Makkos 1:8-9

Makkos 1:8

Just as the testimony of two witnesses is invalid if one of them is related to the other or to the accused, or if one of them is otherwise ineligible to testify, this is also true of three witnesses (even though the third person’s testimony is completely superfluous anyway). We know that this is true even in the case of a 100 witnesses from the fact that the Torah says “witnesses” (i.e., in any number). Rabbi Yosi said that this is only true in capital cases but when it comes to financial matters, the evidence can be upheld by the remaining witnesses. Rebbi says that it applies to both financial and capital cases if the court charged the witnesses before they testified (officially making them witnesses) but it does not apply if they did not charge the witnesses. If this were not the case, there would be no alternative for two brothers who witnessed a murder (i.e., since they cannot testify together, their testimony must be joined with that of a third person).

Makkos 1:9

If two witnesses saw a crime committed from one window and two other witnesses saw it from a different window and a person in between these windows issued a warning to the offender, then if some of the witnesses can see the others, they are considered one group for the purposes of testimony; if they cannot see one another, they are two groups. Accordingly, if one group is found to be false witnesses, the offender and the false witnesses are executed but the second group is exempt. Rabbi Yosi says that no one is executed without first being warned by his two witnesses, as per Deuteronomy 17:6, “by the mouth of two witnesses.” Another interpretation of “by the mouth of two witnesses” is that the Sanhedrin may not hear testimony through an interpreter.