One thing I'm always very willing to admit is that I have very little grasp on how to structure a mystery. One particular problem goes like this: say I'm writing a village and I decide it has a werewolf. So, naturally, along the road to the village I drop a torn-up body for the party to find. If this were Dragon Age, he'd be sparkling faintly, and when clicked on, a sentence like "This man was mauled by something with large claws; some kind of huge predator. But what kind of predator abandons the meat?" appears and then the corpse stops sparkling and the game has very clearly signalled that there's nothing more to do here.
But in a tabletop game, I don't have that kind of visual cue. Players, being the clever indivduals I brought them up to be, will try to extract as much information as possible. "I check for some kind of wallet. Signet ring. Are his feet bloody? Let's get fingerprints. Let's...." You know, the full Fantastic CSI deal. And I'm not sure how to deal with this.
Option 1 is to find a phrasing that doesn't sound too bad that says "You can't learn anything else useful here and I am telling you as a DM that CSI is not the option right now." Invoking DM narrative power like this seems inelegant, and contrary to the sandbox spirit.
Option 1B is to basically do that, except instead of TELLING them that they can't learn anything else, just answer all their questions with "no" or generic responses. "He doesn't have a wallet. He doesn't have a ring. You obtain his fingerprints and file them for later. His feet...." This option seems terrible. The players are no more free than in Option 1, but now they waste a lot of time.
Option 2 is to just accept that throw-aways aren't viable when exposed to player scrutiny. Instead, every corpse should be a treasure trove of information. Give him a signet ring. Give him a wallet. Having accepted that your players will choose to play CSI whenever possible, just run the best game of CSI you can.
Option 3 is something clever that I haven't thought of yet.