The Science of Sherlock Holmes: From Baskerville Hall to the Valley of Fear, the Real Forensics Behind the Great Detective's Greatest Cases

by E. J. Wagner

  Although the concept was brilliant, it was difficult to put to prompt practical use. Many different sorts of insects are attracted to cadavers, and each species has its own breeding habits. Further, as insects are cold-blooded, their reproductive and feeding behaviors are strongly affected by ambient temperature.

  Some insects are particularly difficult to identify, because they imitate the appearance of others. The Syrphidae, or common hover flies, are a prime example. They often appear in the coloring of honeybees or wasps. Although they are largely found in contaminated water, they also target dead flesh. All of these variables made accurate classification of insects of the dead, including their larvae and pupae, very complex.

  For many years after Redi’s experiment, the study of insects in relation to criminal investigation remained largely academic. In 1850, a case in France made innovative use of this natural science. Laborers making repairs in a house of rental flats noticed that a few bricks behind a fireplace were improperly fitted. When the bricks were removed, the tiny corpse of what appeared to be a newborn child was disclosed. The body was mummified, evidently due to the dry heat to which it had been exposed. Insects of various kinds had made their home in the nooks and crannies of the corpse.

  It was not infrequent for workmen to find this sort of piteous remnant in the walls and cellars of ancient houses. Terrified young women had been known to make use of the sturdy, thick construction to hide the sad souvenirs of illicit passion. But was this case a murder, or only the irregular disposal of a child born dead? The police posed a number of questions to the medical investigators. Was the child full term at birth? Had it been stillborn? If born alive, how old was it at death? What was the cause of death? If it was a homicide, who was most likely responsible? The problem was complicated by the fact that four different tenants had lived in the apartment in the previous three years.

  Dr. M. Bergeret of the Hôpital Civil d’Arbois was asked for his opinion, as he had done a number of studies on the changes that occurred in long-buried cadavers. Bergeret approached the problem with the classic techniques of legal medicine. He dissected the body, measured the bones, and minutely examined the desiccated tissues.

  He concluded that the child had been full term and had been born alive. But in order to determine how long the baby’s body had lain in its brick-lined tomb, Bergeret turned to the natural science of entomology, the study of insects. Carefully observing and classifying the moths, mites, and pupae that infested the corpse, he felt certain that the body had been in the wall for at least two years.

  This removed suspicion from the most recent tenants and cast it instead on a young woman who had lived in the flat in the summer of 1848. The neighbors and the landlady, Madame Saillard, believed that the woman had been pregnant, but the child had never been seen. Although the woman was arrested and brought to trial, she was not convicted. Suspicious circumstances notwithstanding, Bergeret was unable to establish that the manner of death was homicide.

  When Bergeret wrote his report of the case in 1855, he stressed both the small amount of knowledge available at the time about the effects of insects on the dead and the need for additional research. Still, he had demonstrated that entomological evidence could be useful to help determine postmortem interval, one of the most difficult problems in legal medicine.

  In 1878, Brouardel was faced with a similar case and found guidance in Bergeret’s work. The mummified newborn corpse that Brouardel autopsied was a nesting place for a number of arthropods. Brouardel asked an army veterinarian, Pierre Megnin, and a professor of the Natural History Museum in Paris to consult.

  They identified butterfly larvae, the skin and feces of mites, and moth larvae. There were millions of mites present, both living and dead. Considering these factors, as well as the remnants of plant life on the body and the number of generations of insects present, the scientists agreed that the cadaver had been placed at the scene between five and seven months before it was discovered.

  The information they gained by observing the flora and fauna of the dead was carefully preserved. They assumed it would be of use in the future. Just as Sherlock Holmes would have demanded, they collected data. As the data accumulated, the connection strengthened between the natural sciences and legal medicine. Megnin continued his research with the intention of writing definitive works on the subject, which he finally accomplished in Fauna of the Tombs, published in 1887 and Fauna of the Cadavers, published in 1894.

  To further understanding of the effects that plant and insect life have on long-buried corpses, large-scale exhumations were carried out during the nineteenth century in France and Germany under the direction of medicolegal doctors. Researchers also exposed the corpses of animals to observe the postmortem changes caused by various insects under a variety of weather conditions. They observed that some beetles carried tiny mites on their bodies, thus allowing the mites access to cadavers. Roaches and other large insects walked through blood and other body fluids and could deposit them some distance from the death scene. Insects were often responsible for postmortem or perimortem injuries. The knowledge prevented a number of judicial disasters.

  In Frankfurt, Germany, in 1889, a nine-month-old baby from an impoverished family died. At autopsy, which was performed three days later, injuries to the face were noted. In spite of the child’s history of illness, the wounds made the police suspect the father of feeding the child sulfuric acid. (At the time, this was a common method of disposing of inconvenient children.) Entomologists, however, demonstrated that the injuries were due to the bites of roaches, and the bereaved father was released from prison after several weeks of incarceration.

  A similar case was reported in Germany in 1899, when a woman was suspected of causing the death of her child because of a pattern of abrasions on the exterior of the child’s body. The frantic mother insisted that she was innocent of any crime and that she had seen the body of her child covered with a blanket of roaches when she had returned from choosing a casket. The physician examining the case put bits of human tissue in glass vessels filled with roaches. The resultant damage caused by the insects proved that the injuries found on the child could be caused in this way, and the wretched mother was spared prosecution.

  These cases and the importance of insects and plants in legal investigation were much discussed in central European scientific circles at the time. Conan Doyle spent months in Berlin and Vienna in 1890. Given his medical background, he was most likely well aware of this growing research.

  Interest in the subject spread rapidly. Research was done in Canada by Wyatt Johnson and Geoffrey Villeneuve and in the United States by Murray Motter. The differences in climate and animal life in various geographical areas made it difficult to usefully share information, but the methods of observation were similar. Bit by bit, the importance of the insect world became evident.

  While scientists in laboratories were struggling to understand the interrelationships of carrion beetles, flesh flies, ants, roaches, and mites, an extraordinary discovery was announced in England. It was 1903, only a year after the publication of The Hound of the Baskervilles, the novel that included the vivid description of the passionate collector of butterflies, Stapleton, and of orchids growing wild on the mysterious moor.

  Walter Rothschild, who was a scion of the famous family of financiers and a dedicated naturalist, and his curator, Karl Jordon, described a fabulous moth that possessed an eleven-inch-long proboscis—long enough to pollinate the mysterious star orchid. The moth had been discovered in Madagascar, just as Darwin had speculated forty years before. Commonly called the hawk moth, it was officially named Xanthophan morgani praedicta in honor of Darwin’s prediction. This was proof that Sherlockian scientific reasoning was a spectacular success.

  In “The Adventure of the Lion’s Mane,” Sherlock Holmes describes his retirement as isolated but implies it is full of scientific curiosity when he says, “My house is lonely. I, my old housekeeper, and my bees have the estate all to ourselv
es.” In the story “His Last Bow,” Conan Doyle tells us further that during his retirement, Holmes has composed his magnum opus: “Practical Handbook of Bee Culture, with Some Observations upon the Segregation of the Queen.”

  If an investigator with Holmes’s interests had truly written this monograph, it would certainly have included some information on the Syrphidae, the hover flies that masquerade as bees and visit the dead. Clearly this would have been more than the casual amusement of a gentleman; it would have been a careful study contributing vital data to forensic science.

  Whatever remains

  • Many humble and tiny creatures continue to contribute to forensic investigation. In 2004, the Journal of Forensic Science reported that human DNA profiles could be obtained from maggots that had fed on a cadaver, even after a postmortem interval of sixteen weeks—raising the possibility that even if a victim’s body had been destroyed, its identity might be established by the maggots left behind.

  • Because maggots devour diseased or decaying flesh, they have proved useful in cleansing wounds in situations where antibiotics are unavailable or their use is inadvisable. The diseased flesh is exposed to flies; the flies deposit eggs in the wound; the injury is bandaged; and the maggots are allowed to remove the damaged tissue. The main difficulty is the provenance of the flies. Their living habits are unsavory, and one can never be sure of where they have been.

  • Leeches, which belong to a phylum of segmented worm, have always played a part in primitive medicine, which found them useful in order to bleed patients. Certain leeches, such as the helpful Hirudo medicinalis, are now enjoying a renaissance as part of the healing arts. They aid in maintaining circulation in surgically reattached parts.

  CHAPTER 4

  Proving Poison

  “How about poison?”

  —Sherlock Holmes in “The Adventure of the Speckled Band”

  Sherlock holmes contemplates poison a good deal. A scientific thinker of his era was bound to do so, as the nineteenth century was a time of seminal discoveries in the detection of venomous substances.

  At Dr. Watson’s first meeting with Sherlock Holmes in the laboratory at St. Bart’s Hospital, Holmes’s hands are covered with bits of sticking plaster, the Victorian precursor to Band-Aids. “I have to be careful, for I dabble with poisons a good deal,” Holmes explains. As a medical man, Watson absorbs this bit of information with equanimity, knowing that experiments in chemistry inevitably involve contact with dangerous materials. Watson does not realize that this mention of poison is a foreshadowing of fascinating problems that he will share with Holmes when the pair investigate cases such as “The Adventure of the Speckled Band,” “The Adventure of the Devil’s Foot,” and A Study in Scarlet.

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  These tales of Conan Doyle are clearly informed by the ambivalent fascination the public felt for poisoners and their crimes. Great throngs of Victorians, full of passionate attention, regularly attended celebrated trials for poisoning as though going to the theater. It excited interest that many of the accused were disarmingly attractive, educated women. As Holmes notes in The Sign of Four, “I assure you that the most winning woman I ever knew was hanged for poisoning three little children for their insurance-money.”

  Women had access to the sickroom and the kitchen. Wellborn, educated women were believed to be implicitly trustworthy. In the nineteenth century, many stood in the dock only because recent advances in toxicology made it possible to detect delicate but sinister handiwork.

  Among the ladies whose trials attracted intense interest and overflow crowds were: Madeleine Smith, the cool and controlled young woman of Glasgow who was accused in 1857 of poisoning her lover by serving him cocoa accented with arsenic (during her trial, the courtroom scene was drawn for a newspaper by the artist Charles Doyle, father of Arthur Conan Doyle; the jury delivered the singularly Scottish verdict of “Not proven”); Florence Bravo, who was suspected of killing her difficult husband, Charles, by placing the heavy metal poison antimony in his burgundy (the jury at the 1876 inquest found that although Charles had been murdered, “there is insufficient evidence to fix the guilt upon any person or persons”); and Adelaide Bartlett, whose beauty and dignified bearing drew sympathy when she was tried at the Old Bailey in 1886 on charges of dispatching her husband with chloroform (the verdict was “Not guilty”).

  In 1889, Florence Maybrick was not so fortunate, as she was convicted on shaky evidence of the arsenic murder of her drugtaking, abusive husband, James. A large part of her conviction rested on the fact that Mr. Justice Fitzjames Stephen, who presided over her trial, was slithering toward senility and allowed copious amounts of extraneous testimony to be admitted. He also delivered a rambling but most unfavorable summation.

  The English public was outraged by what was seen as an unfair verdict. The government compromised by commuting Florence’s death sentence to life imprisonment. She was released in 1904 and promptly wrote a book entitled My Fifteen Lost Years. It sold very well.

  Observing the trial of a woman whose life hung in the balance was titillating, but actually convicting her was avoided. As a rule, convictions were hard to achieve. Reasonable doubt was easily raised, as the times were awash in lethal substances. Mercury was used in the manufacture of hats. Small doses of arsenic and similar substances were often taken as tonics. Women used arsenic to whiten their complexions and belladonna to enlarge the pupils of their eyes. The laws were lax, and poisons of all kinds were readily available for purchase “to rid the home of vermin.”

  At the beginning of A Study in Scarlet, Watson has just returned from Afghanistan and is perhaps unaware of the details of the contemporary cases that fascinated England. But as an educated physician, he undoubtedly knows something of the sinister history of poisoning and the problems that subtle homicides presented to both the judicial system and the medical profession.

  In ancient times, poisoning was both obsessively feared and ferociously punished. The first poisons noted historically were venomous animal substances, usually derived from reptiles or amphibians. Venin de crapaud, or toad venom, was a favorite. These poisons were often tested on prisoners or slaves, and if proved effective, they were used to coat weapons. Animal poisons are a familiar concept to Holmes, and he is quick to suspect their presence in a number of stories, including “The Adventure of the Speckled Band”:

  “The idea of a snake instantly occurred to me, and when I coupled it with my knowledge that the doctor was furnished with a supply of creatures from India, I felt that I was probably on the right track. The idea of using a form of poison, which could not possibly be discovered by any chemical test was just such a one as would occur to a clever and ruthless man who had had an Eastern training. The rapidity with which such a poison would take effect would also, from his point of view, be an advantage. It would be a sharp-eyed coroner, indeed, who could distinguish the two little dark punctures.”

  Holmes’s thought was prescient. Several twentiethcentury poison cases were solved when a medical examiner’s painstaking external exam disclosed the mark of a hypodermic needle. Among these was the unusual death of Elizabeth Barlow of Thornbury Crescent, in Bradford, England.

  On a May evening in 1957, Elizabeth’s husband, Kenneth, a nurse who worked at a nearby hospital, had called a local doctor to see her, saying that she was very weak and had collapsed in the bathtub. The doctor discovered Elizabeth’s dead body lying on its side in an empty tub. She had vomited. The bereaved husband explained that she had complained of feeling ill and had decided to take a bath. He had fallen asleep waiting for her to return to bed. When he awakened, he discovered her still in the tub, her head submerged in water. He had tried to lift her, but found that even given his nursing skills she was too heavy for him. Therefore, he had drained the tub and tried to resuscitate her where she lay, clearly to no avail. The doctor called the police.

  Detective Sergeant Naylor, who responded, was immediately struck by the fact that Kenneth Barlow’s pajamas were abs
olutely dry. There were no signs of splashed water anywhere in the bathroom.

  The attention of forensic pathologist David Price was requested. Dr. Price at once noticed that water still clung to the crook of the dead woman’s arm, which raised additional questions about Kenneth’s claim of vigorous efforts to save her. The body was brought to the Harrowgate mortuary, and the postmortem was performed at once.

  External examination showed no unusual marks on the corpse’s heavily freckled skin. Internal examination revealed an early pregnancy but no clear cause of death. Price, wielding a magnifying glass, went over the body slowly and methodically a second time. After two painstaking hours, he was rewarded by the discovery of two sets of tiny hypodermic marks on the buttocks. But the toxicology screen had been negative. What could have been injected into this young woman?

  The police, questioning Kenneth’s coworkers, had discovered that his nursing job involved injecting insulin. It was known that Elizabeth was not a diabetic, and therefore injecting her with a large dose of insulin would result in fatal hypoglycemic shock. There was no precedent for murder by insulin, no accepted test.

  Price sectioned out the hypodermic marks. He and A. S. Curry, the toxicologist, injected a group of mice with insulin and a second group with a slurry made from the sectioned tissue. Both groups of mice developed identical symptoms and died. The tests were repeated several times with the same results.

  Kenneth Barlow was found guilty of poisoning his wife and sentenced to life in prison. In the interest of fair play, the jury had not been told of another discovery by the police: that his first wife had died of similar symptoms a few years before. It had been accepted as a natural death. If that woman’s body had been examined with Sherlockian care and each bit of skin peered at through a magnifying glass, tiny marks might well have been found— marks like those of a snake’s bite. If a “sharp-eyed coroner” had distinguished “two little dark punctures” in that case, Elizabeth Barlow might not have married the snake named Kenneth.