When Chen Xiang served as the magistrate of Pucheng County in Fujian during the Song Dynasty, he once had a group of suspects detained but could not identify the thief among them.
He gathered all the suspects and declared, "There is a temple bell that can detect the guilty party; it is extremely sensitive. Each of you must now touch the bell. If it rings, the one who touched it is the thief." Secretly, he ordered his men to bring the bell, coat it with black ink, and cover it with a cloth. He then instructed the suspects to reach under the cloth and touch the bell one by one.
Afterwards, he examined everyone's palms and interrogated the only person whose hand was not stained with ink. This suspect was indeed the thief. Fearing the bell would ring and expose him, he had not dared to touch it.