A is for Arsenic (22 page)

A post-mortem examination of Percy's body had been ordered, but no obvious signs as to the cause of death could be detected. Dr Thomas Stevenson (1838–1908), an expert in alkaloid poisons, was brought in to examine the remains. He managed to extract a substance from Percy's organs, but there was no chemical test to identify aconitine (and there still isn't). Stevenson had to rely on his extensive knowledge of the taste of alkaloids. The doctor had a collection of 50 to 80 different alkaloids in his laboratory, and he could identify all of them by taste; his party trick was to identify a particular alkaloid by taste before his colleagues could complete the chemical test to confirm its identification. The taste and burning sensations of aconitine were, he claimed, unique. He proposed that as little as 1/60 grain of aconitine, which equates to approximately 1mg, could prove fatal.

Lamson was probably well aware that there was no known chemical test for aconitine, and he had chosen this poison deliberately. Lamson had learned about aconitine when he was a medical student studying under Robert Christison (see page
here
), Professor of Medical Jurisprudence at Edinburgh University and respected toxicologist, who had given evidence in several poisoning cases in Scotland. Lamson's defence did their best to throw doubt on the scientific evidence, as so little was apparently known about aconitine poisoning. The pharmacist who sold the aconitine to Lamson had also come forward to testify. Despite keeping no record of the transaction (he was not required to by law) the sale was so unusual that it stuck in his mind, and when he later read about the poisoning case in a newspaper he contacted the police. Another damning piece of evidence was found in Lamson's notebook, where he had jotted down the symptoms of aconitine poisoning.

To this day no one knows exactly how Lamson administered the poison, though it seems likely it was in either the pill or the cake. A lethal amount of aconitine could have been present in the pill capsule while still leaving plenty of room for it to be filled with sugar. An alternative theory, worthy of Dame Agatha herself, is that the poison was in a raisin in the slice of Dundee cake given to Percy. Despite not knowing precisely how he had carried out the crime, the jury took just 30 minutes to find Lamson guilty, and he was sentenced to death.

Lamson's time in prison forcibly broke his morphine habit; perhaps his newly acquired lucidity made him realise the cruelty of his actions. Four days before he was executed he confessed to the murder of Percy John.

Agatha and aconitine

In
4.50 from Paddington
Agatha Christie uses aconitine to bring an end to Harold Crackenthorpe's life. With Harold out of the way his siblings stand to inherit a greater slice of the Crackenthorpe family estate after their elderly father dies. The method of murder is straightforward. Tablets are sent to Harold Crackenthorpe, ostensibly from his doctor, Dr Quimper. Somebody takes a box normally used for sedative tablets prescribed to Emma (Harold's sister), substitutes aconitine tablets, and sends them from Emma's home, Rutherford Hall, to Harold at his London address. The chemist who made up the prescription could have made a mistake, but he claims no knowledge of the prescription at all. So someone must have got hold of some ordinary tablets and adulterated them with aconitine.

Getting hold of the few milligrams of pure aconitine necessary to kill an adult man would not have been easy, even in 1957. One method would be to extract the poison from an
Aconitum
plant. A relatively pure sample would be needed, to take up as little room in the tablets sent to Harold as possible, and to avoid altering their appearance. Although there is no mention of it in the book it would not be unusual to find monkshood growing in the grounds of Rutherford Hall, or in
nearby countryside. Monkshood is a herbaceous perennial, dying back each winter to regrow the following spring from the roots. The poisoning occurred in the winter, so the murderer would have to know the location of the roots very well, or would have had to plan ahead and collect monkshood roots during the previous summer. Extracting the poison in a crude form would be relatively easy and could be achieved with some technical knowledge and little more than standard kitchen utensils. However, isolating aconitine from all the other alkaloids present in the plant would be more difficult, and would require more specialised chemical equipment. This seems convoluted and unlikely; it would be much easier to buy the already purified aconitine from a pharmacist.

The compound would have been stocked at a local pharmacy where prescriptions were made up to order. However, in 1957 aconitine was rarely prescribed and, as Miss Marple explains, ‘they were the kind of tablets that are usually kept in a poison bottle, diluted one in a hundred for outside application'. The elderly spinster consistently displays a worryingly detailed knowledge of pharmaceuticals and poison.

Anyone wanting to buy aconitine from a pharmacist would have needed a prescription from a doctor or, if the pharmacist was satisfied that the aconitine was for a legitimate use, the poison would be sold and the poison register signed by the purchaser. Obtaining aconitine was a problem addressed by Oscar Wilde in his short story
Lord Arthur Savile's Crime
. Wilde was writing in the 1880s, a few years before the Lamson case, and even then there were restrictions on the sale of this poison. In the short story Arthur Savile, a carefree young man recently engaged to Sybil Merton, has his palm read and is told he will commit a murder. He decides to kill someone before his wedding so that he can begin his married life without the burden of not knowing when or whom he might kill. After careful consideration he elects to kill an elderly aunt using poison. Lord Arthur conducts his research by reading a pharmacopoeia and
Erskine's Toxicology
, and finds ‘a very interesting and complete account of the properties of aconitine,
written in fairly clear English … It was swift – indeed, almost immediate, in its effect – perfectly painless.'
Erskine's Toxicology
does not exist, but Wilde would have done well to read a book on toxicology since, as we have seen, aconitine poisoning, though swift, is far from pain-free.

Lord Arthur calls at a pharmacy in London to purchase the pill he requires. His request is initially refused because a medical certificate is required, but Lord Arthur explains that the aconitine is needed to put down a large dog that has shown signs of rabies. This apparently satisfies the chemist and the prescription is handed over. Mercifully for the aunt, she dies before taking the aconitine, and Lord Arthur has to find another victim.

The poisoner in
4.50 from Paddington
must have convinced the pharmacist that the aconitine was a legitimate prescription. After the murderer obtained the pure aconitine compound they would have added a few milligrams to Harold's tablets. This would be easy if the tablets had been in the form of gelatin capsules (see page
here
), a casing of two halves used to hold powdered forms of drugs that have been around since the 1840s. Because Harold swallowed the tablets straight down with a glass of water, that he would not have initially noticed any unusually bitter taste or burning sensation in the mouth.

The prescription says to take two tablets nightly. Harold had been taking the medication for a while, but thought Dr Quimper had told him that he no longer needed it. Assuming he has misunderstood the doctor Harold dutifully takes two tablets with a glass of water before going to sleep. His death is announced to the family the next morning.

No mention is made of any symptoms displayed by the victim. Perhaps Harold didn't display any. This could only happen if Harold fell asleep quickly after taking the tablets and received a large dose of the poison, killing him rapidly with little time for symptoms to display themselves. Perhaps Christie was saving her readers from a graphic description of the pain and suffering Harold may well have experienced.

The morning after Harold's death it has already been established that aconitine poisoning was responsible, though
we are not told how this was determined. There would be no obvious signs on the body; even a post-mortem examination wouldn't have revealed any damage to organs characteristic of aconitine. Extracting aconitine, or indeed any substance, from body tissue takes time, and it would be easier to extract aconitine from the tablets Harold had been sent, even if it was mixed with other compounds in the tablets. But there is still the problem of identifying the substance that had been extracted. There has never been a colour chemical test available to identify aconitine. A brave or foolhardy pathologist might be able to quickly identify the poison by tasting it and recognising the characteristic burning sensation aconitine produces. Happily, by 1957 more reliable and less uncomfortable methods were being used to identify poisons. Chromatography methods would have been available at this time, although these rely on having a standard available to compare the results. Aconitine is such a rarely used compound, for medicine and murder alike, that it seems unlikely that an aconitine standard would have been readily available. A standard could have been produced, but this would have taken time. Animal tests were another option that was available, but this also would have been time-consuming.

While the victim is alive, blood and urine samples can be used to identify the poison. Even after the poison has disappeared from the blood it may still be traced in the urine because the toxin accumulates in the bladder until it is expelled. Urine is rarely available at post-mortem, so a pathologist would be relying on samples of the liver and kidneys, where the poison is more concentrated. Blood levels of aconitine tend to be very low compared to the levels in these organs. Even so, isolating a tiny amount of poison distributed throughout organs weighing many grams is not an easy task. Though the cause of Harold Crackenthorpe's demise could have been established it would probably have taken longer than suggested in the novel.

Aconitine is an unusual but effective choice of poison for Agatha Christie. There is very little discussion of the properties
of aconitine in the book, and what
is
described is limited to its pharmaceutical preparations – the aspects with which Christie would have been most familiar. However, given the very limited number of murder cases she had to draw on, a few small mistakes – such as the time taken to detect the poison being far too short – are understandable.

Notes

⁵⁷
This pleasing quote is from
Poisons and Poisoners
by C. J. S. Thompson.

⁵⁸
A similar division of the spoils of inheritance crops up in
4.50 from Paddington.

⁵⁹
14
p in new UK money (around 20 US cents); this is the equivalent of around £12.50 ($19) today.

Three Act Tragedy

Mr Babbington was peering across the room with amiable short-sighted eyes. He took a sip of his cocktail and choked a little. He was unused to cocktails, thought Mr Satterthwaite amusedly … Mr Babbington took another determined mouthful …

‘Look,' said Egg's voice. ‘Mr Babbington is ill.'

Agatha Christie,
Three Act Tragedy

AGATHA Christie's 1935 novel
Three Act Tragedy
(entitled
Murder in Three Acts
in the United States) is the only one of her novels to use nicotine as the means of murder. The three victims – a mild-mannered vicar, an eminent doctor and a patient at a sanatorium – appear to have nothing in common. The first death is, after some consideration, initially attributed to natural causes; the second occurs under similar circumstances, with the victim displaying almost identical symptoms before dying – after which it is realised that there's a murderer about.
The third is carried out to silence a witness. All the victims are dispatched by a lethal natural product, nicotine. Among the suspects are an actor, a dressmaker, a playwright and even a butler, none of whom seem to have a motive. Fortunately, Hercule Poirot is on hand to sort through the red herrings and reveal the culprit.

Most people are aware that nicotine is dangerous. It is indirectly responsible for thousands of deaths annually through smoking; nicotine causes the addiction, but it is other compounds from tobacco smoke that usually kill smokers. Pure nicotine, however, is highly toxic in its own right, and has been the cause of many fatalities; it has rarely been used in murder, though. This is surprising given its ready availability, but perhaps because it is so commonplace we struggle to believe that such an everyday substance could be used to kill.

The nicotine story

At room temperature, nicotine is a clear colourless liquid. It mixes completely with both water and alcohol and has a strong, distinctive taste. When exposed to air it turns brown, almost whisky-coloured. The pure liquid gives off a characteristic tobacco-like smell.

The chemical is an alkaloid found in plants of the genus
Nicotiana
. These are part of the family Solanaceae (which we met on page
here
) that includes plants such as deadly nightshade, the tomato and the potato. Nicotine actually occurs in all Solanaceae, but it is
Nicotiana
that has the highest concentrations of the compound. There are many species in the genus, which is native to the Americas, Australia, south-west Africa and the South Pacific, though they are commonly grown in gardens across Europe for ornamental purposes.
Nicotiana tabacum
is the species grown commercially, with tobacco products derived from the dried leaves of the plant.
⁶⁰