A Criminal in the Village

There was a village that was controlled by the all powerful Chief. There was a theft in the village which had occurred recently, however no one knew who it was. The police had gathered up 8 suspects and brought them to the Chief. The Chief gave each of them a stick and said, "These are magic sticks. Overnight one stick will grow two inches longer than the rest. The one with the longer stick is the culprit. I want all of you to show up here again tomorrow." The next day, there was one person's stick that was two inches shorter while the other seven were two inches longer. The Chief had the person with the shorter stick arrested. How did he know that he was the culprit?