A is for Arsenic (28 page)

It would have been simple to determine morphine poisoning from the post-mortem examination of Mary Gerrard's body.
The easy availability of morphine up until the early twentieth century meant that it was not an uncommon murder method, and scientists had to work hard to develop chemical tests to identify poisons in cases of suspicious deaths.

The real-life Buchanan case brought to light the problems of distinguishing between the different alkaloids that might be present in a body. In 1892, Dr Robert Buchanan was living in New York after divorcing his first wife, and he had taken up with Anna Sutherland, the madam of a brothel. Anna had amassed a huge fortune through her business, and Buchanan decided to marry her. Her fortune was clearly not enough for Buchanan, though, and he insured Anna's life for $50,000. When Anna died of a cerebral haemorrhage Buchanan was quick to collect the insurance money. He hurried back to his native Nova Scotia and remarried his first wife, just three weeks after Anna's death.

Buchanan had almost got away with murder, but friends of Anna were suspicious and thought Buchanan had poisoned her. Two years earlier, Buchanan had taken a particular interest in the case of Carlyle Harris, who had murdered his wife using an overdose of morphine. The authorities had been alerted to Carlyle's use of the poison by the appearance of Mrs Harris's eyes after death. The morphine had caused the pupils to contract to pinpoints; Carlyle Harris was subsequently found guilty of murder. Buchanan called Harris a ‘bungling fool' and a ‘stupid amateur', and pointed out to his friends that if Harris had used atropine eyedrops they would have counteracted the effect of morphine, and no one would have been suspicious. A nurse who attended Anna Sutherland during her final illness noticed Buchanan doing just that – putting drops into Anna's eyes when there was no obvious need to do so.

Anna's body was exhumed, and a post-mortem determined that death was due to a lethal dose of morphine, but the jury needed to be convinced. To demonstrate to the jury the effect of atropine and morphine a cat was brought into the courtroom. Both drugs were administered to the cat to demonstrate the effects on its eyes. This was a straightforward demonstration
when compared to the difficulties in proving that sufficient morphine had been administered to Anna to kill her.

At the time there were a number of chemical reactions that could be carried out on suspect materials, and characteristic changes in colour would identify the presence of certain compounds. Buchanan's defence made a great show of the unreliability of these chemical colour tests. The best-known test for morphine at the time was the Pellagri test; the suspect substance was dissolved in concentrated hydrochloric acid, and a few drops of concentrated sulfuric acid were then added. Next, the resulting mixture was evaporated. A glowing red colour in the residue indicated the presence of morphine. By adding dilute hydrochloric acid, sodium carbonate and tincture of iodine (iodine dissolved in water and alcohol) to the mixture, the glowing red was transformed into green.

The Pellagri test, and many others, had been carefully carried out by Rudolph August Witthaus (1846–1915), a celebrated forensic chemist, in the Buchanan case. However, the defence produced another expert witness, Victor C. Vaughan, professor of chemistry at the University of Michigan. Vaughan claimed that cadaveric alkaloids (alkaloids produced in animal bodies by the decay process) gave the same results as morphine. A series of chemical tests were performed in the court that claimed to show positive colour-test results from extracts obtained from a decayed dog's pancreas. A courtroom was not the ideal place to carry out complex chemical tests, and Vaughan skipped a few of the steps he claimed were not important to the final outcome. Test after test was carried out on test tubes containing morphine, and others containing cadaveric alkaloids. The colours Vaughan produced in his test tubes did not always match up to those stated in the textbooks; either way, the jury became baffled by the array of colours and descriptions of chemical processes. They were left with the impression that, even if the colours produced did not match the textbook descriptions, the same colours were produced by both morphine and cadaveric alkaloids, and the two compounds were essentially indistinguishable. Buchanan was convicted of the murder (and subsequently went to the electric
chair), but this was based on
other evidence
brought against him. The scientific evidence appeared discredited, and newspapers rushed to publish the findings – the reliable Pellagri test was not so reliable after all.

Though the tests performed by Vaughan for the jury did not stand up to the high level of standard procedures expected for such a serious crime as murder, the public's confidence in forensic science was badly shaken. Witthaus had pointed out during the Buchanan trial the importance of performing several tests and comparing the results. Several compounds may give the same result in a few chemical tests, but not all. When preparing for the trial, Witthaus had carried out every known test for the presence of morphine, as well as carrying out physiological studies on frogs. Anna Sutherland had certainly died of morphine poisoning, but a simple and reliable test needed to be found that would convince a jury. After the trial, to reassert the importance and reliability of forensic science, tremendous effort went into establishing reliable, reproducible and unmistakable tests for poisonous compounds. A new level of rigour was brought to the science of forensics, and these processes continue to be tested, improved and replaced by ever more robust methods to this day.

By 1955 there were 30 different methods for testing for morphine. As well as colour tests, pure compounds isolated from cadavers could be identified by their melting points and the shapes of crystals formed when the compounds were converted into salts. Physiological experiments could also be carried out to confirm the effects of a poison in cases where no specific chemical test was available. Even by 1940 (the year
Sad Cypress
was published), the level of scrutiny applied to the analysis and identification of substances in suspected poisoning cases would have been high.

In
Sad Cypress
, Mary Gerrard's murder means the circumstances surrounding Mrs Welman's death also look suspicious, and an
exhumation is ordered. By this time Mrs Welman has been buried for more than a month, but a post-mortem examination is able to confirm that her death was due to morphine poisoning. Although chemical compounds are metabolised in a living body, these processes halt when the body dies; but this does not mean that the drugs and their metabolites are conveniently preserved, frozen in position, waiting for a pathologist to come along and reconstruct the crime by their analysis. A whole new series of chemical reactions can occur during decomposition that may convert any drugs present into new compounds, though many are remarkably resistant to this process. The final metabolite of morphine, the glucuronide conjugates (see page
here
), can be slowly converted back to morphine after death. Unless precautions are taken, chemical reactions, even in sample vessels, can continue to degrade morphine products after their removal from the body. Also, the longer a body has been buried, the more water is lost from the tissues, and this can concentrate the amount of any drug present, so the extent of desiccation must be taken into account.

The most common samples to be analysed for drugs in post-mortem examinations are from the liver, blood and urine. But, depending on the state of decay, not all of these may be available. In Mrs Welman's case liver samples might have been the best option; there would be no urine to analyse, and if she was embalmed (which is likely, as she was rich) her blood would have been significantly altered. Other tissues can be used for drug analysis in post-mortems, but they are much less reliable. For example, muscle tissue may contain the highest drug load from the body, but there are difficulties in extracting these drugs, and they may not be evenly distributed throughout the muscle, which can potentially lead to huge errors. Analysis of hair is also used to determine drug use over time, and though hair is resistant to decomposition it also grows slowly, and drugs take time to find their way to this part of the body. If Mrs Welman had received only a single (massive) dose of morphine just before her death it would not have
showed up in her hair. However, morphine can even be detected in maggots that have fed on human corpses poisoned by the drug.

Even if the quantity of morphine present is accurately determined, it can be difficult to say for sure whether this was the cause of death. Owing to people developing tolerance to opioids, determining levels in the body that might constitute a fatal dose is nearly impossible unless the patient's medical and recreational use of these drugs is well known. Codeine from over-the-counter prescriptions will also potentially show up in tests (as the compound is converted into morphine in the body). Even a strong liking for foods such as poppy-seed cake can skew the results of tests for opioids. Opiates are present in poppy seeds, but the amounts vary greatly. Eating poppy seeds is very unlikely to produce a high unless you eat an awful lot them (about 75g, I am told), but people eating food containing poppy seeds have been known to fail drug tests.

Mrs Welman's drug history would have been well known because her recent illness had required regular visits from the doctor, and two nurses were in constant attendance. Even if she was a dedicated eater of poppy-seed cake, there would only have been very small amounts of morphine present in her body. A pathologist would have been confident in asserting that her death had been due to morphine poisoning.

The evidence against Elinor Carlisle is building; when she stands trial it seems a certainty that she will be found guilty of murder. Poirot's expertise is employed in an attempt to get Elinor off the charges. In his usual methodical way, he sorts through the evidence, talks to those involved, dismisses red herrings and, finally, arrives at the truth.

The doctor attending Mrs Welman privately believes this might be a case of suicide or assisted suicide. The subject had
been broached with the doctor by Mrs Welman herself, but the doctor had declined to give her the requested extra dose of medication. Despite being bedridden, Mrs Welman was an extremely resourceful woman, and the doctor never questioned that she could somehow have managed to obtain morphine, and take a lethal dose, if she had a mind to do so.

The Dangerous Drugs Act of 1920 ensured that opium, morphine and several other drugs could be obtained only with a doctor's prescription, and only from a registered pharmacy. Chemists, dispensers, doctors and nurses may have had access to morphine, but the quantities used were monitored, and stock checks were carried out to ensure that nothing was missing. The difficulty of obtaining morphine is discussed at some length in Agatha Christie's 1955 novel
Hickory Dickory Dock
. One of the characters in the novel is challenged to obtain three lethal poisons, one of which is morphine tartrate. He achieves the feat by posing as a doctor and stealing the drug from the poisons cupboard in a hospital dispensary, but other methods are also proposed. Any present-day poisoner wishing to use some of the methods suggested by Christie will be disappointed to discover that even these underhand methods are unlikely to be successful, as increased checks and controls have since been put in place.