Make enough slips for each person playing. Try to make them small enough so its difficult to read what is on them from far away. You will need to write a slip for:  “Murderer” “Detective” On the rest of the slips of paper, write “suspect”. Have each player take one. Remind everyone not to reveal who they are going to play in the game.
Cut up slips of paper. Write each role on the slips of paper. Put the slips in a bowl.