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Investigations 101: Lessons from Sir Arthur Conan Doyle’s The Adventures of Sherlock Holmes

May 3, 2023  By Gilles Renaud

The Case of A Scandal in Bohemia was published in 1892 and is the first found in the collection titled The Adventures of Sherlock Homes. Sherlock Holmes has been synonymous with excellence, indeed perfection, in detective work ever since. Holmes typified the ideal that a solution to a crime required information and that conclusions were quite premature and highly doubtful until all data had been mined and analyzed, and that science, not intuition, was the foundation for all success in police work.

As set out in Part I of this short story, his confidant and best friend Dr. Watson asked Holmes:

“This is indeed a mystery,” I remarked. “What do you imagine that it means?”

“I have no data yet. It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.”


My objective in analyzing this short story is to provide guidance to detectives working in 2023, drawn from Sir Arthur’s imagination, to illustrate current elements of controversy in detective work and to offer insights into investigative controversies touching upon interviewing witnesses and suspects, the exercise of judgment including understanding human nature, and the signal need for professionalism in this vital aspect of the protection of the community.

Interviewing witnesses: Leading the witness

An excellent illustration of a poor interview marred by leading is seen in Part II: “… I found myself mumbling responses which were whispered in my ear, and vouching for things of which I knew nothing …”

I concede that this complaint of repeating information not known and vouching for things not otherwise within the understanding of the person is not taken from an interview, but it makes plain what the interviewer must avoid: putting suggestions to the witness and eliciting the endorsement of information not otherwise within that person’s knowledge. To do so is to invite a strong objection from the defence and a decision by the judge, taking notes with a computer, to delete all of the testimony, not just the leading questions and answers, as being unreliable.

Demeanour evidence: The importance of knowledge of the persons whose demeanour is being assessed

I begin by noting these lines in Part I of A Scandal in Bohemia:

… I was seized with a keen desire to see Holmes again, and to know how he was employing his extraordinary powers. His rooms were brilliantly lit, and, even as I looked up, I saw his tall, spare figure pass twice in a dark silhouette against the blind. He was pacing the room swiftly, eagerly, with his head sunk upon his chest and his hands clasped behind him. To me, who knew his every mood and habit, his attitude and manner told their own story. He was at work again.

This introductory paragraph makes plain two vital elements of demeanour that the investigator may assess to further the aims of justice: non-verbal language that purports to communicate information, and the signal advantage enjoyed by the person who seeks to judge these silent signs if they are well acquainted with the subject and their habits in this regard.

It seems obvious that Dr. Watson, as an investigator, would not be wrong to conclude that Holmes was pondering a case, a crime. Surely, he was correct to write in his memoirs, “To me, who knew his every mood and habit, his attitude and manner told their own story”. The better question to pose is: would others who did not know Holmes quite as well be on sound ground to conclude as much? And, irrespective of the answers to either question, the only valuable question that an investigator requires an answer to is: what was he thinking and does attitude and manner reveal anything tangible, anything objective, upon which to conclude as to correct facts? Stated otherwise, what story did this tell, and was the story credible and reliable, especially considering that one can assume a favourable demeanour as well as hide a tell-tale one to avoid detection of one’s recent crime?

In other words, if his good friend was not convinced that Holmes was “glad” to see him, should we trust Dr. Watson to read the more challenging aspects of Holmes’ mannerisms and gestures?

I do not wish to suggest that judging the demeanour of the witnesses you interview is a waste of time, or an impossible task, based on the brief case law that follows, only to propose that in many instances, a note of caution is required. Things such as the eyes of the witness are commonplace means of expressing thoughts.

Part II of the short story contains a further example of evidence of demeanour that the investigator notes routinely, in person or when reviewing the type of house surveillance video routinely available in this post-modern world: “I was still balancing the matter in my mind when a hansom cab drove up to Briony Lodge, and a gentleman sprang out. He was a remarkably handsome man, dark, aquiline, and moustached—evidently the man of whom I had heard. He appeared to be in a great hurry, shouted to the cabman to wait, and brushed past the maid who opened the door with the air of a man who was thoroughly at home.”

Having illustrated common examples of demeanour, I now set out a few key passages from the case law to further the investigator’s understanding of this controversial subject, taken from R v Batchelor, [2022] OJ No 560 (Sup. Ct.), a well-reasoned judgment of Roger J.

50 Caution is required in considering favourable or unfavourable demeanour evidence. As indicated in R. v. M.M., 2016 ONSC 5027, at para. 59, and R. v. D.M., 2016 ONSC 7224, at para. 23, whether demeanour is related to in-court or out-of-court behaviour, it can be easily misinterpreted. As noted in R. v. Levert (2001), 159 C.C.C. (3d) 71 (Ont. C.A.), at para. 27, demeanour evidence has been known to play a role in wrongful convictions. Indeed, demeanour evidence alone can be a notoriously unreliable predictor of the accuracy of the evidence given by a witness as “the law does not clothe the trial judge with divine insight into the hearts and minds of the witnesses” and demeanour should not be sufficient where there are significant inconsistencies and conflicting evidence: R. v. Norman (1993), 16 O.R. (3d) 295 (C.A.), at p. 314, citing Faryna v. Chorny, [1952] 2 D.L.R. 354 (B.C. C.A), at p. 357.

51 More valuable means of assessing witnesses are to consider the consistency of what they have said on a material matter (internal and external contradictions) and improbabilities (exaggerations or illogical propositions). However, inconsistencies vary in their nature and importance; some are minor or concern peripheral subjects, others are more important or involve a material issue or something material.

52 Demeanour evidence is however not completely irrelevant; for example, the way that a witness testifies, such as unanswered questions, hesitations, challenging counsel, or run-on and unresponsive answers, may in certain circumstances be prudently considered by judges in their assessment of witnesses in conjunction with their assessment of all the evidence: see e.g., Hull, at paras. 8-9; R. v. Boyce, 2005 CarswellOnt 4970 (C.A.), at para. 3. Regardless, trial judges should not unduly rely on demeanour to make credibility findings, and any reliance on demeanour must be approached cautiously because looks can be deceiving. Importantly, a witness’ demeanour cannot become the exclusive determinant of his or her credibility or of the reliability of his or her evidence: see R. v. Hemsworth, 2016 ONCA 85, 334 C.C.C. (3d) 534, at paras. 44-45. Indeed, it is often difficult to accurately understand why a witness, whom the judge has never met before, exhibits certain behaviours: see R. v. N.S., 2012 SCC 72, [2012] 3 S.C.R. 726, at paras. 99, 101. Demeanour is therefore often of limited value because it can be affected by many factors, including the background of the witness, stereotypical attitudes, and the artificiality of, and pressure associated with, a courtroom or virtual courtroom. A perceived positive demeanour can equally be difficult to assess.

In essence, you must judge the demeanour of those you interview, and you must be mindful of how your demeanour “presents” when you testify.

Human nature: Difficulties estimating how often commonplace things are experienced

Consider this passage from Part 1 about Dr. Watson’s ability to number the times he has “gone up” the stairs at Holmes’ flat”:

“… For example, you have frequently seen the steps which lead up from the hall to this room.”


“How often?”

“Well, some hundreds of times.”

“Then how many are there?”

“How many? I don’t know.”

This is merely a common example of our human condition that includes the inability to be precise about mundane things. Those who profess a clear ability to recall such things are to be doubted, I suggest.

Human nature: Well-understood elements of our behaviour or dangerous stereotype?

Consider this passage from Part II to introduce this subject:

… “Where, then?”

“Her banker or her lawyer. There is that double possibility. But I am inclined to think neither. Women are naturally secretive, and they like to do their own secreting. Why should she hand it over to anyone else? She could trust her own guardianship, but she could not tell what indirect or political influence might be brought to bear upon a business man. Besides, remember that she had resolved to use it within a few days. It must be where she can lay her hands upon it. It must be in her own house.”

The point I make is not that this stereotype of “women are naturally secretive” is quite likely to lead the contemporary cop astray in their investigation, but that it is always necessary to examine our thoughts and beliefs to ensure that we are not acting in accordance with a stereotype.

One method that my training as a judge has provided is to substitute my best friend for the person whose conduct is being scrutinized. Would he or she, reflecting a lot of my own views and experience, by thought to act like this “woman” with those “naturally secretive” inclinations, or would I think my friend an individual? In few words, are we assigning faults or eliminating qualities by reason of the fact the person in question does not look like us, share the same colour, language, background, race, sexual orientation, et ainsi de suite?

Emotions and objective investigations

Sir Arthur Conan Doyle’s Sherlock Holmes was not one to act or to think under the sway of emotion, least of all in terms of “love”. As set out in A Scandal in Bohemia, in Part 1:

It was not that he felt any emotion akin to love for Irene Adler. All emotions, and that one particularly, were abhorrent to his cold, precise but admirably balanced mind. He was, I take it, the most perfect reasoning and observing machine that the world has seen, but as a lover he would have placed himself in a false position. He never spoke of the softer passions, save with a gibe and a sneer. They were admirable things for the observer—excellent for drawing the veil from men’s motives and actions. But for the trained reasoner to admit such intrusions into his own delicate and finely adjusted temperament was to introduce a distracting factor which might throw a doubt upon all his mental results. Grit in a sensitive instrument, or a crack in one of his own high-power lenses, would not be more disturbing than a strong emotion in a nature such as his.

In essence, Doyle set out to create a robot of an investigator, not unlike the half-human, half-Vulcan Spock of Star Trek fame, oblivious to emotion as he sought to answer all the mysteries of space and alien life.

As for me, investigators devoid of emotion are like the crack in the lens described earlier, for it blinds one’s judgment or, at the very least, acts to obscure all the emotions that might have played a role in the drama that led to the crime being investigated. To investigate events often dictated by emotion without being alert to emotional pulls and pushes is akin to attempting to decipher a document written in a foreign language without being able to understand fully that other language.

That is not to suggest that emotions dictate your deductions or decisions, far from it, merely that emotions play a vital part, in some investigations at least. This is far different from becoming emotionally involved with the complainant or putting on blinders when seeking justice.  Objectivity remains the essential element of a sound investigation, but emotions guide the path in many investigations, as do drops of blood in others.


In my other writings, I have observed that modern day police work may be enhanced by resort to literature, and I suggest that this article provides proof to support this proposition. I am hopeful that my review of A Scandal in Bohemia will be of assistance to detectives and that all such unconventional sources of guidance and instruction will be consulted in the officer’s free time. In fact, I encourage those who serve and protect us to request that training time be devoted to reading Agatha Christie’s mysteries, starting with Chapter 13 of Murder in Mesopotamia, in which Hercule Poirot sets out the psychology of detecting crime, or Chapter VII of H.G. Wells’ The Invisible Man as it explains whether an arrest warrant is still valid for a suspect who apparently has no head.

Gilles Renaud will soon retire after serving 28 years as a member of the Ontario Court of Justice. Previously, he was an Assistant Crown Attorney in Ottawa and a prosecutor with the War Crimes and Crimes Against Humanity Section of the Federal Department of Justice. He began his legal career as a defence counsel and has written nine books on the law, including three in French.

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