Was Arthur Conan Doyle influenced by any particular forensic techniques or methods used in his time? Were there any specific ones utilized a lot in the Sherlock Holmes series? And if so, what were they?
Doyle makes Holmes notoriously good at analyzing footprints to determine the gender, age, and in some cases, the motivation for the exact path taken by the possible culprit. Footprints have been used in a similar way in real forensive investigations as far back as the nineteenth century.
The second method I can think of that Holmes makes extensive use of is handwriting analysis. This plays a prominent role throughout the entire series, as Holmes is able to tell the age, gender, and dominant hand of the person writing the document. In many cases, he can determine the type of ink used, the native language of the writer, and how similar two pieces of handwritten work are. Victorian society placed a high emphasis on handwriting, which is why several law enforcement agencies use handwriting analysis before the time Doyle wrote Sherlock Holmes. Holmes definitely makes extensive use this technique, although Doyle does overexaggerate it quite a bit.
According to this blog, Sherlock also decodes ciphers:
Sherlock Holmes solves a variety of ciphers...In The Valley of Fear Holmes has a man planted inside Professor Moriarty’s organization. When he receives an encoded message Holmes must first realize that the cipher uses a book. After deducing which book, he is able to retrieve the message...Holmes’s most successful use of cryptology occurs in The Dancing Men. His analysis of the stick figure men left as messages is done by frequency analysis, starting with “e” as the most common letter. Conan Doyle is again following Poe who earlier used the same idea in The Gold Bug (1843).