Blue Line

Investigations 101: What police officers learn by reading The Memoirs of Sherlock Holmes: The Story of “Silver Blazes”

August 18, 2023  By Gilles Renaud

I believe that police officers will learn valuable lessons about the demeanour of those they interview, interviewing and investigative skills, judgment and professionalism, by reading classic detective stories.

In this series on The Memoirs of Sherlock Holmes, by Sir Arthur Conan Doyle, I plan to review each short story to reveal what investigators should do, and what not to do, continuing with the “Silver Blazes”. Briefly put, the crime to be solved surrounds the disappearance of the prize-winning horse, Silver Blazes, the favourite for the English championship, and the tragic murder of its trainer.

The detective story featuring Sherlock Holmes is well known for the quote that follows:

“Is there any point to which you would wish to draw my attention?”


“To the curious incident of the dog in the night-time.”

“The dog did nothing in the night-time.”

“That was the curious incident,” remarked Sherlock Holmes.

As we read the story, we learn that the reason the dog did not bark, though a guard animal, was that the criminal was known to it, and that clue set Holmes onto the successful analytical stream he followed. I propose to review the various elements of investigative work to assist you in your current assignments, and to entertain.

Demeanour evidence and the conduct of successful investigations1

Capture the “bodily” reactions – the facial expressions, the non-verbal communications of those you interview

Too often, police officers consider that demeanour evidence is limited to what witnesses “demonstrate” on the witness stand at trial. That belief is mistaken on several levels, including the fact that witnesses at trial may have had sufficient time and reason to prepare themselves to put on an “innocent face” amongst other elements of demeanour. For present purposes, modern-day investigators should strive to “record” the reaction of witnesses upon being first approached as their initial demeanour might be the most telling, but still quite controversial. The recent case of R. v. Gordon, 2022 ONCA 799, speaks volumes as to the importance of carefully noting (or recording, if possible) the non-verbal responses of persons upon arrest or knowledge that they are being investigated.

At all events, here is what Sherlock Holmes had to say about the reaction of a suspect upon arrest: “… On being arrested he volunteered [innocent information…] When confronted with his cravat, he turned very pale, and was utterly unable to account for its presence in the hand of the murdered man.”

Of course, in detective stories, the author always seeks to have an innocent person demonstrate a guilty demeanour. This illustration is valuable in reminding all to be cautious as an innocent person might well be shocked into pallor by such an event as they might not think anyone will believe in their innocence.

Changes in how a person appears and acts is what you seek to examine and interpret

Note this example:

“… Never have I seen such a change as had been brought about in … that short time. His face was ashy pale, beads of perspiration shone upon his brow, and his hands shook … His bullying, overbearing manner was all gone too, and he cringed along at my companion’s side like a dog with its master.”

Strangers, the persons you interview are

The advantage that writers of detective stories enjoy, and that you do not possess no matter how intelligent and hard working you are, is that they typically employ a narrator who is well-acquainted with the person whose habits and/or demeanour are being assessed. The narrator is thus able to assess fully the scene that is unfolding and specially to “interpret” the non-verbal language being communicated. In this context, we read:

… I was not surprised [by his decision to travel to the ‘scene of the crime’]. Indeed, my only wonder was that he had not already been mixed up in this extraordinary case, which was the one topic of conversation through the length and breadth of England. For a whole day my companion had rambled about the room with his chin upon his chest and his brows knitted, charging and recharging his pipe with the strongest black tobacco, and absolutely deaf to any of my questions or remarks. … silent as he was, I knew perfectly well what it was over which he was brooding.”

Later, this relevant passage appears: “‘Excuse me,’ … ‘I was day-dreaming.’ There was a gleam in his eyes and a suppressed excitement in his manner which convinced me, used as I was to his ways, that his hand was upon a clue, though I could not imagine where he had found it.”

One of your tasks as a detective, in terms of demeanour evidence, is to decipher what the witness is saying, by way of words and by means of their actions, movements, hesitations, facial expressions, etc. In many modern cases, you have a “video” of the “demeanour” of a person, such as the classic denials by President Clinton about sexuality, and you can analyze it at your leisure. In that context, a person caught on camera rambling about with their chin upon their chest and their brows knitted, while smoking, is not necessarily contemplating the crime of the year, as Holmes apparently was, and you must be mindful of the limits of your interpretative abilities. Indeed, you should be wary of the ability of friends of the witness to draw the correct conclusions.

The “Greys Anatomy” list of elements to assess

  • Agitation
  • Expression
  • Eyes
  • Face
  • Flushing
  • Hands
  • Head
  • Laughter
  • Lip
  • Look
  • Manner
  • Pallor
  • Perspiration
  • Shoulders
  • Startled
  • Trembling

Interviewing skills and techniques

Brief, to the point questions, are encouraged

Consider the example found at the outset of this short story: “‘I am afraid, Watson, that I shall have to go,’ said Holmes, as we sat down together to our breakfast one morning. ‘Go! Where to?’” That said, I suggest that you avoid any questions that include a forceful comment such as “Go!”.

All good things come to those who show patience and follow a system. Thus, ask brief and direct questions and exhaust all the information that the witness you interview can provide prior to going back to ask clarifying questions. On the one hand, to ask questions to clarify early on risks the witness taking offence and becoming uncooperative far too early than would otherwise be the case. On the other, the witness may clarify the issue without any intervention by you and this clarity may avoid the judge drawing a negative conclusion from the initial lack of clarity that required to intervene.

“Aide-mémoire” with which to immediately consign notes of what third person states and to recall later

“Silver Blaze” sets out this account of what a young witness reported she heard a suspect state:

‘Oh, indeed! What a stroke of luck!’ he cried. ‘I understand that a stable-boy sleeps there alone every night. Perhaps that is his supper which you are carrying to him. Now I am sure that you would not be too proud to earn the price of a new dress, would you?’ He took a piece of white paper folded up out of his waistcoat pocket. ‘See that the boy has this to-night, and you shall have the prettiest frock that money can buy.’

Most judges, I believe, will assign very little weight to such “reports” unless there is sound evidence of a contemporaneous report that contains details. In addition, I suggest that the further mention, “She was frightened by the earnestness of his manner, and ran past him …” will only serve to reduce the confidence that the Court might otherwise place on this testimony.

Confronting a witness with the facts

I do not suggest that one do so as a matter of course, far from it, but when you have all the independent and objective information you require and you merely wish a witness to confirm what you possess by way of evidence, you may track the technique that Sherlock Holmes employed, as set out below:

“… He tried to bluster out of it, but I described to him so exactly what his actions had been upon that morning that he is convinced that I was watching him. … I described to him how, when according to his custom he was the first down, he perceived a strange horse wandering over the moor. How he went out to it, and his astonishment at recognising, from the white forehead which has given the favourite its name, that chance had put in his power the only horse which could beat the one upon which he had put his money. Then I described how his first impulse had been to [return the horse …] and how the devil had shown him how he could hide the horse until the race was over, and how he had led it back and concealed it … When I told him every detail he gave it up and thought only of saving his own skin.”

Details are the foundation of a successful interview

Consider this example: “‘One moment,’ I asked. ‘Did the stable-boy, when he ran out with the dog, leave the door unlocked behind him?’ ‘Excellent, Watson, excellent!’ murmured my companion. ‘The importance of the point struck me so forcibly that I sent a special wire to Dartmoor yesterday to clear the matter up. The boy locked the door before he left it. The window, I may add, was not large enough for a man to get through.’” This type of detailed information on essential points is likely to be seen as essential and serves to build up the confidence that the Court may assign to that witness and that testimony.

Consider the importance of accumulating details from a witness in advance of later discoveries. In the short story, after the horse has been stolen and the body of the trainer discovered, the police theorized that the victim had defended himself.

As we read: “… It was clear, however, that Straker had defended himself vigorously against his assailants, for in his right hand he held a small knife, which was clotted with blood up to the handle, while in his left he clasped a red and black silk cravat, which was recognized by the maid as having been worn on the preceding evening by the stranger who had visited the stables.”

It is the last part that I wish to emphasize, that dealing with the cravat, said to have been worn by the man who hoped to bribe the grooms. It is obvious that a judge (or jury) will be very impressed if told that the witness had listed the silk cravat as one of the items of clothing when asked by the police to enumerate her observations. Much less weight will be assigned to a subsequent comment to the effect of “Yes, I saw that cravat”.

Investigative skills: what to do, what not to do

Ascertain what the persons who were victimized by the offence were meant to do and whether the plan was complied with

If you are investigating an offence that involved offenders outmanoeuvring a plan of some kind, let us say a kidnapping of a child who is to follow a detailed schedule of travel, it is essential that you ascertain the plan and who was aware of its existence. The short story illustrates this situation as follows: “At a few minutes after nine the maid, Edith Baxter, carried down to the stables his supper, which consisted of a dish of curried mutton. She took no liquid, as there was a water-tap in the stables, and it was the rule that the lad on duty should drink nothing else.” This situation is typical of any suspected “insider” offence.

“Cherchez l’argent”

The typical detective story involves the investigator either looking for money i.e. “cherchez l’argent” or looking for love, i.e. “cherchez la femme” which is a sexist expression no longer to be employed. In this vein, noteworthy as well is the corollary detective angle: “cherchez l’argent” that others do not wish you to earn. Expressed otherwise, who wished that the victim not gain financially.

In the short story, Holmes seeks to identify who might wish to ensure that the owner of the best racehorse in the country, Silver Blaze, not reap a fortune from the forthcoming racing championship. As we read: “[The horse] has always, however, been a prime favourite with the racing public, and has never yet disappointed them, so that even at those odds enormous sums of money have been laid upon him. It is obvious, therefore, that there were many people who had the strongest interest in preventing Silver Blaze from being there at the fall of the flag next Tuesday.”

Circumstantial evidence

Without going into details, I wish to offer my opinion that the courts are wary of circumstantial evidence at the best of times, as information that points in more than one direction or suspect is said to point nowhere, in the final analysis. Nonetheless, alert investigators will seek out circumstantial evidence as it is often of signal importance in directing attention towards one line of inquiry as opposed to another. Consider the example that follows:

… As to the missing horse, there were abundant proofs in the mud which lay at the bottom of the fatal hollow that he had been there at the time of the struggle. But from that morning he has disappeared, and although a large reward has been offered, and all the [residents] of Dartmoor are on the alert, no news has come of him. Finally, an analysis has shown that the remains of his supper left by the stable-lad contain an appreciable quantity of powdered opium, while the people at the house partook of the same dish on the same night without any ill effect.

It is obvious that the investigation will seek to address the question whether the stable-hand was meant to be the only one poisoned, which would be remarkable as it focused attention to his plight, or that the others knew enough not to eat the dish, suggesting an “inside job.”

A second example of how circumstantial evidence may be useful, at the investigative level, is to eliminate a suspect. As we read, “… after the horse had been stolen and the body of the trainer discovered, the police theorized that the victim had defended himself … for in his right hand he held a small knife, which was clotted with blood up to the handle …”

That noted, when a certain person was arrested, “… there was no wound upon his person, while the state of Straker’s knife would show that one at least of his assailants must bear his mark upon him…” Of course, in the pre-CSI era of Sherlock Holmes, the great detective went on to point out that he could not eliminate the possibility that the knife was stained with the victim’s own blood and that he had struck himself in a vain effort to defend himself. That explains why a senior detective stated in the short story: “… I recognize that the evidence is purely circumstantial, and that some new development may upset it.”

Identification evidence – not to be assigned too much weight as it is inherently frail in nature

Consider this passage from “Silver Blaze”:

… Edith Baxter was within thirty yards of the stables, when a man appeared out of the darkness and called to her to stop. As he stepped into the circle of yellow light thrown by the lantern she saw that he was a person of gentlemanly bearing, dressed in a grey suit of tweeds, with a cloth cap. He wore gaiters, and carried a heavy stick with a knob to it. She was most impressed, however, by the extreme pallor of his face and by the nervousness of his manner. His age, she thought, would be rather over thirty than under it.

This is typical of the general description provided by witnesses that include a poor opportunity to observe under what is described as far from excellent lighting, an emphasis on clothing as opposed to physical descriptors of note and general remarks as to age. In fact, it would be far more advantageous if the description of the knob on the heavy stick had been a mole on the face and if the pallor of the face had been a scar.

In addition, I suggest that the further mention “She was frightened by the earnestness of his manner and ran past him …” will only serve to reduce the confidence that the court might otherwise place on this testimony.


“‘See the value of imagination,’ said Holmes. ‘It is the one quality which [Inspector] Gregory lacks. We imagined what might have happened, acted upon the supposition, and find ourselves justified. Let us proceed.’”

The only difficulty is that not all investigators have a story line written that requires them to possess no imagination and Sherlock Holmes far too much! As Henry Fonda, a detective serving in Army Intelligence, famously stated during the movie “Battle of the Bulge”, “Not all cops are flatfoots!”

“Round up the usual suspects”

The passage that follows from “Silver Blaze” tracks the popular expression found in the movie Casablanca: what do you do when there is a serious offence, and you have no real information, and you must appear to be doing something? Well, you round up the usual suspects, which is both counter-indicated and a manifestation of a lack of professionalism.

Inspector Gregory, to whom the case has been committed, is an extremely competent officer. Were he but gifted with imagination he might rise to great heights in his profession. On his arrival he promptly found and arrested the man upon whom suspicion naturally rested. There was little difficulty in finding him, for he inhabited one of those villas which I have mentioned. His name, it appears, was Fitzroy Simpson. He was a man of excellent birth and education, who had squandered a fortune upon the turf, and who lived now by doing a little quiet and genteel book-making in the sporting clubs of London. An examination of his betting-book shows that bets to the amount of five thousand pounds had been registered by him against the favourite.

Share the information you possess and your thoughts with a colleague

Consider this example from the short story:

“‘You have formed a theory, then?’ ‘At least I have got a grip of the essential facts of the case. I shall enumerate them to you, for nothing clears up a case so much as stating it to another person, and I can hardly expect your co-operation if I do not show you the position from which we start.’”

Judgment during your investigations

Amiss, what is

Holmes demonstrates during his post-investigation discussion of the case how he looked for things that were not present, and that should have been, to understand fully what might have occurred. For example, there were sheep that were lame without an explanation, and he surmised that the dead trainer was practising how best to nick the tendon of the horse; as for guard dog, what was amiss was the dog’s failure to bark, explained by the presence of one familiar, and not a stranger seeking to trespass; the fact that only one person was ill by eating a dish that contained a noxious substance could be explained only by finding who had access to the meal at the time of its preparation, etc.


The prudent investigator will always seek out any correct explanation for what seems to be a curious fact. Consider this illustration:

“… A very delicate blade devised for very delicate work. A strange thing for a man to carry with him upon a rough expedition, especially as it would not shut in his pocket.” “The tip was guarded by a disk of cork which we found beside his body,” said the Inspector. “His wife tells us that the knife had lain upon the dressing-table, and that he had picked it up as he left the room. It was a poor weapon, but perhaps the best that he could lay his hands on at the moment.” “Very possible…”

Human nature – Pay the bills of others

Holmes explained to all that he suspected that the victim of the apparent murder had in fact been involved in trying to injure the racehorse and met his fate at the hoofs of the animal. The greatest clue was that the guard dog did not react, understandably, and secondly that the dead man had a bill in his pocket for very expensive gown, a gown that his wife did not own, according to her. He reasoned that no one carries invoices meant for others, and he therefore was leading a double life and needed money, thus his attempted crime …


Consider what Holmes discussed in the middle of the detective story:

… I am afraid that whatever theory we state has very grave objections to it … That is the case as it appears to the police, and improbable as it is, all other explanations are more improbable still…

One should never hesitate to point out to others, including superiors, that there is no good case to be put forward and that all that is possessed by way of theory is improbable at best.

Information in abundance, but little objective facts

On rare occasions, investigators are struggling with this wealth of information but poverty of fact situation. As we read in this short story:

It is one of those cases where the art of the reasoner should be used rather for the sifting of details than for the acquiring of fresh evidence. The tragedy has been so uncommon, so complete and of such personal importance to so many people, that we are suffering from a plethora of surmise, conjecture, and hypothesis. The difficulty is to detach the framework of fact—of absolute undeniable fact—from the embellishments of theorists and reporters. Then, having established ourselves upon this sound basis, it is our duty to see what inferences may be drawn and what are the special points upon which the whole mystery turns…

In effect, Sir Arthur wrote that the prudent investigator should categorize the information received into either the largely useless folder entitled “surmise, conjecture, and hypothesis” or the objective and reliable data into the active folder. As for the ultimate question, how to know “what goes where?”, it is a question of experience, judgment, and the ability to seek out the advice of more experienced colleagues.

Modesty becomes you

As you begin your career, you will seek out the advice of more experienced investigators and you will begin to be consulted by your more junior colleagues. As you do so, be careful not to be boastful or to engage in unbecoming self-applause. In this context, note the correct approach put forward by Sherlock Holmes, as he explained why he did not act sooner: “Because I made a blunder, my dear Watson—which is, I am afraid, a more common occurrence than anyone would think who only knew me through your memoirs…”

Reversing the proposition

It is always sound to judge how strong are the conclusions you wish to draw by reversing the proposition of what you hold to be correct. For example, if you suggest person “A” is a good suspect as they were next to the dead body, possessed a weapon and were full of blood, it will be useful to ascertain if “A” was a surgeon who was walking by, saw a stabbing victim and was then impelled to cut open the wound on the spot with a view to then cauterize?

Thus, consider this lengthy passage:

“… [The suspect] has neither a knife nor any sign of a wound. The evidence against him is certainly very strong. He had a great interest in the disappearance of the favourite. He lies under suspicion of having poisoned the stable-boy, he was undoubtedly out in the storm, he was armed with a heavy stick, and his cravat was found in the dead man’s hand. I really think we have enough to go before a jury.” Holmes shook his head. “A clever counsel would tear it all to rags,” said he. “Why should he take the horse out of the stable? If he wished to injure it why could he not do it there? Has a duplicate key been found in his possession? What chemist sold him the powdered opium? Above all, where could he, a stranger to the district, hide a horse, and such a horse as this? …

In effect, a careful investigator does not destroy a plausible case by resort to imagination, in effect by knocking down each brick you create, but they do not as well merely assume that all possibilities are favourable. It takes judgment and experience – one you develop by constant application and the second, by the weight of years and opportunities, including the careful questioning of those more senior to you.

Professionalism in investigative work

Distractions are to be avoided, if possible

This is an obvious point, but the fact remains that we all have family obligations that may hinder our concentration, not to mention other cases, how the Maple Leafs are doing, etc. In this context, consider this passage:

“I confess,” said he, “that any theories which I had formed from the newspaper reports were entirely erroneous. And yet there were indications there, had they not been overlaid by other details which concealed their true import. I went … with the conviction that … was the true culprit, although, of course, I saw that the evidence against him was by no means complete. It was while I was in the carriage, just as we reached the trainer’s house, that the immense significance of the curried mutton occurred to me. You may remember that I was distrait, and remained sitting after you had all alighted. I was marvelling in my own mind how I could possibly have overlooked so obvious a clue…”


I am hopeful that you have gleaned some precious insights from this article and that you will be inspired by the observation that “the dog did not bark” to also find out why, in your investigative work.


  1. Refer to my book, Demeanour Evidence on Trial: A Legal and Literary Criticism, Sandstone Academic Press, Melbourne, Australia, 2008.

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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