1) I found, bs'd, the inverse question in the Ye'aros Devash of Rav Yehonasan Eibeshitz zt'l (vol. II, Derush #8, p. 185, DH uvi'Yemei Chorpi Hayisi). He discusses a murder which took place in front of Beis Din and was seen clearly by all the members of Beis Din. According to Rav Kahana (end of Sanhedrin 17a), if they will all say that Reuven committed the murder, Reuven will be acquitted by the Beis Din. Rav Yehonasan Eibeschitz writes that if so, one of the judges should say that Reuven did not commit the crime, and as a result the Sanhedrin will be able to put Reuven to death.

(He writes that according to this suggestion, we can understand the Gemara in Sanhedrin 17a that says that a Dayan may be appointed to the Sanhedrin only if he is capable of proving that a Sheretz is Tahor. The Dayan who is able to justify his statement that Reuven was not the murderer -- even though everyone saw that he in fact was -- must have the same intellectual and persuasive qualities as someone who is able to prove that a Sheretz is Tahor. In fact, the reason why we require a Dayan who can prove that a Sheretz is Tahor is precisely so that in the scenario of a murder in front of Beis Din, he will be able to ensure that the murderer is put to death.)

I contend that according to Rav Eibeshitz, the judge is allowed to lie in order for justice to be done. Similarly, in your scenario, the last judge may lie and say that the defendant is guilty, because this is the way that this judge is convinced that justice will be done.

2) One might argue that there is a crucial difference between the scenario described in your question and the scenario of the Ye'aros Devash. In the Ye'aros Devash's scenario, everyone saw clearly that Reuven committed the murder. The only problem is a technical one concerning how to convert that knowledge into a practical conviction through bypassing the din of Rav Kahana in Sanhedrin 17a. In contrast, in your scenario it is the opposite; all the Dayanim with the exception of the last one believe the accused is guilty, so here the last Dayan is trying to take advantage of Rav Kahana's ruling in order to impose his minority opinion and defeat everyone else. It would seem that the last Dayan is using a trick in order to contradict the rule of the Torah that the Halachah always follows the opinion of the majority of judges.

3) However, I want to cite a Halachah in an attempt to prove that if one of the judges is convinced that he is right and the other judges are wrong, he is allowed to use a trick in order that the truth (according to his view) should prevail. The proof starts from the Mishnah in Sanhedrin 40a. In a capital case, even if 22 judges say that he is guilty and one says that he does not know, we add two new Dayanim and now have 24 (and ignore the one who does not know) and follow the majority. The question is: If a Dayan really does know, can he deliberately say that he does not know in order to alter the ruling?

4) The Rambam (Hilchos Sanhedrin 8:2) writes that the concept of adding Dayanim if one of them says he does not know applies also to cases of monetary law, where two say he is innocent and one says he is guilty. Rav Yehonasan Eibeshitz in Urim v'Tumim (12:3, Urim) cites the Shevus Yakov who says that if one of the judges sees that the other two are perverting the Din so that if the lone judge will say the opposite to the two crooked judges the Halachah will anyway follow the two in the majority, it is better for him to say he does not know so that two new judges will be added and justice might prevail.

5) Rav Yehonasan Eibeshitz agrees with the Shevus Yakov and writes that the thinking behind this is consistent with what the Gemara in Yevamos (65b) states, that one may lie in order to promote peace. If one may lie for the sake of peace, one certainly may lie in order to save the life of an innocent accused.

5) I argue, therefore, that according to Rav Eibeschitz, in our scenario, where the last judge is convinced that all the other judges are under the influence of a bribe or some other serious cause of a grave injustice, he may lie and say that the accused is guilty and thereby save his life.

6) I found that the Klausenberger Rebbe zt'l wrote a Teshuvah (in Teshuvas Divrei Yatziv, Choshen Mishpat #4) on the subject of our discussion. The title of the chapter in his Sefer is "Perverting the Din in order to save the oppressed."

Baruch She'Kivanti to the words of the Divrei Yatziv, who cites both the Urim v'Tumim (about the Dayan who knows what the Halachah is but says that he does not know) and the Ye'aros Devash (about saying that the person who murdered inside Beis Din did not in fact murder, in order to avoid a unanimous guilty verdict which will acquit the accused).

The Divrei Yatziv concludes, on the basis of the Ye'aros Devash, that a Dayan may say the Din in an untrue way so that the true Din can come to light. According to this, it seems that in our original question the last Dayan may say the accused is guilty, so that the Din will be proclaimed that he is innocent, where the latter decision is the true one according to the last Dayan.

7) However, an important condition must be added here. It seems clear that the above applies only where one of the judges knows that the other judges are perverting the Din. These are in fact the words of the Shevus Yakov that I cited above: "ha'Dayanim Mekalkelim ha'Din" -- "the judges are corrupting the Din." An example could be where one judge knows that the other judges have received a bribe, or he knows that they are relying on the testimony of a witness whom he knows is lying. In contrast, if no perversion of the Din is being perpetrated, but rather the last judge has a dispute purely in Halachah with the other judges, it seems that he cannot take advantage of the Din of Rav Kahana on 17a, or the Din that if one judge says he does not know, two new judges are added. If the matter involves a balance of judgement, and not simply a case of perverted justice, the judge is not allowed to say untrue things in order to make the ruling conform with his opinion.

Dovid Bloom