It depends on the difficulty. Each case consists on a couple of cards that point you to right direction. The first cases are very easy with very few cards, you'll complete them in 10-15 minutes. Super fast. Then the missions become harder and with more cards, you have to go way back to find the offender. I'd say 30-40 minutes for the longer ones.

The game also has a hard variant where you just read the introduction of the mission and deduce everything else by yourself. I really like this variant and it obviously increases the duration of each mission. The game isn't hard but if feels really great to deduce everything correctly!

My one criticism is that the game shines with 2 players at most, maybe 3.