Sherlock Holmes and Modern Forensics

Published for NC Criminal Law on November 01, 2018.

My recent criminal justice class involved forensics so, being in London, it seemed only fitting to take a look at Sherlock Holmes and his methods. What was the impact of Arthur Conan Doyle’s fictional character on the development of forensics? What can we learn from Holmes more than 130 years after his first appearance in the classic A Study in Scarlet?

Let me get a couple of things out of the way. First, A Study in Scarlet, published in 1887, remains a splendid read (despite some objectionable characterizations of people from other lands). I recommend tucking into the book for a couple of hours on a rainy day. Given my current surroundings, I was particularly taken by Dr. Watson’s observation about his decision to head to London after his military service in Afghanistan: “I naturally gravitated to London, that great cesspool into which all the loungers and idlers of the Empire are irresistibly drained.” Id. at 13. I agree that London is irresistible. I disagree that it’s a cesspool. I have no comment about loungers and idlers.

Second, I’m skeptical of claims that Holmes, and thus Conan Doyle, invented modern forensics. The 19th century was an era of significant advances in science and medicine. Originally a physician, Conan Doyle built on his medical knowledge and experience and applied “theories and concepts of the time into the use of forensics by his character.” Eric Andrews, How Sherlock Holmes Invented Modern Forensics (May 2015).

That’s not to say Holmes didn’t have an impact on forensics. By the late 19th century, for example, academic papers had identified “the need for a systematic approach to a crime scene,” but the actual practice lagged far behind. E.J. Wagner, The Science of Sherlock Holmes at 80 (2006). Holmes’ renown for meticulously examining crime scenes may well have influenced the adoption of a more methodical approach. See Stanton O. Berg, Sherlock Holmes: Father of Scientific Crime and Detection, 61 Journal of Criminal Law and Criminology 446 (1971).

The Holmes’ stories are also cautionary tales about the limits of forensics. For all the sound techniques that appear in the stories—such as the use of a reagent as a preliminary indicator of the presence of blood, gleefully described by Holmes to Watson in A Study in Scarlet—Holmes employed some dubious techniques—such as the calculation of a person’s height based on the distance between his or her shoe prints, that is, stride length. (A person’s stride length in a given situation obviously may differ depending on a range of circumstances.)

A variation of stride analysis—forensic gait analysis—recently emerged in UK criminal courts. The technique involves visual comparison of two or more video recordings, such as from a closed circuit television camera, a common device here. The aim is to determine whether the person in the recordings is the same person or a different one based on the manner of walking or gait.

As with Holmes’ discredited stride analysis, the technique has been questioned, most notably by the Royal Society, an independent academy of scientists in the UK. Working with the judiciary, the Royal Society issued a primer for courts on forensic gait analysis in 2017. The conclusion? Gait analysis has value in a controlled clinical setting in working with patients with physical impairments; but the scientific support for forensic use is limited and its reliability questionable. See also Lisette Payne, Royal Society Forensic Primers, Forensic Science in North Carolina (Apr. 13, 2018).

The UK has proposed a code of practice imposing strict protocols for forensic gait analysis. These protocols may strengthen the appropriateness of the technique for investigative purposes, but it continues to seem too uncertain to pass muster for trial. Both the UK and North Carolina require the court to assess the reliability of expert testimony before allowing its admission. See UK Criminal Practice Directions Part 19A (Oct. 2018). North Carolina in particular has adopted the stricter Daubert standard of reliability for expert testimony, which can have undue power with juries (as well as with judges when acting as finders of fact).

I can deduce what Holmes would say about the importance of such reliability requirements. They incorporate the elementary principle that scientific testimony must rest on science.

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