The case can be complicated, or simple—it all depends on where you're sitting.
The guests watching the ceremony sit outside the arena, seeing from beginning to end the "killer" committing the crime and covering his tracks, but those participating in the investigation contest can't see any of that.
Two different perspectives let the guests easily find the high ground; they don't need much brainpower to calmly wait and watch the competition.
"The case is quite interesting, but how do you ensure fairness?"
"Before the contest, everyone involved in designing and setting up the case is kept in a designated area and not allowed any contact with the outside world until the contest ends. So actually, before today, even their own subordinates knew nothing about the cases they designed."
"Then how do you determine who wins?"
"That hourglass over there measures half an hour. Within this time, whoever cracks the case or gets closest to the truth wins."
