From Socrates, sentenced to drink hemlock in 399 B.C., to Russian mystic Grigori Rasputin reputedly living despite ingesting ten times the fatal amount of cyanide in 1916, and even fictional Sleeping Beauty, poisoning has been a popular way to bring an end to an adversary in real and imagined stories for thousands of years. Until 1840, poisoning was often thought to be a way to “get away with murder”, and it worked because there were no visible signs of foul play. In that year, a French woman named Marie Lafarge became the first person to be convicted of murder by poisoning thanks to new methods for arsenic testing, and the field of forensic toxicology was born.
Toxicology is the study of the adverse effects of chemicals on living organisms. Forensic toxicology takes it a step further, including a number of related disciplines to assist in the detection and interpretation of drugs and poisons in medicolegal death investigations, human performance issues; e.g., driving under the influence, compliance and other related matters. In these investigations, the three main objectives (respectively) are to:
- Establish if toxicants are present and capable of contributing to death
- Establish if toxicants are present and capable of causing behavioural changes
- Establish if substances are present and whether or not they represent legitimate use or exposure, such as prescribed medications or workplace exposures
Forensic toxicology can also be used to determine drugs and dosing for hospital patients, for example in therapeutic drug monitoring and emergency clinical toxicology; identify crimes where toxicants are used to poison or sedate; resolve cases of driving under the influence; and establish whether drugs have been used to improve human performance, as in sport “doping”. For the purposes of this module, we will be primarily discussing post-mortem forensic toxicology.