Makkos 5b quotes R’ Yosi’s opinion that the halacha that an entire group of witnesses becomes disqualified if one member’s testimony is invalid applies only to capital cases but not to monetary cases. Rashi explains the distinction is based on “v’hitzilu ha’eidah’; since the Torah’s command us to try to avoid administering the death penalty if any exculpatory reason can be found, we have a higher standard for acceptable testimony is capital cases.
Tosfos asks: the gemara equates the criteria of eidus between mamonos and nefashos based on the based on the pasuk of “misphat echad y’hiye lachem”; just as relatives cannot testify together in capital cases, they cannot testify together in monetary cases (Sanhedrin 28). If in nefashos cases the entire set of witnesses are rejected where one is proven invalid, why would we not apply the the same criteria for mamonos cases and reject the entire group where one witness is invalid?
Tosfos answers that we cannot equate the criteria. If two witnesses testify in a nefashos case and one is invalidated, the testimony of the single kosher witness is worthless. If two witnesses testify in a mamonos case and one is invalidated, the testimony of the single witness still has worth – a single witness is sufficient to cause the opposing party to be chayav a shevu’a.
Tosfos answer seems only to beg the question – based on the halacha of “mishpat echad”, we should equate the rules completely; a single witness should have validity in both cases or in neither?
R’ Chaim and R’ Shimon Shkop use the chakira mentioned in Friday’s post to explain Tosfos. The halacha of eidus for nefashos works as a unit – each witness individually accomplishes nothing. There is one haggadas eidus which emerges from a set of two witnesses, not two haggados. If one witness is invalid, we don’t have 50% testimony left, we have 0% testimony. However, eidus for mamonos works very differently. Each witness who testifies provides a valid haggadas eidus; e.g. if the debtor is declared to owe $100, it is as if each witness is responsible for $50 of the penalty being assessed. The fact that a single witness can cause a chiyuv shevua proves that the testimony is not judged as a unit, but as two separate composite parts.
When it comes to determining who an acceptable witness is, we reject relatives both by nefashos and mamonos based on mishpat echad. But when it comes to defining what constitutes a unit of haggadas eidus, the halacha of shevu'a proves that the mechanics of the cases are different.