Presumably there was more than the few days that the comic hints at, between the theft and them getting caught, thus the magistrate probably thought they were s

Presumably there was more than the few days that the comic hints at, between the theft and them getting caught, thus the magistrate probably thought they were so terrible at being deceptful or keeping a story straight, that there was no way they'd not have been caught the same day as the theft. Or to put it another way, it was a different, simpler time.