Ian Chesterton's trial (The Keys of Marinus)

In Ian Chesterton's trial on Millennius, Marinus, he was charged with the murder of Eprin. The First Doctor acted as attorney on Ian's behalf, with Eyesen acting as prosecutor. The trial was presided over by the senior judge, along with the first and second judges. The trial was made especially difficult for the Doctor, due to Millenius law, which had a policy of a defendant being guilty until proven innocent. (TV: "Sentence of Death")

The trial found that Ian had been wrongly accused of Eprin's murder and that the murderer was in fact Aydan, who had worked in cohort with his wife Kala and the prosecutor Eyesen. The trio had been working to steal one of the five keys to the supercomputer, the Conscience of Marinus. Ian was thus acquitted of any crime. Aydan was murdered by his Kala before he could reveal his accomplices, but she and Eysan were arrested for their crimes - the latter caught red-handed attempting to retrieve the hidden key from within the murder weapon. (TV: "The Keys of Marinus")