When I was DMing I ran a bunch of different kinds of mysteries... Are you looking for a sample structure, ideas to pillage, a generic SC to use wholesale or what? I actually think the way the new red box handles "challenge strategies" is a good starting point , so your strategies might be (1) examine body, (2) study crime scene, (3) talk to witnesses. I think it's more fun for players to piece together a mystery as a logic puzzle than solely rely on rolling dice. But if you make the clues PCs need to solve the logic puzzle dependent on the skill challenge then there's the chance the players won't have the clues they need... Instead I like to break the SC into different parts with conflict encounters between. The encounters provide the pivotal clues to the logic puzzle, while the SC provides other hints about the killer and makes other encounters easier. If you are a rat bastrd DM, you can have failed checks turn up red herrings. Oh and if you're trying to keep it short you might want to avoid in-character talk with NPCs which tends to break away from the SC model.