Agatha Christie's Methods of Murder by Claire Reynolds

Agatha Christie's stories began in many ways, but the many nasty and subtle methods of murder she wrote down in her notebooks and later came back to in her stories suggest that it was often the idea for a murder that inspired the start of a new mystery. The intricate set-up of a situation in which the victim will be exposed to a deadly dose of poison seems to have been one of Christie's favourite methods for setting in motion her stories. This article may contain spoilers!

Christie's Background in Chemistry
The key to understanding Christie's fascination with murder by poison is the time she spent working as a nurse, and later as a pharmacy dispenser, during the First World War. Writing about her first published novel, The Mysterious Affair at Styles, in her autobiography, Christie suggests "since I was surrounded by poisons, perhaps it was natural that death by poisoning should be the method I selected." The story was written in 1916, while Christie was still working with many of the drugs that would later feature in her work, although it was not published until after the War had ended. The story demonstrates Christie's knowledge of chemistry by having the strychnine poison, normally a harmless component of Emily Inglethorp's medication, made deadly by the addition of bromide that causes it to precipitate out of the liquid and accumulate at the bottom of the bottle. When that final dose is taken, it kills the victim.

Christie's time working with medicines also helped her to come up with less common types of poison to use in her mysteries. It was Harold Davis, a pharmacist from the University College Hospital in London, who inspired Christie to use thallium poisoning in The Pale Horse, where she described its symptoms, including the tell-tale hair loss, in such detail that doctors and detectives were later able to use her novel to recognize real cases of poisoning with thallium. At least two people's lives were saved by Christie readers who remembered her descriptions.

Sparkling Cyanide and Other Poisons
More than 80 victims are poisoned across the entirety of Christie's works. The most common poison used is arsenic, probably because it was such an easy chemical for people to acquire at the time. It could be bought as rat poison or in fly paper, just like the strychnine her murderers were also able to buy at their local shops. Elsewhere, Christie turned to medication: good for the victim in moderation, but deadly when overdosed. The monstrous matriarch Mrs Boynton is killed in Appointment with Death by a large dose of digitoxin, the same substance as she was taking in her heart medication, making the foul play difficult to prove.

Whichever drug or poison Christie uses in her murder plots, she is careful to plan its administration and describe its effects in an accurate manner. In A Pocket Full of Rye, for example, the taxine that has been extracted from the yew hedges around Rex Fortescue's home is added to his breakfast marmalade, where he would be unable to detect its bitter taste. Other ingenious methods of murder include dipping a dart in the poison of the boomslang snake (to kill Madame Giselle in Death in the Clouds), adding prussic acid to a nasal spray used for allergies (to kill Ella Zielinsky in The Mirror Crack'd from Side to Side), and giving several people huge overdoses of nicotine in Three Act Tragedy.

Using a Dead Man's Folly to Conceal Murder
Christie also follows in the footsteps of two of the authors she lists as among her inspirations, Charles Dickens and Sir Arthur Conan Doyle, who both included the use of drugs in their stories, although she does not allow her detectives to indulge in cocaine use themselves. Cocaine instead features as a method of murder in one of the short stories included in Poirot's Early Cases. Just as Christie allowed the use of poison to be disguised by having the victim use the same substance as a medication, here she created a character whose history of drug use enabled them to be killed in a way that the less skilled police detectives attributed to simple accident. In The Affair at the Victory Ball, the victim Miss Courtenay is known to take cocaine, so when she is killed it takes Poirot to realise that something more sinister has happened.

In another of the stories in this collection, The Lost Mine, Christie follows more closely in the footsteps of Dickens. She uses the setting of an opium den to create mystery and confusion, just as Dickens did in his last, unfinished story, The Mystery of Edwin Drood, the work that brings him closest to Christie's world of detectives and murder mysteries, as well as following a long-line of Victorian works which document the high quantity of drug abuse in the Victorian Era. Christie here shows an awareness of the effects of opium and heroin detox symptoms that matches her understanding of poisons, allowing her to introduce some significant ambiguity into the story. She uses the haziness of Charles Lester's drug-addled memory to enable him to be framed for the murder of a man he never met, just as Dickens manipulates the memories and perceptions of his own opium-using character, John Jasper. If anyone other than Dickens could have come up with a fitting ending for Edwin Drood, it would have been Christie.

Murder is Easy, if You Know How to Write
Christie shows a distinct preference for carefully plotted murders conducted through the subtle means of drugs and poisons, but she is not above allowing her murderers to carry out their crimes in other ways, including such unlikely methods as drowning their victim in an apple-bobbing tub at Halloween, or strangling them with the string of their own ukelele. It was probably her own dread of making a mistake when handling potentially deadly chemicals in the pharmacy that made Christie start writing about poisoning. Her anxiety once forced her to get out of bed and go back to the hospital in the middle of the night to check that she had not accidentally put the lid she had been using to hold carbolic acid back onto an ointment jar. Still, it is interesting to consider whether there might be something more to her inclination towards this method of literary murder. Perhaps there is something similar in the mind of a poisoner and a mystery writer.