English Explanation of Mishnah Sanhedrin 5:5

If they find him not guilty, he is discharged, if not, it [the trial] is adjourned till the following day. During this time they [the judges] go about in pairs, practice moderation in food, drink no wine the whole day, and discuss the case throughout the night.
Early next morning they reassemble in court. He who is in favor of acquittal states, ‘I declare him innocent and I stand by my opinion.’ While he who is in favor of condemnation says: ‘I declare him guilty and stand by my opinion.’ One who [previously] argued for conviction may now argue for acquittal, but one who [previously] argued for acquittal may not now argue for conviction. If they have made any mistake, the two judges’ scribes are to remind them.
If they find him not guilty, they discharge him.
If not, they take a vote. If twelve acquit and eleven condemn, he is acquitted. If twelve condemn and eleven acquit, or if eleven condemn and eleven acquit and one says, ‘I do not know,’ or even if twenty-two acquit or condemn and a single one says, ‘I do not know,’ they add to the judges.
Up to what number is the court increased? By twos up to the limit of seventy-one.
If thirty-six acquit and thirty-five condemn, he is acquitted. But if thirty-six condemn and thirty-five acquit, the two sides debate the case together until one of those who condemn agrees with the view of those who are for acquittal.
Our mishnah deals with the end of the trial procedure, before the final verdict is pronounced. Note that the mishnah gives numerous opportunities for a judge who voted for conviction to overturn his ruling and vote for acquittal. The Rabbis were very cautious that an innocent man should not be found guilty.
Our mishnah describes the court’s procedure after an initial vote has been taken. If at any point the defendant is found to be innocent the trial is over and he is dismissed. If after the initial vote he is found to be guilty, the judges adjourn for the day in order to “sleep” on the case. During this time the judges continuously debate the merits of the case, and neither eat a lot nor drink wine.
When they reassemble the next morning each judge is asked again to state his opinion. A judge may change his vote from a vote for conviction to a vote for acquittal, but not vice versa. If they make a mistake and do not remember how they voted the scribes who recorded the previous vote remind them.
Again, after the second vote, if he is found to be innocent he is dismissed. In order to convict they need a majority of two votes. In a court of twenty three, the requisite number for a capital case, a conviction would therefore require thirteen in favor of conviction with only ten opposed. If a judge states that he does not know whether to convict or acquit he is not counted as part of the quorum of judges. Therefore, even if 22 judges either convict or acquit and one states that he doesn’t know, they need to add more judges in order to fill the quorum of twenty three. These judges who are added in are, as we learned in chapter four, mishnah four, moved up from the ranks of the disciples who sit before the judges. They continue to add judges until they reach either a majority of two in favor of conviction or a majority of one in favor of acquittal. The maximum number of judges is 71, which is the number of the Great Sanhedrin. If, even after there are 71 judges there is still a majority of only one in favor of conviction, they keep discussing the merits of the case until one who had voted for conviction changes his mind and votes for acquittal. Note, that one who had already voted for acquittal may not change his mind and vote now for conviction, as we learned in the beginning of the mishnah.