about all I could think of would be stuff like stories about the Lindbergh baby. the 50 year rule might be hard.

Definitely. The Stanford White murder, Crippen, Jack the Ripper, the William Desmond Taylor murder, Madeline Smith, Burke and Hare, I could go on and on.

Andrew Lang has a book on historical crimes that's worth checking out (and it's out of copyright, so the kindle version is free) and the wonderful Classic Crimes by William Roughead.

I guess you can see I don't know much about this area.

It's funny, because true crime is probably one of the oldest genres - easily predating the novel, for example. It's one of the things people have always been fascinated by. Also of interest: The Newgate Calendar. 

er . . . . . . .uh . . . . . . . Cain and Abel?

ummmm . . . . . . . . Othello and Desdemona?

Too recent to be "classic", but true---The Devil in the White City, by Erik Larson, about a serial murderer of young women.

Another absolute classic: In Cold Blood by Truman Capote. It's just a year shy of the 50 year cut off.

(we could potentially argue all day about whether Othello and Cain and Abel belong in True Crime or Fiction)

Caviglia:  You'd get no argument whatsoever from me as to them being accounts of  "true" crimes!    It's just that those two references were the first ones that flashed through my mind upon reading "classic crime", followed, of course, by Crime and Punishment, by Fyodor Dostoyevsky.

In 1956, Meyer Levin published Compulsion, a novel based on the still shocking Leopold and Loeb case. Helluva movie too with Orson Wells playing Clarence Darrow.

In 1926, Charles Bolitho published Murder for Profit, which examined the cases of six killers who killed out of greed. Like Classic Crimes by William Roughead, I know it only by high reputation.

Not so many 50-y.o. classics since I don't think the genre as we know it really took off until the late Sixties, early Seventies. I remember reading Emlyn Williams Beyond Belief and Ed Sanders' The Family, when I was a teen in the 70s. That was also a time when The Godfather made the Cosa Nostra popular, so I read Burton B. Turkus' expose of the Mob, Murder, Inc.

There are so many fantastic and grisly true crime books, I'll choose one that made me LOL: Midnight in the Garden of Good and Evil.

& The story of Cain and Abel is paralleled from the earlier Gilgamesh (and Enkidu) epic.