It's difficult to track how many times an anecdote emerges about real-life law enforcement / crime fighting draws on fictional sources. Below (somewhere) is a story (from Mark Seltzer's book, I believe) about the emergence of FBI profiling and how it drew on classic detective fiction, such as Poe and Doyle. The mind-melding of the Purloined Letter is, of course, FBI profiling avant la lettre, and was later taken up by Michael Mann's Manhunter.

SO - the tag is "fictions of law enforcement," okay? Remember that.

Here's another one, recounted by Christopher Wilson in Cop Knowledge: Lincoln Steffens, author of The Shame of the Cities, a classic muckraking tale of urban corruption in a number of US cities in 1904, tells (in his memoir, and with Jakob Riis as an interloctuor no less!) of being regaled by a Chief Inspector of the true tales of his own heroism, but realizing that this detective was in fact drawing his material from popular detective fictions of the time (which Steffen's knew the detective read and enjoyed -- he surreptiously borrowed them from him from time to time). Writes Steffens "Thus I discovered that instead of detective's posing for and inspiring the writers of detective fiction, it was the authors who inspired the detectives."

(qtd in Wilson, Cop Knowledge, 26)