in a classic murder mystery, circumstances limit the number of suspects to a handful of people. The killer cannot be someone we've never met before. This generator will establish the crime and characterize the suspects, only one of whom had the motive, means, and opportunity to kill the victim.
Once the set-up is generated, the DM will have to fill in blanks. They may benefit from making a timetable of events surrounding the murder, just as the players will in trying to solve it. An explanation or clue should be designed for every motive, means, or opportunity that seems to be solid when it's not, or vice-versa-- why does it seem other than it is? Over the course of play, revelations regarding these facts should come both through the work of the players and the squabbling interference of the suspects. There should always be a risk that the perpetrator will escape, destroy evidence, or kill again. In fact, each new murder tends to spur the story forward even though it is nominally a failure of the PC investigators.
- If the murderer seems right off the bat to have motive, means, and opportunity, they must be proactive from the onset in throwing off investigators. They should also have a violent back-up plan.
- Other suspects may think they were responsible. They may cover for the murderer, even confessing themselves.
- Lacking means can be more than lacking access to the murder weapon. It can be the lack of a key, failure to produce the language that was heard from outside the room when the murder took place, or lack of knowledge needed to commit the crime.
- Seeming to lack means or opportunity may sometimes mean that while you truly do lack it, you've contrived a workaround or red herring.
- Some "suspects" can be only distant suspects-- children, servants, strangers, and others you might only list for completeness's sake.
- Culprits can learn unlikely things through eavesdropping, blackmail, and snooping.
- You start with one suspect as the culprit. You may end with several.