I have to agree with sketchyswirl, there is no point in trying to figure a fraud out yourself when you can just put it in the scanner.
Also i don't know if i did something wrong or if there just isn't much to the game yet, but i found the progression to be very, very slow. The prices of upgrades feel very unbalanced compared to the payout. The next upgrade i can buy currently, costs me $1000 which requires about 10 minutes of playtime and it's not even of any use to me, because all it does is slightly uncrumple tickets, which i can already do myself in just a few clicks.