Here are some notes relating to murder weapons and evidence. As we develop this section some subjects will get theor own pages, for example Clocks & Watches.
A rope was used to strangle a victim and it left an imprint on her neck. The knot left an imprint, and was identified as a clove hitch (double hitch). One of the suspects was a sailor, and he would have used that sort of knot on a regular basis. It's a knot that can be made very quickly and, with skill, using only one hand. Suspicion therefore fell on the sailor, but investigating teams who dug a little more deeply found out that another of the suspects was a regular climber and he was, in fact, the murderer.
Lesson: Look beyond the obvious, but do not discount it.
This has been used in various murder mysteries, including Columbo's 'Now You See Him' story, when a perfect murder was foiled when the detective read the motive on a carbon film ribbon.
One of the more interesting uses of a typewriter in a murder investigation appeared in Sir Arthur Conan Doyle's Sherlock Holmes 1891 story 'A Case of Identity'. Holmes identified the murderer by examining the idiosyncrasies of the letters on his typewriter. The wear and tear means that no two typewriters are ever the same. In 1924 the same technique was used to solve a ransom case.
This is not the first example of Conan Doyle as an innovator. In 'The Sign of Four', published in 1890 Holmes uses fingerprints. Scotland Yard did not start to use them until 1901.
Receipts are sometimes used as evidence as they might prove that someone was in a specific location at a specific time. However, the experienced detective takes nothing for granted because someone can pick up receipts out of a dustbin, so they are not particularly reliable evidence.
Tickets generally can be just as tricky. A suspect claims that he can prove that she left an area because she used her oyster card and a record will be kept of her departure. However, she could have jumped off at the next station and bought an untraceable ticket from the machine to return, so it is not a perfect alibi. It may take days to get the CCTV footage to check all of this, so this alibi given on the night of an investigation should not be accepted as any form of proof (yet many do).
In our Sherlock Holmes themed event we try to do justice to the greatest detective.