Rambam - 1 Chapter a Day

See the conclusion of the previous chapter for a definition of these terms.

For the identification of the murder weapon is considered an essential element of his testimony.

The fundamental dimension of the testimony is communicated through the chakirot. They provide sufficient basis for hazamah. The other particulars discovered through the bedikot are secondary. Hence as long as there is no contradiction with regard to them, the testimony is allowed to stand. See Sanhedrin 41b.

This applies with regard to laws involving capital punishment. Different Jaws apply with regard to matters of financial law, as stated in Chapter 3, Halachah 3.

Since the witness does not know the fundamental dimensions of the testimony, his testimony is of no consequence, and he is not considered as part of the same group of witnesses as the other two.
Note the Lechem Mishneh and others who question the Rambam’s ruling based on his ruling in Chapter 5, Halachah 3, which states that when one of three witnesses is discovered to be a relative or otherwise disqualified, the entire testimony is nullified. For Sanhedrin 41a, the source for this halachah, considers the two concepts to be interrelated.
The Lechem Mishneh offers a possible resolution, explaining that in Chapter 5, the Rambam is speaking about an instance where the witnesses testified directly after each other. In this halachah, by contrast, there was an interruption between their testimony. Hence, there is the potential to consider each witness as a separate entity.

In this instance, the three witnesses are considered as a single group. And since there is a contradiction in their testimony, it is disqualified, for it is not “precise.”

If, however, there is a contradiction between them with regard to the day of the week, even if there is only a one day difference with regard to the date, their testimony is nullified (Kessef Mishneh).

In order to juxtapose the lunar and solar calendars, an extra day is added to several months. At present, this is done according to a fixed calendar. In the time of the Temple and for several hundred years thereafter, the question of whether or not to add a month was dependent on the Supreme Sanhedrin's acceptance of the testimony of witnesses who claimed to have sighted the moon on the appropriate night. Although this news was spread rather rapidly, it is possible that a person would be uninformed.
Moreover, even in the present era, when we have a fixed calendar, since the amount of days in a month vary from month to month, it is possible that a person might err at the beginning of the month. Hence this law still applies [Shulchan Aruch (Choshen Mishpat 30:7)].

If, however, one witness mentioned the fifteenth and the other, the sixteenth, we still give them the benefit of the doubt (Radbaz).

For a two day error is too great to attribute to the above factor. As mentioned in the previous halachah, by the middle of the month every one already knows when Rosh Chodesh was commemorated. Also. it is very rare that there ;ire two 30 day months one after the other.

I.e., the second hour after sunrise.

Pesachim 12a states that a person will err in a little bit less than two hours. On that basis, the Kessef Mishneh questions the Rambam’s ruling. In resolution, he explains that when the witness states “the second hour,” the possibility is that he meant any time from the beginning of that hour until the end. The same is true with regard to the third hour. Thus there can be up to a two hour discrepancy between the two testimonies.
The commentaries mention that we are speaking about shaot zemaniot, seasonal hours (i.e., one twelfth of the time from sunrise to sunset), for everything is dependent on the position of the sun in the sky. Kin’at Eliyahu raises the question if similar laws apply today when most people use watches or clocks to tell time.

For it is unlikely that people will make an error of more than two hours.

Before sunrise and at sunrise are factors concerning which a person will not err.