Fictional Detectives and Real-Life Forensic Science

On April 10, 1935, Lord Hugh Montague Trenchard, the Commissioner of London’s Metropolitan Police, invited policemen and politicians to celebrate the opening of the new Metropolitan Police Laboratory (MPL). The attendees, wrote a Times correspondent, “have been invited not just to see a collection of microscopes and test tubes, but to open the door to potentialities as yet unrealized by police or science.”¹ But just four years later, Trechard’s replacement, Sir Philip Game, moved to shut down the laboratory on the grounds that it had not made a meaningful contribution to the police’s work. The MPL, it seemed, had not lived up to the lofty expectations.

The MPL’s first decade was made more difficult by bad personnel decisions and the choice to house the MPL in the distant suburb of Hendon rather than in central London with most of the police force. But the MPL’s first technicians also had to contend with the image of forensic science molded by the wildly popular genre of detective fiction. Writers of the era created protagonists whose science always led them to the right conclusion—leading to frustration when real-life forensic science failed to provide such clear-cut answers.

A Laboratory for London

Scotland Yard opened its Fingerprint Bureau in 1901 but had been relying on a network of outside experts for consultations in pathology and ballistics since the early 1890s. Those outside experts had helped the state secure convictions in several high-profile cases, including the 1910 Crippen murder and the shooting of police constable George Gutteridge in 1928. The Daily Telegraph reported the execution of Gutteridge’s killers under the headline “Hanged by a Microscope,” declaring that the scientists who matched the fatal bullets to the killers’ weapons had “sealed their doom.”²

In the early 1930s, Trenchard launched an ambitious plan to create a Police College, an organization that would train an elite corps of officers who could assist his efforts to modernize Scotland Yard. He decided that one of the components of his new College should be a forensic science laboratory, which Trenchard saw as the very epitome of the modern, educated approach to investigation that he hoped to bring to the Metropolitan Police.

After offering the MPL’s directorship to the famed Edinburgh pathologist Sidney Smith, who turned it down, Trenchard offered the job to Spilsbury’s junior colleague James Davidson—which turned out to be a mistake, as the haughty Davidson proved unpopular with both policeman and barristers. Chemists L. C. Nickolls and C.G. Daubney and physicist H. J. Walls soon joined him. The list of chemicals and equipment purchased for the MPL in 1935, along with charts of samples and cases cleared in the 1930s, indicate that the MPL was able to perform a wide range of analyses, including ballistic examinations, tests for blood, semen, poisons and illegal drugs, and examination of documents for signs of tampering.³

Expectations from Detective Fiction

The breathless “hanged by a microscope” headline speaks to the public expectations of forensic science. Those expectations were shaped in part by the adventures of fictional scientific investigators. Detective fiction was Britain’s most popular genre in interwar Britain; in 1939, a full quarter of the books available through W. H. Smith’s lending library were crime novels.⁴

Sir Arthur Conan Doyle’s Sherlock Holmes, whose nineteenth-century adventures surged in popularity during the interwar crime fiction boom, was arguably the most famous detective with scientific interests. Holmes’s mastery of science, especially chemistry, was frequently mentioned as one of the detective’s defining characteristics. In A Study in Scarlet (1887), Holmes was introduced to the reader having just developed “an infallible test for blood stains” that detected the presence of haemoglobin.⁵ But Holmes’s tests for poison and bloodstains were mentioned only in passing, and did not help the detective solve the complex mysteries that formed the central plots of Doyle’s stories.

Instead, Holmes relied on his powers of observation and his wide-ranging knowledge to reach conclusions that would have evaded a lesser intellect. For example, upon meeting Watson, Holmes was famously able to deduce that Watson was an army doctor recently returned from Afghanistan based on his skin pallor, his wounded arm, and his clothing. Doyle portrayed Holmes’s methods not as an investigative technique anyone could learn, but as the product of the detective’s unique genius.

The title of literature’s “first scientific detective” is generally bestowed not on Holmes but on Dr. John Evelyn Thorndyke, a forensic pathologist created by the physician Richard Austin Freeman. Every Thorndyke novel was packed full of scientific details and analyses. In The Eye of Osiris (1911), the pathologist used X-rays to reveal a modern corpse hidden in an Egyptian sarcophagus, and identified the body from the deceased man’s dental records. In A Silent Witness (1915), Thorndyke’s knowledge of Mendelian inheritance proved the key to the mystery.

Although the reader was clearly meant to admire Thorndyke, the true hero of Freeman’s tales was science itself. “Astonishing! and most ingenious. The resources of science at the present day are truly wonderful,” one Freeman villain declared after being caught.⁶ According to Freeman’s depiction, science was never wrong; Thorndyke merely had to let his scientific techniques guide him to the truth.

The cultural image of the infallible scientific detective might seem to be an asset for the new MPL. But the adventures of a Holmes or a Thorndyke bore little resemblance to the reality of the MPL’s work. In real cases most MPL scientists could only speak of what had “probably” occurred, or how likely it was that two samples matched each other. In his 1972 memoir Expert Witness, Walls recalled that court testimony was often difficult for MPL experts during the laboratory’s first years of existence. Any MPL employee who tried to speak in probabilities would be quickly rebuked “with the pained rejoinder ‘Dr. So-and-So, you are here to give us facts, not probabilities.’” Barristers, Walls complained, appeared to believe that “all scientific measurements are made with absolute precision, whereas all scientists know that this is impossible.”⁷

The Power of Fiction

That gap between expectation and reality led to Game’s efforts to close down the MPL in 1939. Only an intervention from Sir Arthur Dixon, a forensic sciences enthusiast in the British Home Office, prevented the laboratory from closure. A series of reorganizations in the post-World War II period made the MPL’s work more central to the everyday operations of the Metropolitan Police, and today the department operates three forensic laboratories.

Problems caused by a gap between pop culture images of forensic science and the realities of forensic investigations, however, are still with us. In October 2000 CSI: Crime Scene Investigation, a drama about forensic investigators, premiered on CBS. CSI aired for 15 seasons and inspired multiple spinoffs and imitators. Its Freeman-like portrayal of science as the infallible key to every mystery also left its mark on the criminal justice landscape. Lawyers in the US have complained about a “CSI effect” leading juries to expect an unrealistic amount of forensic evidence. Actual evidence for the prevalence of the CSI effect has been mixed, but lawyers’ frustrations reflect CSI’s wide cultural reach.

Of greater concern is a 2009 National Academy of Sciences report that cast serious doubt on many common forensic analyses. According to the report, the conclusions from techniques such as bitemark analysis and shoeprint analysis—techniques frequently showcased on shows like CSI—are often not replicable or reliable. A 2015 FBI analysis found an alarming number of errors in the use of microscopic hair analysis. Even so, many of the techniques the NAS and FBI criticized continue to be used to secure convictions. A gap still exists between the pop culture image of forensic science and the realities of what it can do—but many juries remain unaware of just how far CSI is from real life.

Melinda Baldwin

Melinda Baldwin holds a PhD in the history of science from Princeton University. She is a senior editor at Physics Today.

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