People have been collecting things for centuries like dolls, stamps, baseball cards, even shrunken heads. Farther down that spectrum lies the more macabre: the belongings of criminals. The marketplace for such commerce is called "murderabilia.” “You find the thing and there's an odd amount of pleasure in getting a bunch of it,” said Ryan Graveface, a collector who doesn’t sell any of it. What's so captivating about the serial killer stuff? It's a question he's often asked.