All these statements are largely anecdotal I believe. There was no public accountability. You have said that the auditors answered only to Napoleon which meant that he decided what cases should be pursued and what suppressed.
If you see my previous posting concerning the Duke of York you will see that in England it was possible for a trial involving a senior establishment figure to be held in public and reported on. When did this ever happen under Napoleon? Don't quote Dupont because he did not have a public, or even legal, trial.