Hmm, count me as a person who doesn't believe the writing would be that poor. the guard knows there are lie detecting crystals. There's no way you, as a guard, would be able to rob and kill a person you have detained without having to answer some questions first. Any inquisitor with two brain cells to rub together would be able to formulate a question in a manner where it cannot be easily obfuscated by omitting details. Meaning unless absolutely no one else is available at the guard station there's no way he could get away with a robbery.
Of course there's always the chance that he's the only guard actively working at this time, but if he is then it makes even less sense. How does he find time to interrogate a kid wandering into the town while also guarding the gate if he's the only guard. At best he would just turn the kid away and not allow him to enter. Also if the guard gets ambushed by hooligans then there's no backup. That seems like awfully flimsy security. Why even bother having a guard in the first place at that point.
