Introduction:

In most detective fiction, the crimes are solved in very realistic ways, such that forensic methods used in them are also used in real criminal investigations. In, for example, "The Adventure of the Devil's Foot" written by Arthur Conan Doyle, the detective Sherlock Holmes employs the knowledge of medicine in order to identify the effects a suspicious powder found at the murder scene. (Doyle, 16-17). In another story, "The Affair at the Victory Ball", written by the renowned author Agatha Christie, Poirot obtained help from someone's knowledge of the human body to inspect the body of the victim (Christie, p.42). As both authors use similar forensic techniques, those two stories may seem similar. However, just like twins, they may be similar in some aspects but be remarkably different for others.

A similarity comes from the presence of two rules dictated by Knox's decalogue in both stories. Rule IX, which is the presence of a "stupid friend of the detective", is one of them. This allows the author to explain in more detail the event of the crime to the readers. Indeed, when asked about his opinion on the new Lord Cronshaw (Christie, p.44), detective Poirot's friend provides an answer that Poirot found unsatisfactory. As for the detective's friend Watson, he exclaimed that the death of one of the victims was "by suicide" (Doyle, p.17), which was immediately dismissed by Holmes. In both cases, the detective had to reveal the true answer.

Another convention that appears in both stories is rule VIII, which states that the truths behind the mysteries are only revealed at the end. This allows the author to keep some suspense.    Indeed, in "The Adventure of the Devil's Foot", the motives as to why Holmes scraped off ashes from the top of the chimney is unknown (Doyle, p.15). Similarly, in "The Affair at the Victory Ball", the detective Poirot claims that he knows who the culprit is once he was given all the clues but refuses to clarify when asked by Inspector Japp (Christie, p.43). In both cases, the truth was only disclosed at the end.

Despite their similarities, the two stories also possess differences. Indeed, the police are treated differently by the detectives. Holmes, instead of hogging the evidence left behind by the culprit to himself, leaves some for the police to discover (Doyle, p.16) and off ers to answer and to provide them with information (Doyle, p.15). Poirot, however, said that he "always has a desire to keep the threads in his own hands up to the last minute" (Christie, p.44) and refuses to cooperate with the police.