4. Compromise one of the alibis/pieces of evidence (usually via your supporting cast)3. Figure out three alibis and/or provide exonerating evidence for all three2. Come up with your suspects - three people with reasons to want him or her deadIf you are thinking of writing your own murder mystery, here's the formula that has worked for me (still in development):1. Start with writing the setting and figure out who will be your victim (usually played by the author)
Casting is often the biggest challenge. You need three people who will do the extra work of being suspects and one person willing to take on the job of solving the murder - the detective. I sometimes ask certain supporting cast members to be "allies" and give them a bit of information that may be helpful in solving the mystery. Duplicating clues (providing the same information in more than one way) will probably speed things along. In my experience, if I think my clues are way too obvious they are probably just right.
A few other thoughts - You'll probably want to have other games/activities going on while the detective figures out the mystery, cause people will get bored. These can be tailored to fit the theme, and can help maintain the fantasy (along with decorations and costumes). Themed food is also fun, but can get labor-intensive. Anyway, hope this helps!