
Our games are created to be VERY is to host. This makes this format easy to pull off. In our games the host duties are as follows:
- Do what needs to be done to set up the murder. This can be nothing or turning out the lights and popping a balloon. Something along these lines. Nothing drastic.
- If there is another murder that happens then the person who commits the murder will come tell the host they did the dirty deed and where the 'body' can be found. This is to ensure a guest doesn't have to lie 'dead' for hours

- You only need a single Inspector to handle evidence presentation and solution reading. Although, I would have an Inspector for each team/group to handle those murders and plots. So you or them decide who is the better at public speaking and drama for the presentation and solution.
This is the extent of your hosting duties as entailed by the game. This makes it easy to run multiple games at one time. For example, say you have 40 people attending. You have a game sized for 12-20 guests. You would print out 2 Guest Lists and then assign your Guests using these. You can label them Group 1 and Group 2 or red and blue or any colors you want. You would print 2 of everything else. The way to be able to tell the difference between the 2 groups would be to use different color name tags or just mark one of the Groups nametags with a highlighter. This way people will know who they have to interact with within their group.
It is best at the beginning of the evening to separate out the 2 groups. Tell them that these will be the people they will need to interact with. Also, let them know that they can talk to people from the other group. Good for plotting, trying to buy information etc... The groups are not actually separated during gameplay. Then you just turn them loose!
Pulling off the murder if there is one that happens, takes a little coordinating. You will need to talk to the people who are playing the characters that are going to be murdered before the party and work this out. When they have accomplished everything they need to do, each one needs to come up to you. When both soon to be murder victims are ready then they would go back and do what they need to be doing when they 'die' If you have to turn out lights and pop a balloon or whatever it is you need to do, you would do so now. In other words, you need to work with the victims to ensure the murders occur simultaneously.
This is pretty much all you have to do to run multiple groups. If you have more questions on this just reply to this post.