Sources for the central hall of the Basilica Julia:

Pliny The Younger, Letter 6.33
"Not only was the lower room crowded, but the very galleries were lined with men and women, hanging over in their eagerness to hear (which was difficult) and to see (which was easy)."

Pliny V.9 "the jurors had taken their seats"... evidence for wooden benches.

Pliny 6.33 "180 jurors were in the court... a host of advocates appeared on both sides. The benches were infinitely thronged, and the spacious court was encompasses by a circle of people standing several rows deep."

Suet. Caligula (ref. needed) "He even scattered large sums of money among the commons from the roof of the Basilica Julia for several days in succession."

(Author needed) Bk. II.14 "The audience is a low rout of hired mercenaries. In the middle of the courthouse the dole is dealt round to them as if they were in a dining room, and at this price they run from court to court. So cheaply may you buy the title of the most eloquent. Therefore when you happen to pass the courthouse know that he who has the loudest applause is the worst orator!"