This is a backwards answer, but Doyle partially based Sherlock Holmes on a real-life pioneer of forensic science, a man named Dr. Joseph Bell.

Bell was a medical doctor from a long line of medical doctors (his great grandfather identified syphilis and gonorrhea as two different diseases), and a bit of a polymath - as well as being a member (and eventual president) of the Royal Medical Society of Edinburgh, he published at least one article on architecture, monographs on chemistry and women's rights (he was an advocate of allowing women to study medicine - Florence Nightingale was a fan) and a surgical manual.

Doyle was one of his students, and was very impressed with Bell's diagnostic method, which involved close observation of everything possible about a patient - accent, dress, the way they walked, marks on the fingers.... Bell's "coldness of manner" also made an impression on Doyle and can be seen in Holmes' character as well. The physical description of the two is similar, too.

From Doyle's autobiography:

I thought of my old teacher, of his eagle face, of his curious ways, of his eerie tricks of spotting details. If he were a detective, he would surely reduce this fascinating but unorganized business to something nearer to an exact science....

It was surely possible in real life so why should I not make it plausible in fiction? It is all very well to say that a man is clever, but the reader wants to see examples of it - such examples as Bell gave us every day in the wards. The idea amused me.

At the heart of Bell's similarity to Holmes is the same "Method" that made him so important in the field of forensics. Summarized in the Fall 2009 issue of The Forensic Examiner:

The successful diagnosis, he told students, rested on three things: “Observe carefully, deduce shrewdly, and confirm with evidence.” For him, the Method—the “accurate and rapid appreciation of small points in which the diseased differs from the healthy state”—was one of the most important things he could impart to young medical minds. Among the reasons was that impressing patients with such intimate knowledge inspired their cooperation in the healing process. It was paramount, then, to make a study of people.

“Nearly every handicraft writes its sign-manual on the hands,” Bell once wrote. “The scars of the miner differ from those of the quarryman. The carpenter’s callosities are not those of the mason. The soldier and sailor are different in gait.” Ornaments, tattoos, and clothing added more dimension, as did posture and demeanor. But “mere acuteness of the senses” was not enough. One also had to study in minute detail subjects that would aid in making distinctions: the diverse odors of poison, for example, or of different perfumes.

...

In one case, an elderly woman dressed in black entered, and Bell asked, “Where is your cutty pipe?” Startled, she produced it from her purse. Bell then told his students that from a small ulcer on her lower lip and a glossy scar on her cheek, he knew she used a short-stemmed pipe that lay close to her cheek when smoking.

...

Among Bell’s training tricks was to pass around an amber-colored fluid, which he described to students as a potent drug that tasted quite bitter. Still, because they must learn how different substances tasted and smelled, they’d have to follow his example. He would dip his own finger, taste it, and make a face, and then pass it to a student. The concoction did taste quite bad, but each aspiring physician obediently tasted. Bell would then tell them that they’d missed the most important part of the experiment: he’d used one finger to dip into the liquid, but placed a different finger into his mouth. He hadn’t tasted the bitter brew at all. Thus, they’d seen but not “truly observed” him.

Beyond using his Method to impress medical students, Bell helped authorities investigate several high-profile crimes, and may have identified the perpetrator of the Jack the Ripper murders. He refused to give details (though some of the stories are described in that Forensic Examiner article).

The University of Edinburgh's Centre for Forensic Statistics and Legal Reasoning was originally founded as the Joseph Bell Centre for Forensic Statistics and Legal Reasoning after the famous pathologist.

To piggyback off this question, how (if at all) did the Sherlock Holmes canon influence the way people outside of the law-enforcement profession think about police investigations? Was there an equivalent to the CSI Effect?

what happened ?

From "Bloody Buisness: An Anecdotal History of Scotland Yard", by H. Paul Jeffers:

p95-103 describes the relationship between Doyle, Sherlock Homes, the public, and the London Police in great detail.

The first bit describes the city of London's situation when Doyle first went there as a child, and shows possible inspirations for portions of the later Sherlock Holmes works in murders and scenes Doyle was exposed to. The book quotes a biography of Doyle written in 1976, saying that the failure of the police to solve the Ripper murders left people unsatisfied, which left a perfect environment for stories of a fictional detective.

p97 begins to go into the police attitude towards the books, which can generally be summed up as hostile; Doyle presented the Yarders as blatantly incompetent - while the Yarders felt the character got to avoid the worst end of policing, such as breaking up bar room brawls, public contempt, and getting paid the same as folks who dug ditches.

Doyle was also an advocate for justice, and in at least two cases was deeply involved in acquitting people from crimes they were accused of - in one case, the description of the case Doyle became involved in looks very much like police railroading getting derailed by Doyle being persistant and logical. This did not contribute to a warm feeling from the police towards the writer or his detective.

That said, in 1974 the commissioner of the Metropolitan Police was a guest speaker at the Sherlock Holmes society annual meeting, and said that while the police tend to regard the Holmes stories with derision, you could ascribe to the stories the first instance of the public seeing the investigation of crime as a respectable job, a good versus evil with the investigation on the side of good; and that the police had been able to benefit form that change in public attitude.

There's been a few books that delve into the forensic science of Holmes that breaks down what he's doing as well as the good and bad science used.

this is one from 2007:

http://www.amazon.com/gp/aw/d/0470128232/ref=mp_s_a_1_1?qid=1389661999&sr=8-1&pi=SL75

As for Holmes changing forensics and police, yes I think he had a profound effect. Not that it changed over night, but it really pushed the science aspects of evidence gathering, evidence destruction, and the need to prove the perpetrator beyond a "j'accuse" level of proof. I've read of police forces around the world reading the books if not for the "how to" element, but to provide inspiration on how to approach crime and evidence. Right from the first book, Holmes was showcasing just how the police themselves messed up a crime scene and that still goes on to this day, especially in developing countries where the police can be incompetent and even the forensic staff can buy credentials.