RPGs are great. They allow for all sorts of collaborative fiction with all sorts of people playing all sorts of characters. Never in a stage production could I be cast as a … well, as any of the characters I ever play.
But hold on, “all sorts” of fiction? There’s one in particular that has never worked in my experience, and that is the Murder Mystery. It’s incredibly hard to make a murder mystery work in an RPG. If you go the Agatha Christie route, you need to come up with an outlandish murder scenario, an oddball cast of suspects, and then have the players roll well on their perception rolls to spot key details. If you go the Colin Dexter route, you need to make a dense web of relations between a group of reasonably normal people, and have the players suss out a motive by exploring the whole social web.
Either way, you run into a problem of affordances: you know how, in a video game, some doors just are flat panels with no handles? You know that you can’t open them, because they lack a handle and its affordances. In an RPG, affordances are even more obvious, generally: the GM, in describing things, gives you the set of things you might need to know, or to twiddle, or to play with. They can throw red herrings in there, but that just ameliorates the problem—fundamentally, they’ve still taken a number of things and raised them from the background. A part of a mystery is often identifying what information to take out of the background.
Finally, mysteries are troublesome because of their intrinsically solitary method of solving—the information that solves the mystery can come from many sources, but the moment of eureka comes from one mind, and one mind alone. One person synthesizes the information and then Knows How It Happened. Who wants to play Dr. Watson to some other player’s Holmes? To have everything explained, because either they as a player couldn’t put it together, or they as a player didn’t get enough information to put it together because they did not roll well enough on perception rolls? Not I.
So, if you’ve run a successful murer mystery tabletop RPG, please, tell me how.