Once a person lost something, and though a couple of suspicious people were taken to the local officer, there wasn't one person who would admint guilt. So the officer had a method of finding out the guilty one. In the back he claimed he had a clock that could sense if a thief placed his hand on the clock it would chime.
So he made all of the suspects one by one enter the back room and touch the clock. If you hadn't stolen anything, the clock wouldn't chime. As they came out the officer inspected their hands and finally grabbed one of the people and yelled,
"It was he who stole your thing." The culprit fainted, paralyzed in fear, and everyone was shocked and asked the officer how he knew. The officer with a smile, said that on the top of the clock he painted a layer of ink. The culprit feared touching the clock and therefore had clean hands.
Someone who does bad things often in his/her hearts feel the most guilt. From this guilty feeling arises fear. And fear will lead him to cover his crime. If we can rise up the fear and use it as a decoy then we can reveal the truth out of him.
Zhongguo Gudai Yuyan Gushi