Poisons and antidotes in forensic examinations
Poisons are harmful chemical or biological compounds that can adversely affect the body's organs or tissues, leading to acute or chronic health issues. In forensic examinations, determining the cause of death may involve searching for signs of poisoning, which can include identifying poisonous residues on the body or through toxicological analyses of bodily tissues. Poisons are categorized into three main groups: biological (like plant-based toxins), chemical (such as industrial substances), and pharmaceuticals (like certain medications that can be toxic at high doses).
While many poisonous substances can be valuable medicines when administered correctly, they can become lethal when misused. Antidotes are substances that can mitigate or reverse the harmful effects of poisons, with some poisons having specific antidotes, while others do not. Antidotes can function by preventing absorption of poisons, competing with the poison for metabolic pathways, or binding to poison molecules to limit their effects. Understanding the complex relationship between poisons and antidotes is crucial in both medical and forensic contexts, highlighting the need for careful handling and knowledge of these substances.
On this Page
Poisons and antidotes in forensic examinations
DEFINITIONS: A poison is any chemical or biological compound that can damage the body’s organs or tissues. An antidote is any substance that can reverse or mitigate the damage done by a poison.
SIGNIFICANCE: A forensic examination to determine cause of death may involve inspection of the body for poisonous residue or for the effects of poison on the body. Body tissues may also be subjected to toxicological analyses to identify any possibly poisonous substances present.
Many substances that are poisonous are, in fact, useful as medicines in the proper doses. The body can tolerate many poisonous substances; much depends on the amount of poison given and whether the body has been able to build up a tolerance to the substance. Some poisons, such as warfarin (a drug that keeps the blood from clotting), were developed as medicines but were later used as poisons. Poisoning can be acute (exposure on one occasion) or chronic (exposure over a period of time).
Types of Poisons
Poisons are generally divided into three large groups: biological poisons (such as plant substances), chemical poisons (such as insecticides and industrial substances), and drugs and pharmaceuticals. Biological poisons fall into three major categories: microbial toxins (produced by bacteria), phytotoxins (produced by plants), and zootoxins (produced by animals). These poisons are generally either ingested (as in the case of poisonous mushrooms) or taken in through the skin (such as through a bite or sting).
Chemical poisons, such as insecticides, herbicides, and industrial or household chemicals, generally cause body damage (skin damage or damage to the parasympathetic system, for example) but may also cause death by depressing the respiratory system. Organic compounds such as hydrocarbons, alcohols, or aldehydes are likely to cause damage involving the route through which they enter the body. For example, if inhaled, these compounds cause lung damage; if ingested, they cause damage to the gastrointestinal tract. Inorganic (generally metal) compounds such as mercury, lead, and cadmium can damage the brain, kidneys, nervous system, and gastrointestinal system. These types of poisons can accumulate in the body over a period of time and cause death.
Drugs and pharmaceuticals, which are generally ingested, tend to cause gastrointestinal irritation and may cause nausea and vomiting. Some compounds, such as morphine, can interfere with muscular activity, eventually causing death. Barbiturates can also depress the central nervous system, leading to respiratory failure and death.
How Antidotes Work
Antidotes work by counteracting the effects of poisons. Some poisons have specific antidotes, whereas other poisons have no known antidotes. One way to counteract a poison is to prevent the gastrointestinal tract from absorbing it. Activated charcoal can bind to a poison, making it difficult for the body to absorb it.
Another possible antidote is the introduction of a substance that keeps the body busy metabolizing it rather than the poison. For example, in ethylene glycol (antifreeze) poisoning, ethyl alcohol is administered. Ethyl alcohol is chemically similar to ethylene glycol, and the body begins to metabolize the ethyl alcohol quickly, leaving the ethylene glycol to pass through the system.
Other antidotes involve binding or trapping poison molecules or the body’s receptors to those molecules. Atropine is used as an antidote to nerve gas; for example, it binds to the nervous system’s acetylcholine receptors, preventing the nerve gas from doing so. Poisons that affect the skin can be counteracted with ointments that trap the poison molecules and keep them from being absorbed by the skin.
Emetics (substances that cause vomiting, such as syrup of ipecac) and cathartics (agents that cause diarrhea) are generally no longer recommended as antidotes for poison.
Bibliography
Aruwa, Christiana Eleojo, et al. "An Appraisal of Antidotes’ Effectiveness: Evidence of the Use of Phyto-Antidotes and Biotechnological Advancements." Molecules, vol. 25, no. 7, 2020, doi.org/10.3390/molecules25071516. Accessed 19 Aug. 2024.
Emsley, John. The Elements of Murder: A History of Poison. New York: Oxford University Press, 2005.
Flanagan, Robert J., and Alison L. Jones. Antidotes. New York: Taylor & Francis, 2001.
Gupta, S. K., ed. Emergency Toxicology: Management of Common Poisons. New Delhi: Narosa, 2002.
Klaassen, Curtis D., ed. Casarett and Doull’s Toxicology: The Basic Science of Poisons. 7th ed. New York: McGraw-Hill, 2007.
Kobylarz, Damian, et al. "Antidotes in Clinical Toxicology—Critical Review." Toxics, vol. 11, no. 9, Sept. 2023, doi.org/10.3390/toxics11090723 Accessed 19 Aug. 2024.
Nelson, Lewis S., Richard D. Shih, and Michael J. Balick. Handbook of Poisonous and Injurious Plants. 2d ed. New York: Springer, 2007.
Stevens, Serita, and Anne Bannon. Howdunit Book of Poisons: A Guide for Writers. Cincinnati: Writer’s Digest Books, 2007.