In the early 1890s, Austrian professor and magistrate Hans Gross wrote the book on investigating criminals -- System der Kriminalistik (or Criminal Investigation). Gross is in fact often credited with creating the very field of criminology, establishing the first institute dedicated to the subject in 1912.
Criminal Investigation, according to The Encyclopedia of Crime & Punishment, "helped to establish the science of forensics, especially in terms of a cross-transfer of evidence; dirt, fingerprints, carpet fibres, or a strand of hair..." The book was considered the bible of criminal investigation throughout the 20th century, and is still used by police forces the world over.
Incidentally, Gross' son Otto was a friend of Franz Kafka (Kafka was also a former student of Professor Gross) and it is said that Kafka made use of Criminal Investigation in writing his classic novel The Trial. Police kudos aside, I don't think there could possibly be any higher recommendation than Kafka cribbing your book for notes. Except basing a character in his novel on you as well, I guess.
That said, it is none too surprising that much of Criminal Investigation might strike the reader all these years later as quaint or otherwise amusing. In any case, Gross. To wit:
"It is often stated, especially in continental treatises on the habits of criminals, that the wrongdoer deposits excrement at the scene of a crime, believing that by doing so he tends to ward off discovery. Whilst this may be, on rare occasions, the explanation of such behaviour it is explicable in many instances by the fact that sheer nervousness and fear render the criminal incontinent so that he leaves traces of this kind at the 'scene' because he cannot help himself."
And here I figured it was for kicks.
Included here are some scans from the 1962 5th edition of the book.
I also have a gallery up at flickr featuring one of the book's highlights, Chapter 8: Slang Expressions Commonly Used By Thieves. So head's up you gymers! Quit sucking the monkey and check it out!