Talmud for Sanhedrin 4:3
סַנְהֶדְרִין הָיְתָה כַּחֲצִי גֹרֶן עֲגֻלָּה, כְּדֵי שֶׁיְּהוּ רוֹאִין זֶה אֶת זֶה. וּשְׁנֵי סוֹפְרֵי הַדַּיָּנִין עוֹמְדִין לִפְנֵיהֶם, אֶחָד מִיָּמִין וְאֶחָד מִשְּׂמֹאל, וְכוֹתְבִין דִּבְרֵי הַמְזַכִּין וְדִבְרֵי הַמְחַיְּבִין. רַבִּי יְהוּדָה אוֹמֵר, שְׁלֹשָׁה, אֶחָד כּוֹתֵב דִּבְרֵי הַמְזַכִּין, וְאֶחָד כּוֹתֵב דִּבְרֵי הַמְחַיְּבִין, וְהַשְּׁלִישִׁי כוֹתֵב דִּבְרֵי הַמְזַכִּין וְדִבְרֵי הַמְחַיְּבִין:
Sanhedrin sat in a semi-circle, so that they could see each other, [it being written (Songs of Songs 7:3): "Your navel is like the basin of the moon (sahar)": "Your navel is like the basin (agan)" — this is Sanhedrin, which sits in the center of the world (the Temple site) and defends (maginah - similar to "agan") the entire world. And it is like the moon in that it sits in a circle like a half moon. (The Targum of moon is "sihara.") And they do not sit in a full circle because the litigants and the witnesses must come in and speak before all of them.] And two court scribes stood before them, one on the right; the other on the left, and they wrote down the words of the acquitters and the words of the indicters. R. Yehudah says: (There were) three. One wrote the words of the acquitters; another, the words of the indicters; and a third, the words of the acquitters and the words of the indicters, [so that there be two witnesses for the acquitters and two for the indicters. The halachah is not in accordance with R. Yehudah.]