How misleading a cursory reading of a passage in the Torah can be is demonstrated by the Sage Ulla as he analyzes for us the passages (Devarim 25:1-3) which form the basis for a main topic of this mesechta.

Two litigants come before the court and are judged, the Torah tells us "and they exonerate the righteous one and convict the sinful one". Should the guilty one be deserving of lashes then the court is instructed to administer them.

Who is doing the exonerating and convicting? A superficial reading would lead us to assume that it is the judges mentioned at the beginning of that passage. And who is the righteous one and who the sinner? Again, a superficial reading would have us identify them as the two litigants mentioned at the outset of the chapter.

This reading, explains Ulla, makes no sense. Lashes apply only because someone is guilty of violating a Torah prohibition. What relationship is there between his guilt and the exoneration of the righteous party?

We are therefore compelled to understand these passages in an entirely different light. It is not the judges who are doing the exonerating and convicting but rather the witnesses who are testifying in regard to a defendants crime. First came false witnesses who incriminated an innocent man with their testimony. Then came other witnesses who completely nullified their testimony by testifying that they were together with them somewhere else at the time of the alleged crime and could not possibly be telling the truth. Since the Torah instructed us to believe this second set of witnesses the result is that the righteous, innocent defendant is exonerated and the false witnesses are convicted.

The standard punishment for witnesses thus exposed as liars is to suffer the penalty they wished to inflict with their testimony (Devarim 19:19). The passages Ulla deals with relate to situations where such tit-for-tat punishment is not applicable because of an exception made by the Torah (such as the two cases mentioned in the very first mishna). In such cases the Torah instructs us to punish the false witnesses with lashes.

Only the testimony of at least two witnesses is sufficient for conviction in the case of a capital crime. In stating this rule the Torah uses the expression "through the mouths of the witnesses" (Devarim 17:6). The mishna states that this teaches us that judges should hear the testimony directly from the witnesses and not through an interpreter.

It is for this very reason that Rabbi Yochanan lists (Mesechta Sanhedrin 17a) among the qualification of a judge that he be "conversant in all 70 languages," to eliminate the need for an interpreter.

Even though the above-mentioned requirement is written in regard to capital cases, it is evident from our gemara that our Sages saw it as something to look for in judges in financial cases as well. The story is told of two foreigners who came before the court of the Sage Rava who appointed an interpreter to assist him in understanding them. How could he do so, comes the challenge, when the mishna states otherwise? The answer given is that Rava understood the language of these foreigners and required the services of the interpreter only in his communication to them. Since this challenge is presented to Rava who was judging a monetary matter it is clear that the requirement of hearing directly from the witnesses applies to such cases as well.

Many commentaries understood that the two foreigners mentioned here were witnesses and therefore assume that there is no source for insisting that the judge hear the claims directly from the mouths of the litigants as well and not through an interpreter. Support for this approach can be seen in the fact that this expression of "mouths" appears in the Torah in regard to witnesses. Rambam (Hilchot Sanhedrin 21:8), however, extends the requirement to understanding the litigants as well. His position is based on his understanding that the two foreigners in the court of Rava were the litigants and not the witnesses as is indicated in the words "they came before Rava," a term applicable to litigants rather than witnesses.

For an explanation of why our courts today do rely on interpreters see Shulchan Aruch Chosen Mishpat 17:6 and the Pitchei Teshuva there.