The first permanent corruption court was established in 150 BC in Rome.  It has a civil procedure and senators as jurors.  In 122 BC the court the procedure became criminal and the jurors equities (a class of citizens drawn from the cavalry).  Berry notes that the court became a political battleground between the senators and equities and thus in 81 BC the courts were reformed and senatorial juries were re-established.  During his prosecution of Verres, a corrupt former Governor of Sicily, Cicero dramatically illustrates the influence of these changes in order to appeal to the senatorial jury’s sense of justice and their need for political legitimacy:

I will tell the Roman people how it is that, when juries consisted of equestrians, there was for nearly fifty years not even the least suspicion of a juror ever having accepted a bribe in return for giving a particular verdict; how it is that, once the courts had been transferred to the senatorial order and the Roman people’s control over each one of you had been removed, it was possible Quintus Calidius to declare on his conviction that nat ex-praetor could be convicted honourably for less than three million sesterces … (para 38)

This prompts me to tell you of a remark which I recently made … when the rejection of jurors was being held … I said that I thought that there would come a time when foreign peoples would send delegations to Rome to request that the extortion law and this court be abolished.  For if there were no courts, they believe that each governor would only carry off enough for himself and his children.  With the courts as they are now, on the otehr hand, they reckon that each governor carries away enough for himself, his advocates, his supporters, the president of the court, and the jurors — in other words, an infinite amount. (para 41).

Cicero, In Verrem I in D. H. Berry (tr) Cicero: Political Speeches (OUP, Oxford 2009).