Midrash for Sanhedrin 79:10
אם יש ממש בדבריו שומעין לו ואפילו הוא אומר יש לי ללמד על עצמי זכות שומעין לו ובלבד שיש ממש בדבריו
AND [LIKEWISE] EXAMINED. IF THEIR EVIDENCE TALLIES, THEY [THE JUDGES] COMMENCE [THE PROCEEDINGS] IN FAVOUR [OF THE ACCUSED].<span class="x" onmousemove="('comment',' V. supra 32b. ');"><sup>17</sup></span> SHOULD ONE OF THE WITNESSES DECLARE, 'I HAVE SOMETHING TO SAY IN HIS FAVOUR'; OR ONE OF THE DISCIPLES, 'I HAVE AN ARGUMENT IN HIS DISFAVOUR', HE IS SILENCED.<span class="x" onmousemove="('comment',' Cf. supra 34a. Witnesses after having given their testimony, are not allowed to make any further statements, even for acquittal, as they might do so with a view to avoiding any possible charge of collusion arising out of their first evidence. ');"><sup>18</sup></span>