The fundamental reason for this phenomenon is the darkness under feudal autocracy. In the feudal society, they were able to dominate the bureaucracy, lawless and unfair. The cases they handle can be said to be arbitrary, and they can't bear legal sanctions if they have power and influence, and their punishment can go unpunished. This kind of behavior is essentially a power transaction and a proof of political corruption, but it is such a thing that was finally discovered by the Queen Mother.
At the end of Tongzhi, there was a policeman named Hu Ti 'an, ostensibly a policeman, but actually the leader of a criminal group. Once, he took a few people to rob a rich family. I didn't expect this family to be a senior official who retired from Beijing. When the owner found out, he was sure to be arrested. Finally, he escaped when he caught Hu Ti 'an with conclusive evidence, but he could only let his brother pretend to be Hu Ti 'an. He thought he would get out in three to five years, but he didn't expect to be punished. Finally, my brother was acquitted, removed from the post of county magistrate and sent to the frontier. The official in charge of hearing the case was either dismissed or punished.