Clarification: In the first Perek of Pesachim, the Gemara asks why it is not permitted to eat Chametz during the sixth hour. And it answers that during the sixth hour, the sun is in the middle of the sky (and it is easy to confuse before mid-day with after midday).

Question (Part 1): Bearing in mind that one cannot tell the difference between the sixth and the seventh hours, according to Abaye, who says there that in the opinion of R. Yehudah, a person is liable to err up to a half an hour, and we attribute the error to both witnesses, if one of them claims that the crime took place in the fifth hour and the other one says, the seventh hour, why is their testimony nullified?

Question (Part 2): Why do we not assume that the one who said that it took place in the fifth hour, was referring to the end of the fifth hour, whilst the one who said the seventh hour, meant the beginning of the seventh hour, and the time that it really happened was in six and a half hours, so that each witness erred by half an hour, one before the act and the other, after it?

Answer: When we say that in the sixth hour the sun is in the middle of the sky, and that people are prone to err between the beginning of the sixth hour and the seventh, that is with reference specifically to Chametz, which is the responsibility of all the people; but not with regard to Eidus, which is handled by 'Zerizim' (people who are alert, and will not err to that extent).

Explanation #1: Rashi explains that the punishment of Ir ha'Nidachas is death by the sword; and the lashon "Nefesh be'Nefesh" used in connection with Eidim Zomemin implies that the Torah is speaking about a case of murder.

Question #1: The Lashon "Nefesh be'Nefesh" applies equally to any case of Chayvei Misah, which will result in the death sentence of the Eidim should they turn out to be Zomemin?

Question #2: And besides, in the first Perek o Makos, the Gemara learns from "Nefesh be'Nefesh" the principle that Eidim Zomemin are not sentenced to death unless their testimony ended in a final ruling in Beis-Din?

Explanation #2: Therefore Rashi's second explanation is the correct one - that even if the Pasuk is speaking about all Eidim Zomemin, some of which are Chayav Sekilah, seeing as sometimes they are only Chayav Sayaf, the Torah is not so strict as to sentence them to death before those who are Mazim them have been examined.

Clarification: The Gemara does not mean to say that it ought to have written all four, because that would imply four. And even if it would have written 'Darosh Tidrosh ve'Chakarta' or 'Chakor Tachkor ve'Darashta' it would have implied four, seeing as the Torah did not write 'Darosh Darosh' or Tidrosh Tidrosh', (like the Gemara says in Merubeh - 'Let the Torah write 'Himatzei Himatzei' or Timatzei Timatzei'?).

Explanation #1: The Gemara's She'eilah is restricted to a Chaver, according to those who hold that a Chaver requires warning, since a non-Chaver does not require a Pasuk, since Hasra'ah is only needed in order to turn a Shogeg into a Meizid.

Explanation #2: Alternatively, the Gemara's is asking from where we know that the murder must take place within 'Toch K'dei Dibur' of the warning.