Prepare the corpse. The victim in this attack can be a real actor or a dummy. Apply fake blood or other types of makeup to duplicate the wounds someone really would receive in this type of attack. For example, if the person was stabbed, apply fake blood to the incision area as well as pour some on the ground around where the body lies. Position the body where you want it to lie in the room.
Plant the murder weapon somewhere in the room if the detectives are supposed to find it. In some cases, the weapon may be obvious, like a bloody knife lying next to the body. In other cases, the killer may have hidden the object somewhere in the room or used a tool that would not commonly be seen as a weapon. For example, if the killer beat the victim with a candlestick, dab some fake blood on one side of the object and plant it somewhere in the room.
Recreate the scene of the crime. If there was a struggle, show signs of one in the room: papers thrown about, broken pictures or furniture that is tipped over. If appropriate, you could include spatters of blood at points of struggle.
Leave trace evidence for your detectives to find. A torn piece of clothing, hair or a footprint are good examples of clues. Leave fingerprints by actually planting your fingers on various objects or simply drawing mock fingerprints on various door handles, envelopes and weapons.
Lay out the equipment for the detectives to use to analyze the scene. Caution tape can be unrolled to contain the crime scene. Use plastic baggies, masking tape and markers to bag-and-tag evidence. If you have access to a fingerprint duster, instruct the students how to dust for fingerprints. Set out a camera so that the participants can take pictures of the body, evidence and crime scene.