I have found a reagent which is precipitated by haemoglobin and by nothing else."Thus was the great detective Sherlock Holmes thrust upon us in December, 1887: as a truth-seeking scientist in a chemistry lab of a London hospital, excitedly waving a test tube in his acid-stained fingers. It would be 13 years before a real test for "the differential diagnosis of human blood" was used by a German medical researcher. Six months later, that test led to the conviction of a murderer.
Holmes' creator, British writer Sir Arthur Conan Doyle, was a physician who realised the vital importance for solving crimes of a test that distinguished between the blood of humans and that of other animals.
Doyle's letters, interviews and memoirs reveal how he made Holmes the epitome of a quirky thinking machine: a detective who conducted investigation based on the scientific approach of observation, deduction, experimentation and conclusion. Along the way, in 56 short stories and four novellas, Doyle fashioned his hero into a forerunner of today's forensic scientists.
A leading light
"Doyle pointed the way to the future," says former University of London chemist John Emsley, who is writing a book called Molecules and Murder, to be published in late 2008 by Britain's Royal Society of Chemistry. In 2002, the Society named Holmes – not Conan Doyle – as an honorary fellow for the pioneering use of forensics. Emsley notes that Doyle drew attention to advances in forensic science emerging in the late Victorian era.
But these techniques were not in general use, other than for autopsies, and their advocates faced an uphill struggle convincing police of their potential. London's Scotland Yard only established its Fingerprint Branch in 1901, two decades after the British journal Nature published evidence that fingerprints provided unique identification.
While the authorities dithered, along came wildly popular stories with Holmes repeatedly solving cases that had supposedly baffled the police by making use of chemical analysis, microscopic inspection, plaster casts of footprints, mathematical calculation, ballistics, fingerprints, code-breaking, handwriting analysis, gunpowder residues, typography and photographic enlargements.
Like all scientists, Holmes published his results and claimed to have produced monographs on topics ranging from the ashes of 140 different tobaccos to tattoo marks and ciphers. Although such references to forensic techniques tailed off in the later Holmes stories, they continued until the final adventure in 1927.
This popularisation of the scientific approach to solving crime was vital to the emergence of modern forensics, says Ray Murray, a forensic geologist based in Missoula, Montana, and author of Evidence from the Earth. "The scientific method... had been around for some time at that point. But Doyle advertised it, he promoted it, he made it a reality."
Murray points to evidence that Edmund Locard, a French pioneer of forensic criminology, read Holmes stories; encountering many instances of what modern criminologists call the exchange principle. This could be the hairs left on your jacket by a cat. Or it could be the zinc and copper filings from a trouser cuff by which Holmes identified a man who was part of a coin counterfeiting operation. "It's the basis of all trace evidence which you see mentioned in television shows like CSI," says Murray.
Locard gave the exchange principle a solid scientific basis, establishing in Lyon, France, in 1910 one of the earliest laboratories devoted to criminal investigation.
The real inspiration
Less speculative is the pioneering role of Sherlock Holmes in the technique of linking a particular typewriter with a text. In "A Case of Identity", published in September 1891, the detective remarks to Watson: "It is a curious thing… that a typewriter has really as much individuality as a man's handwriting."
This story appeared three years before any document examiner wrote about typewriter identification, according to David Crown, who headed the CIA's Questioned Document Laboratory in Washington DC for 15 years.
Who then was the inspiration for this forensic Sherlock Holmes? Early biographies of Doyle give that credit to Joseph Bell, a physician and professor of medicine at Edinburgh University in Scotland, who employed the young author as his out-patient clerk at the Royal Infirmary.
This seems simplistic, however. Certainly, Bell was renowned for diagnosing the afflictions of many patients at the infirmary by mere observation. As a sort of parlour trick, he often also deduced that person's occupation and place of residence. Yet Bell was a medical detective, as were two other Edinburgh faculty members whose quirks. Doyle incorporated into the character of the fictional detective. Holmes was a forensic detective and ranged far beyond medical evidence in his investigations.
The true inspiration for Sherlock Holmes can be detected in this passage from "The Blanched Soldier", in which the detective describes his scientific method: "The process… starts upon the supposition that when you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth. It may be that several explanations remain, in which case one tries test after test until one or other of them has a convincing amount of support."
These words might equally well have come from a forensic scientist today. More to the point, they are almost certainly the views of Arthur Conan Doyle, the real model for the forensic Sherlock Holmes.
