Sanhedrin 36 - Description of the Sanhedrin Trying a Capital Case
Three rows of disciples of the sages would sit before them so that if the presiding judges were deadlocked, more judges could be added from these disciples. The disciples sit in the order of eminence. If the judges needed to ordain someone, they would ordain one of the disciples from the first row. One disciple from the second row would move to the first, one from the third would move to the second, and one more person from the scholarly community would be put in the third row.
Art: The Judge And Jury Society In The Cider Cellar by Archibald Henning