Za-Chary Za-Chary loading
Ever hear of the board game “Clue”? It's a murder mystery board game for ages 8+ that doesn't get into the graphic details of the murder; it just explains who did it, where they did it, and what weapon they used.

I think if you make your murder mystery game similar to Clue, it should be fine for Scratch. Try not to get into the details of the murder.