We hosted a murder mystery party this weekend.
My son-in-law put together the party for our daughter's 25th birthday. It was a total surprise for her, and she didn't know anything about it until he handed her an envelope with her character and instructions enclosed.
There were ten people involved. It was a clue type of murder mystery, no scripts. I believe the entire scenario was written by daughter's husband. I played the personal assistant to "Robert Lear", and acted as the hostess of the evening. I was at the house and greeted each guest as they arrived, all at staggered times. Six of the players were the ones that did most of the running around and solving of clues. In addition to the hostess and the six guests, there was also a Mafia boss (my husband) a police lieutenant, and the victim ("Robert Lear").
My son-in-law was worried that the mystery would go quickly, but just the opposite happened. The party started at 6:30pm and didn't rap up until after 10pm. Clues were gone over and characters met and shared info while they enjoyed some appetizers. They then left the house in two cars to follow the clues. When they had the last clue (which led them back to the house with a key to a safe containing the victim's will) the police detective returned, along with the supposedly dead Robert Lear. All ws sorted out and the mystery was solved. We then enjoyed cake and ice cream.
It really was a lot of fun, but I'm also sure it took a lot of planning on the part of our son-in-law. I was surprised at how well everyone remained true to their characters. A few never broke character, whereas some couldn't help but laugh at times.

The funniest part was that some of the guests didn't realize that they'd be leaving the house to find clues and several of them were dressed a bit crazy.
And I think my husband came close to being thrown out of the local mall for loitering. He played a Mafia boss and the guests were to meet him at the food court. Well, it took them longer to get to that particular clue, so my husband had to sit around the food court for close to an hour. He was wearing sunglasses and a hat, but took them off after the security guard circled around twice. He also said he had to keep getting something to eat,and he moved to diffferent tables a few times. Not at all suspicious!
Here a few pics from the

discussing clues and getting to know one another
opening the safe:
reading of the will:
"Lt. Johnstone" and "Robert Lear" appear:
I'm sure your son and his friends would have a lot of fun doing a murder mystery party! Not having a script made everything more spontaneous, but it also probably kept it harder to rap up the party at a certain time. Either senario would be fun, I think!