On a summer morning in southern New Jersey, a team of crime-scene investigators gathered around a body lying facedown in a small pool of blood. They surveyed the nearby evidence: a party hat, a stray earring, push pins, cashew nuts.

 "Oooh, cool," said Asia Cadet, a l3-year old investigator, as she crouched low to study the face of the deceased dummy corpse. "His nose is crushed."