All three cases are solved by Judge Dee, the district magistrate, detective, prosecutor, judge, and jury all wrapped up into one person. His powers are vast, and some of the things he can do would be manifestly illegal in a Western judicial system - such as grossly intimidating a witness or suspect, up to and including the extraction of a confession by torture. As against that, making a false judgement could be far more perilous to Dee's kind of magistrate than to a modern western one. Exhuming a dead body without proving that the dead person was murdered would be an act of Sacrilege which would the cost the Judge his job (which very nearly happens to Dee in the course of the book). If the judge had sentenced a person to death and the executed person prove afterwards to have been innocent, the Judge would be himself executed - having made an honest mistake would not be a sufficient plea to save him. Should an innocent person die under torture, both the judge ordering the torture and all members of staff administering the torture would suffer the capital punishment - and members of Dee's staff urging him to cease torture when the suspect proves obdurate shows that they are aware of that dire risk to themselves.