Analysis: recent high profile poisoning cases have highlighted our dark fascination with death by poisoning 

Death by poisoning has always held a disturbing fascination. Shakespeare’s tragic tale of Romeo and Juliet has enthralled audiences for hundreds of years. The case of Kin Jong-nam, the half-brother of North Korea’s leader who died in only 20 minutes from poisoning by a nerve agent, captivated the world. Indeed, poison has been the weapon of choice for a variety of murderers, from well-respected doctors to evil wartime commanders.

This week, it was a nerve agent attack on a Russian ex-spy and his daughter which has focused attention on poisoning. Former double agent Sergei Skripal and his daughter Yulia, 33, have been in hospital in England since they were found unconscious on a bench outside a shopping centre in Salisbury.

From the Today With Sean O'Rourke Show on RTÉ Radio One, Alastair Hay from Leeds University discusses nerve agents

In a case of poisoning, the first step in the investigation is typically identifying the toxin used. Modern forensic chemists have a barrage of equipment and tests that are capable of detecting and quantifying incredibly small amounts of poison in tissue or blood. In some cases, quantities as small as a trillionth of a gram, which is equivalent to a single second out of 32,000 years, can be detected.

However, it has not always been so easy to determine if poisoning has occurred. Back in 1672, an aristocrat, the Marquise de Brinvilliers, was found guilty and ultimately beheaded for the murder of her lover, father, and brothers. An apothecary called Guy Simon analysed a white powder found at the scene. He undertook a complex process of chemical purification and analysis, ultimately finding the key component to be white arsenic, As2O3, but only after feeding it to a cat, dog and pigeon, all of whom died.

An interesting modern case is that of Alexandra Agutter and the poison atropine. A very poisonous alkaloid, atropine is white, odourless and very bitter to the taste. It is found in the plant deadly nightshade, a single berry of which can kill a young child. Atropine works by blocking certain nerve receptors, particularly in the brain and smooth muscle, and as a result interrupts the activity of the messenger molecule acetylcholine. Victims would start to feel hot as their body temperature increases, their vision would become blurred and their mouth dry.

Belladonna or deadly nightshade (Atropa belladonna)

In 1994, Paul Agutter, Alexandra’s husband, tried to murder his wife using atropine, disguising its bitter taste in a gin & tonic. He then tried to send the authorities on a wild goose chase by spiking several bottles of tonic water with atropine and placing them on the shelves of a supermarket in Edinburgh. Thankfully, his wife did not finish her gin & toxic due to the bitter taste and her husband had miscalculated on how much poison to use. Medical intervention was able to save her life, although she did remained seriously ill for some time after.

A more recent high profile poisoning case was that of Slobodan Praljak. In December 2017, the 72 year old former wartime commander of Bosnian Croat forces, who was sentenced to 20 years imprisonment for war crimes against Bosnian Muslins, died in a hospital in The Hague hours after dramatically drinking poison during his appeal hearing. But what was the potion of choice? Was it arsenic, atropine or cyanide and how did it perform its lethal role?

The spokesperson from the public prosecutor’s office in The Hague, Vincent Veenman, very quickly confirmed that preliminary testing had indicated that the cause of death was "drinking a liquid that can kill" and that the identity of the poison would most likely be discovered. On this, Veenman was correct and just a few days later the toxic cocktail was identified as potassium cyanide (KCN).

Cyanide is one of the quickest acting and has been implicated in several famous deaths. The chemical hydrogen cyanide, HCN, is produced in huge quantities by the chemical industry, with enough generated each month to kill every person on the planet. Thankfully, cyanide is instead used in beneficial processes including the manufacture of pharmaceuticals and polymers.

The toxicity of cyanide is due to its ability to bind to and shut down the enzyme cytochrome oxidase8 (also known as complex IV), which is found in the membrane of mitochondria (the powerhouse of cells). The correct functioning of this enzyme is essential for energy production and uses oxygen, delivered by blood from the lungs, in the final step in the oxidation of glucose. When cyanide renders this enzyme inactive, oxygen in the blood can no longer be used and this is why the presence of bright red oxygenated blood is a symptom of cyanide poisoning.

In a case of poisoning, the first step in the investigation is typically identifying the toxin used

Upon poisoning, the body’s source of energy quickly dries up, due to the arrest of glucose oxidation, with the central nervous system and heart immediately affected. The victim will lose consciousness, a deep coma will develop and breathing will cease. Death can occur within minutes or hours depending on the dose received.

A famous and unsolved case involving cyanide poisoning is that of the Tylenol murders. The murders began in Chicago in 1982 when 12 year old Mary Kellerman was given a painkiller by her parents. The child woke from her sleep complaining of a cold and died a few hours later. That same day, a 27 year old postal worker Adam Janus died under similar circumstances. The deaths continued and, with the help of the Rocky Mountain Poison Center, a link was made to victims taking Tylenol and the poison potassium cyanide.

The perpetrator had bought several bottles of the popular painkiller Tylenol and opened and emptied some of the capsules. He or she then replaced the contents with potassium cyanide before placing the bottles back on the shelves of shops for innocent customers to purchase. No one has ever been brought to justice for these murders.

Advances in forensic science has meant that death by poisoning rarely escapes detection, and this is almost a certainty in the case of a suspicious death. The dramatic case involving Praljak is no different and modern forensic examination allowed officials to quickly determine the poison used. How he got access to the poison, however, may prove to be a more difficult question to answer.

The views expressed here are those of the author and do not represent or reflect the views of RTÉ