration in the body.

Since the relevant blood alcohol concentration is the one at the time of the crime and not the one actually measured, forensic alcohologists have to recalculate this concentration on the basis of alcohol kinetics.

Conclusion Forensic toxicology is a key discipline in legal medicine. Not only is it essential for investigating the cause of death, it is also required to determine alcohol- or other drug abuse in accidents. It helps police and other investigators to prove drug misuse in criminal suspects. Forensic toxicology uses a variety of analytical lab methods to detect even smallest amounts of legally relevant substances within the living or dead human body.

EXERCISE: 1. Alcohol is infrequently the cause of death and crime.

a) True b) False

2. If there is no specific suspicion of a certain poison the “General Unknown Procedure” is used.

a) True b) False

3. The “General Unknown Procedure” is able to detect more than 1,000 substances and their waste products. It is conducted with gas chromatography and mass spectrometry.

a) True b) False

You’ll find the answer on the next page.

BIBLIOGRAPHY 1. Lappas NT, Lappas CM: Forensic Toxicology: Principles and Concepts, 1st edition, Elsevier 2016. 2. http://dict.leo.org. 3. www.dict.cc. 4. www.webster-dictionary.org.

CARMEN LOBITZ Carmen Lobitz ist freie Trainerin, Lehrerin und MTA. Sie gründete 1998 in Berlin lobitz seminare, die unter anderem Englischseminare für Health Professionals anbieten. Kontakt: mail@lobitz-seminare.de www.lobitz-seminare.de

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Lösung für Exercise:

1. B 2. A 3. A

Forensic toxicology

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