The largest venues in Westcrown are those previously employed for public executions and for gladiatorial combat. The former would give off entirely the wrong impression about what a trial is, so they go with the latter, not that it’s all that much better. They also contemplated the opera house, actually, but decided that ‘fight to the death for the amusement of the masses’, while not ideal for optics, is better than ‘staged performance featuring the death of some participants for the amusement of the rich’, which is how Infernal Chelish operas went.
There is magical sound-baffling so that the crowd’s roars do not particularly inconvenience the judge or the lawyers or the questioning. Her Majesty thought it tasteless to sell tickets, but there are plenty of people selling snacks, and souvenirs, and drink, and pamphlets, and gory trinkets purported to be parts of the bodies of diabolists and traitors. The people of Westcrown have decided to treat this as the ‘public execution’ kind of event even if it’s going to involve less blood and more sermons and the actual execution will (according to the betting markets set up outside the arena) probably not happen until this afternoon, or maybe even tomorrow.