Stupidity: Matt told Joey they could not check on the guard in the hole because they had committed the "perfect crime" but could get caught if the guard got out. Matt later told his friend Tom "everything" about stealing from Ms. Dillard. Bragging about what they did is certainly no way to help ensure they would not get caught.
Stupidity: After stealing the candy tin full of money, Joey gave it to Matt. Standing in front of the house, Matt opened the tin to see all the cash ($12,600). Joey asked him if anyone saw him, and Matt replied, "No. Let's go before they do." Instead of "hiding" the candy tin in his backpack, Matt carried the tin out in the open - and soon ran into a man wearing a security guard uniform.