From Holly Cote @ TC:

Mystery Nights using the District YA Services Mystery Kits

(for info about which kits we own, see the district supplies page)

I've found that the mystery kits are really easy to use, and I more or less follow the instructions; typically you need to create the evidence and plant it in the 3 crime scenes as suggested.  I also throw in related props which sometimes tend to make it trickier, and throw them off track.  But I'm sneaky! Here are some things that have worked well here for running the night, and I understand that you don't have the same style of space, but maybe you can adapt it too.  :)  We suggest having 3 staff members and the event lasts 2 full hours.  

1. Before the teens arrive, set-up 3 separate crime scenes in various parts of the library and block them off with scene tape. Set-up food, radio and all the player supplies (paper, pens, detective sheets) in a neutral zone.  (we use the meeting room)

2. Gather kids in the neutral zone and let them form teams.  We try to have at least 3-4 teams, with the same number of players.  Assign suspect roles if you haven't done this at a YAAB meeting. Sometimes we need to change the genders of the suspects too. (I usually have to reassign some of these at the event anyways because someone has no-showed who signed up at YAAB.) Explain the flow of the event to the players.

3. Read the opening explanation for the scenario, then 1 staff person takes each individual team to the 1st crime scene, while all the others stay in the neutral zone.  Each team has 5 minutes to investigate, take notes etc., then goes back to the neutral zone.

4. Everyone gathers in neutral zone and suspect statements are read/acted out.  If you have costumes/props, this part is more fun.  (This is the advantage to assigning parts at YAAB.)

5. For the remaining 2 crime scenes, we escort the teams through on rotation, so that there are always 2 scenes being examined until all the teams have had their 5 minutes in each area.  Teams which are not investigating are hanging out in the neutral zone. (This is where you need all 3 staff)

6. Once everyone has seen all 3 scenes, we give the teams 15-20 minutes to discuss everything, and answer the Solution Sheet from the kit.  Then each team presents their answers and reasoning to the whole group.  After they have all had a turn, we read the Solution, and give prizes to the winning team members.  Sometimes they have partial answers, and then I choose the team that's closest to the full answer.

We really liked the "Rock n Roll Over Dead" and "Death gets a Red Card" kits.  We've done the "The Pharoah's Curse" and "The Disappearance of Angela Day" which went well also.