I think crime fiction writers--the good ones--are adept at getting in touch with their dark sides. It's not important to actually commit the crime, only to imagine it. I doubt, for example, that Thomas Harris ever really ate a census-taker's liver...
Sometimes personal experience can be worse for writing if you stick too closely to, "That's what really happened."
I'm working as a writer on a TV show and one of the executive producers is a former cop - he brings us lots of stories and he's usually most excited by the "way out there," ones which don't often make for very compelling fiction. A once-in-a-lifetime, freak thing is tough to relate to. Sometimes we say we'd like to have flashing on the screen, "this really happened."
On the other hand, when I was 19 I was arrested for a crime I committed and years later I used it as a character's background in my first crime novel, Dirty Sweet. Like Jude says, it wasn't so much the details of the events (the arrest, the police interrogation, the court room stuff) but the emotional stuff. There were other guys involved and they all pretty much continued with crime as a career (most of them had been arrested before this time as well). I admit, I thought about it. That's the part I used in the book, the wondering about what would have happened if I'd continued down that road (and been way cooler than I really am. The guy in my book is cool).
Like everything else in writing it's not about where stuff comes from, it's about what you do with it.