A quote from David Fechheimer, found in Sleuthing in San Francisco by Diane Manuel (Stanford Magazine, July–August 2000):
“He’s smart, fun, intellectual, well-educated and eccentric,” says David Fechheimer, a prominent San Francisco sleuth. “I’ve always felt that the people best prepared to be private investigators are former graduate students, who know how to use the library. He also has a balanced family life, which is unusual in the detective business. He’s found that it’s possible to make a good living doing serious work that’s also fun.”
Former grad students, sure. But librarians know even more.