Rava qualifies the Din in our Mishnah that renders a hundred witnesses like two, by establishing it where they testified 'Toch K'dei Dibur' - the time it takes to say 'Shalom Aleicha Rebbi (or 'Shalom Alecha Rebbi u'Mori'). Otherwise, each pair is considered a separate entity.

Rav Acha from Difti asked Ravina how a hundred witnesses can possibly testify within such a short space of time. He answered that - as long as each witness begins his testimony 'Toch k'Dei Dibur' of the previous witness, they will combine.

Rav Papa asked Abaye that according to our Mishnah, why does the murdered man not save the murderer from the death-sentence - since, based a. on the principle that 'Every person is his own relative', and b. on the fact that he witnessed the murder, he disqualifies the testimony as a relative (see also Tosfos DH 'Nirva Yatzil') ...

... according to Rebbi Yossi, who maintains that even a witness who does not intend to testify, is considered a witness.

Abaye answered ...

... Rav Papa - that when the Torah declares a murderer Chayav Misah, it is speaking where he murdered him from behind, and the victim did not see him.

... him, when he asked him why the victim of a rape does not save the rapist from the death-sentence - that there too, the Torah is speaking where he raped him from behind, so that the victim did not see the rapist.

Abaye was stymied however, when Rav Papa asked him why the murderer and the rapist do not save themselves from the death-sentence - since they too, are related to themselves, and ought therefore to disqualify all the other witnesses).

Rava answered all the Kashyos in one sweep by quoting the Pasuk "al-Pi Shenayim Eidim O Sheloshah Eidim Yakum Davar" - which indicates that the comparison between two and three witnesses (the basis of the current discussion) is confined to potential witnesses ('Mekaymei Davar'), but does not extend to the litigants.

According to Rebbi, Pasul witnesses only negate the testimony if they are party to the warning. Beis-Din know whether they are or whether they are not - by asking them before they begin to testify whether they originally arrived on the scene intending to testify or just to watch.

Rav Yehudah Amar Shmuel rules like Rebbi Yossi in our Mishnah. Rav Nachman rules - like Rebbi.

Our Mishnah now discusses a case where one pair of Eidim witness a murder from one window, another pair witness it from another window, and a fifth person warns the murderer in the middle. They will combine to form one testimony - provided some of them see each other (even if the two pairs of witnesses see the person who is warning, even though they cannot see each other [See commentaries on the Mishnah]).

The ramifications of this ruling, assuming that ...

... both pairs can see the person who is warning are that - a. if only one pair becomes Zom'min, the Din of Zom'min will not apply (and the other pair remains Kasher), and b. if one of the witnesses turns out to be a relation to one of the litigants or Pasul for some other reason, all four witnesses will be disqualified.

... they cannot see each other are that - each pair is independent of the other.

Rebbi Yossi disagrees with the Tana Kama, in that, based on the Pasuk "al-Pi Shenayim Eidim ... " - he requires the witnesses themselves (exclusively) to issue the warning.

The Chachamim learn from this Pasuk that - the Sanhedrin must hear the testimony directly from the mouths of the witnesses and not from a translator (which is akin to hearing it from a third party who heard it from the witnesses ['Eid mi'Pi Eid]).

Rav Zutra bar Tuvya learns from the continuation of the previous Pasuk in Shoftim "Lo Yumas al-Pi Eid Echad" that Eidus Meyuchedes - where two witnesses who see a murder from two different windows, are unable to see each other, is Pasul.

We cannot take the Pasuk literally to mean that one witness is not believed - because that we already know from the Reisha of the Pasuk, which requires two witnesses.

We cite a Beraisa, which corroborates the ruling of Rav Zutra bar Tuvya, where the Tana adds to the case of Eidus Meyuchedes - a case where two single Eidim witnessed the act from the same window, but one after the other (whose testimony is also Pasul).

Rav Papa asked Abaye why the Tana why the Tana finds it necessary to add that case - because if Eidus Meyuchedes is Pasul where the two witnesses see the whole act, how much more so where they see only half!

To answer the Kashya, Abaye establishes the Beraisa - where the witnesses saw an act of adultery, in which case each Eid witnesses an entire sin (albeit not the same part of the act), which we might have thought is acceptable.

Rava presents a case where Eidus Meyuchedes is Kasher - namely, where the two witnesses are able to see the person who is in the middle, warning, and he is able to see them.

He also validates a warning that is issued by the victim himself - or where it is issued by a demon.

Rav Nachman validates Eidus Meyuchedes by Dinei Mamonos, and he derives his ruling from the Pasuk "Lo Yumas al-Pi Eid Echad" - which implies that the P'sul of Eidus Meyuchedes is confined to Dinei Misah, but not to Dinei Mamonos.

Rav Zutra asks that, based on the Pasuk "ve'Hitzilu ha'Eidah", any leniency that applies to Dinei Mamonos ought certainly to apply to Dinei Nefashos. In that case, why does our Mishnah rule 'Lefichach, im Nimtza's ... Hu ve'Hein Neheragin'. Why does the Tana not rather combine the two pairs of witnesses (even if they could not see the person warning in the middle), to disqualify the testimony and save the lives of all those concerned.

We have no answer to this Kashya.

When, in a case with which Rava was involved, foreign witnesses came before Rava, he used an interpreter. To reconcile this with our Mishnah, which considers this 'Eid mi'Pi Eid' - we explain that Rava understood the witnesses, and he only employed the interpreter to reply to them in their language.

When Ila'a and Tuvya, relations of the guarantor, testified in a case involving a loan, Rav Papa initially thought that - it didn't matter, seeing as they were not related to the creditor or the borrower.

Rav Huna b'rei de'Rav Yehoshua objected however, because - in the event that the borrower would be unable to pay, the creditor would go to the guarantor (rendering him an intrinsic part of the case), in which case, Ila'a and Tuvya were disqualified from testifying.