Millennius

Millenius was a city located on Marinus.

Law and order
Order was maintained by the Guardian Division, led by a Chief Enquirer and staffed with Guardians. They were based in the Guardian building and were known for being thorough in their investigations. They patrolled the city and rarely had to deal with serious crimes like murder. (TV: The Keys of Marinus)

Trials were held in the Capitol building at the far end of Central Avenue. (PROSE: Doctor Who and the Keys of Marinus) They were overseen by a tribunal of three judges, one being a senior judge, to whom the cases of the prosecution and the defence were put by two Representatives for the Court. The Representatives were able to produce witnesses to support their case.

According to the legal system, a defendant accused of a crime was considered guilty until proven innocent beyond any shadow of a doubt. A defendant found guilty of murder would be sentenced to death in the days following the verdict. One who caused a disturbance in the court could be instantly sent to the glass factories in the desert for one year without trial. (TV: The Keys of Marinus)

History
When the Conscience of Marinus' key micro-circuits were hidden across the planet to keep the Conscience from being abused by Yartek, one of them was taken to Millenius and locked away in a maximum-security vault. Protected by a guard, it could only be accessed after a complete probity search.

Aydan, Kala and Eyesen conspired to steal and sell the micro-circuit, in the course of which Aydan murdered Eprin, who had been sent to collect the circuit by Arbitan, and framed Ian Chesterton. Ian was put on trial, defended by the First Doctor, and was found not guilty after the plot was uncovered. The senior judge allowed the Doctor and his companions to return the circuit to the Great City.

Following the defeat of Yartek and his Voords, Altos and Sabetha decided to return to Millenius. (TV: The Keys of Marinus)