by Margalit Fox
Abduction, or “retroduction,” as Peirce also called it, is much like Huxley’s “retrospective prophecy.” Presented with a set of effects—animal tracks, medical symptoms, crime-scene clues—the investigator uses abduction to pinpoint their most logically probable cause.
“A given object,” Peirce wrote, “presents an extraordinary combination of characters of which we should like to have an explanation. That there is any explanation of them is a pure assumption; and if there be, it is some one hidden fact which explains them; while there are, perhaps, a million other possible ways of explaining them, if they were not all, unfortunately, false. A man is found in the streets of New York stabbed in the back. The chief of police might open a directory and put his finger on any name and guess that that is the name of the murderer. How much would such a guess be worth?” (The Glasgow police, of course, did essentially this in fingering Slater.)
The abductive method permits no such precipitate conclusions. “Abduction makes its start from the facts, without, at the outset, having any particular theory in view, though it is motivated by the feeling that a theory is needed to explain the surprising facts,” Peirce writes. “Induction makes its start from a hypothesis which seems to recommend itself, without at the outset having any particular facts in view, though it feels the need of facts to support the theory. Abduction seeks a theory. Induction seeks for facts.”
Abduction, as a group of British scholars explain in an article on medical diagnosis, takes the following form:
FACT C is observed.
IF A were true, C would be a matter of course.
Therefore there is reason to suspect that A is true.
That process is the mirror image of deduction: In deduction the investigator reasons forward, from cause to effect. When Holmes says, as he does in his debut appearance, “In solving a problem of this sort, the grand thing is to be able to reason backward,” he is singing the praises of abduction. To illustrate the differences among deduction, induction, and abduction, Peirce invoked a trio of syllogisms like these:
Deduction
RULE: All serious knife wounds result in bleeding.
CASE: This was a serious knife wound.
THEREFORE [the deduced result]: There was bleeding.
Induction
CASE: This was a serious knife wound.
RESULT: There was bleeding.
THEREFORE [the induced rule]: All serious knife wounds result in bleeding.
Abduction
RULE: All serious knife wounds result in bleeding.
RESULT: There was bleeding.
THEREFORE [the abducted case]: This was (likely to have been) a serious knife wound.
In assembling their case against Slater, police and prosecutors were working deductively, to the detriment of justice. If their preposterous reasoning were schematized, it would look much like this:
RULE: All murders are committed by undesirables.
CASE: Oscar Slater is an undesirable.
THEREFORE, Oscar Slater committed the Gilchrist murder.
Abduction, like the reconstructive sciences of the Victorian age, generates narrative. Zadig used precisely this method in spinning an etiological thread that would account for the observed facts of a case. So, more than a century later, did Sherlock Holmes:
“We are coming now rather into the region of guesswork,” Holmes’s client Dr. Mortimer protests in The Hound of the Baskervilles.
“Say, rather,” Holmes replies, “into the region where we balance probabilities and choose the most likely. It is the scientific use of the imagination, but we have always some material basis on which to start our speculation.”
In case after case, Holmes uses abduction to solve mysteries, reasoning backward until, he said, “the whole thing is a chain of logical sequences without a break or flaw.” In “The Adventure of the Six Napoleons,” a 1904 story, London is plagued by a string of bewildering crimes: the theft and smashing, one by one, of a set of identical plaster busts of Napoleon. To the dependably dim Inspector Lestrade of Scotland Yard, the obvious explanation is that the thefts are the work of a madman, someone “who had such a hatred of Napoleon the First that he would break any image of him that he could see.”
But to Holmes, Lestrade’s theory accounts for the facts only trivially. If a madman were indeed moved to smash Napoleon’s every image, then, why attack those particular busts, “considering,” Holmes points out, “how many hundreds of statues of the great Emperor must exist in London”? And why, Holmes asks further, did the culprit, having made off with one of the busts, wait to smash it until he reached a particular spot in the street? “Holmes pointed to the street lamp above our heads,” Conan Doyle writes. “ ‘He could see what he was doing here, and he could not there. That was his reason.’ ”
These rational observations, combined with empirical legwork, allow Holmes to construct, as he tells Lestrade with no little ego, a narrative of the crime “by a connected chain of inductive reasoning.” The real object of stealing and smashing the busts, he correctly concludes, was to find a priceless jewel concealed inside one of them.
“Holmes…operates like a semiotician,” the critic Rosemary Jann has written. “He ‘reads’ crimes like literary texts, as if they were systems of signs. The true significance of each sign is determined by its relation to others in a particular network of meaning….He is able eventually to recognize the one relationship capable of accounting for all the clues.”
In contrast, the police of the period—in the Holmes canon and all too often in life—tended to think not in terms of a subtle web of contingencies but of a straight line, drawn in unambiguous black and white. Holmes acknowledges this danger in an 1891 story, “The Boscombe Valley Mystery,” when he declares, “There is nothing more deceptive than an obvious fact.”
“Many men have been hanged on far slighter evidence,” Watson concurs.
“So they have,” Holmes replies. “And many men have been wrongfully hanged.”
* Conan Doyle, per common parlance, tended to use “deduction” as a general rubric denoting any type of logical inference.
Chapter 8
A CASE OF IDENTITY
On February 11, 1909, the U.S. State Department approved the Crown’s extradition warrant. On the fourteenth, Detectives Pyper and Warnock escorted Slater, with his baggage, sealed by U.S. Customs, onto the steamer Columbia. Arriving in Scotland on the twenty-first, the ship sailed up the river Clyde. To avoid the throng, straining for a glimpse of the notorious suspect, that was anticipated at Glasgow, Slater was removed from the ship at Renfrew, some five miles away, to be taken the rest of the way by car. As he disembarked, in handcuffs, a member of the Columbia’s crew kicked him.
At Glasgow police headquarters, Slater’s baggage was unsealed. There, among his neatly folded, carefully packed clothing, was the little hammer—not much more than a tack hammer. To the police, the hammer appeared to have been washed, as did a fawn-colored waterproof coat, which bore dark stains. There was an array of hats, including two cloth caps, though nothing resembling the Donegal cap Mary Barrowman had invoked. Nor did police find the checked trousers, fawn spats, or brown boots that some witnesses had described the “watcher” as wearing as he eyed Miss Gilchrist’s house.
“In the fierce popular indignation which is excited by a sanguinary crime, there is a tendency, in which judges and juries share, to brush aside or treat as irrelevant those doubts the benefit of which is supposed to be one of the privileges of the accused,” Conan Doyle wrote in Strange Studies from Life, his nonfiction survey of three murders in nineteenth-century England. “Far wiser is the contention that it is better that ninety-nine guilty should escape than that one innocent man should suffer.”
The Glasgow police appeared to have no such scruples. The case against Slater was weak, and they kne
w it. The brooch clue—the spark that had ignited the manhunt—had long since fallen away. But they had settled on their man, and they would have him. As a result, the case would need to hinge almost entirely on witness identification. But even where there is no intent to deceive, eyewitness memory is a risky proposition. It is patchy, fungible, and highly susceptible to suggestion. Though the inherent unreliability of eyewitness testimony would not be demonstrated scientifically until the late twentieth century, it was already well known anecdotally in Edwardian Britain.
A decade before the Gilchrist murder, another wrongful conviction had driven the point very publicly home. In 1895, a London woman accused Adolf Beck, a down-at-the-heels Norwegian dandy, of having swindled her out of jewelry by posing as a nobleman. On arresting Beck, the police learned that a man playing just this confidence game had swindled almost two dozen women in recent years. Police convened a lineup, known in Britain as an identity parade. Many of the former victims identified Beck—the only man in the lineup with a mustache and distinguished gray hair—as the swindler.
Beck protested that he was a victim of mistaken identity: he had been in South America, he said, when the earlier crimes occurred. But damned by eyewitness testimony, he was convicted and sentenced to seven years’ penal servitude. Paroled in 1901, he was rearrested, tried, and convicted on a similar charge soon afterward. Only in 1904 did police discover the real culprit: a gray-haired Viennese man named Wilhelm Meyer. Meyer, who was living in England under an alias, superficially resembled Beck. He confessed, Beck was pardoned, and the case endured as a seminal cautionary tale.
“It is notorious,” Conan Doyle would write in 1912, “that nothing is more tricky than evidence of identification.” Cognizant of this fact, police and prosecutors in the case against Oscar Slater made certain that it would not fail.
On February 21, 1909, at Glasgow’s Central Police Station, Slater was displayed before witnesses in an identity parade. Standing alongside the dark-haired, olive-skinned suspect were eleven other men: nine pale pink Scottish plainclothes policemen and two pale pink Scottish railway officials. Not every witness could spot the man who had been the “watcher” outside Miss Gilchrist’s home, but those who made an identification chose Slater immediately.
“To expect a row of Glasgow constables and railwaymen to offer ‘cover’ to the identification of a German Jew, of unmistakable foreign appearance, was very much…like attempting to conceal a bull-dog among ladies’ poodles,” the journalist William Park wrote acidly years later. It also did not hurt that several witnesses had been shown Slater’s photograph before the lineup, common practice at the time.
On the twenty-second, Slater, accompanied by his solicitor, Ewing Speirs, was formally charged with Miss Gilchrist’s murder. He was remanded to Glasgow’s Duke Street Prison to await trial. “Slater impressed everyone with his coolness and courtesy,” Peter Hunt wrote. “He asked Mr. Speirs to thank the police for their kind treatment.” Soon afterward, Speirs told the newspapers: “The more I see of Slater the more convinced I am of his innocence. I do not say this, remember, as the agent of his defence. As man speaking to man as I have done with Slater, I cannot help feeling that some dreadful mistake has been made by someone. He is not at all the type of man who would associate with such a revolting crime.”
Before long, the trial venue was changed to Edinburgh, the capital, and Slater was transferred to Edinburgh’s Calton Jail. At the trial, scheduled to begin that spring, the Crown would be represented by James Hart, the procurator fiscal for Lanarkshire, the county that included Glasgow.*1 Hart, who pursued the Slater prosecution with uncommon zeal, would prove to be one of the great malign forces in the case. The defense team included Speirs and the barrister Alexander Logan McClure, who would handle the courtroom arguments.
On April 6, Slater was indicted; his hammer, his raincoat, and one of his hats were sent for testing to Dr. John Glaister of Glasgow University. Glaister, one of the leading forensic medical experts in Scotland, had led the autopsy of Miss Gilchrist’s body. His testimony at trial—including a catalogue of Miss Gilchrist’s devastating injuries and the assertion that Slater’s little hammer could have caused them all—almost certainly helped bring about Slater’s conviction.
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THE QUESTION THAT VEXED Conan Doyle has persisted for a century: Why, when the police knew within a week that the brooch clue was false, did they pursue Slater anyway? There was a reason, and it resides in an unfortunate accident of history.
At the time of the Gilchrist murder, the identification of criminal suspects was at a crossroads. Standing at that pass, a detective on the trail of a criminal had two choices. There was the way forward, a nascent, rationalist twentieth-century science that would come to be called criminalistics. There was the way back, the murky nineteenth-century pseudoscience known as criminology, rooted in the work of Cesare Lombroso and his ilk. In taking the path of criminology, the Glasgow police doomed Slater. Then again, as was confirmed long afterward, framing him for the Gilchrist murder had been their objective from the very start.
The Victorian age has been called the Age of Identification, and the name is apt. The technology that had spawned the era’s cities also fostered mobility: railways and faster steamships let ordinary people cross borders with ease. The trouble was, they let criminals do likewise. And the cities themselves, in their seething anonymity, offered criminals safe havens in which identity became fluid: one had only to adopt an alias and dissolve into the crowd. As a result, the anxieties of the era focused on the need to identify criminals at a distance. But individual identification—finding the uniquely correct needle in a dense cosmopolitan haystack—is no mean feat, and for the Victorians, an urgent question was how to go about it.
The identification of any criminal suspect involves the reading of signs: at the crime scene, on the victim, or on the criminal himself. Today, the best-known way of doing this is through forensic sciences like ballistics, fingerprinting, serology, and toxicology. These are the reconstructive sciences of the postmodern age, letting investigators reestablish past events after the fact, sometimes long after, as DNA fingerprinting has done since its introduction in the 1980s.
But in the Victorian era, forensic science was in embryo: the very concept of a “crime scene” did not exist until the end of the nineteenth century. And forensic investigation as we now understand it—involving rigorous professional protocols, up-to-date scientific procedures, and state-of-the-art police laboratories—did not begin to come into its own until the 1930s and ’40s.
Yet the need for criminal identification is as old as mankind. Think of Cain, who committed the first recorded homicide and was marked ever after by God. How, then, did people identify criminals before the mid-twentieth century? The answer lies in the locus of the signifiers: if the signs used today are read mainly off the crime scene, those of the past were read directly off the criminal.
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AN INVESTIGATOR IN PURSUIT of a suspect has three chances at identification. He can identify the suspect after the fact, through forensic analysis of the scene. He can identify him during the fact, via eyewitness testimony. Irrational as it sounds, he can also identify the suspect before the fact, in a preemptive strike meant to safeguard the community. Which technique an investigator employs depends partly on circumstance and partly on the technology available. It also depends—tellingly—on the era’s prevailing attitudes toward crime, criminals, and punishment.
In antiquity and long afterward, Western culture viewed crime as sin. In the interest of public safety, criminals, once known, had to be marked: think of Hester Prynne, and of the vivid capital letter chalked onto the coat of the murderous Peter Lorre in M, Fritz Lang’s 1931 thriller. During the Middle Ages, offenders were often given visible stigmata that signified the nature of the offense. “Branding and ear-boring, as a means of marking the de
viant status of the criminal, had been statutory punishments in England from at least the late fourteenth century,” one historian has written, adding:
A labour statute of 1361 declared that fugitives were to be branded on the forehead with “F” for “falsity.” The Vagabonds Act of 1547…ordered that vagrants should be branded with a “V” on their breast. Ear-boring was introduced in 1572, when a statute was passed requiring all vagabonds to be “grievously whipped and burned through the gristle of the right ear with a hot iron.” By an Act of 1604, incorrigible rogues were to be “branded in the left shoulder with a hot burning iron of the breadth of an English shilling with a great Roman ‘R’ upon the iron.”
The marks offered threefold social control. Visible brands alerted members of the honest public. In principle, they also deterred people contemplating a life of crime. And in an era before widespread literacy and comprehensive penal records, they could be “read” by law officers as signs of prior conviction: criminal suspects were routinely strip-searched in pursuit of them.
In medieval England, an enfranchised system of street justice also dealt with undesirables. It was tied to the concept of the outlaw, a word denoting not a criminal per se but a person deemed to be outside the law’s protection. In legal cases of the era, a criminal defendant (or the subject of a civil action) who repeatedly failed to appear in court—and whom the authorities could not locate—could be declared an outlaw. Once a man had been “outlawed,” any citizen encountering him had the right to do with him as he pleased, including commit homicide.*2 “Outlawry was the capital punishment of a rude age,” two twentieth-century historians have written. “To pursue the outlaw and knock him on the head as though he were a wild beast [was] the right and duty of every law-abiding man.”
