1,988. Valid vs. Invalid Witnesses

Hilchos Sotah 1:18

If one valid witness and multiple women or multiple invalid witnesses arrive at the same time, the valid witness testifying that the woman committed adultery and the women or the invalid witnesses testifying that she didn’t, then the woman is made to drink the bitter water. This is because the testimony of one valid witness and that of multiple invalid witnesses are considered equal.

Hilchos Sotah 1:19

If all the witnesses testifying are invalid, then the disposition depends on the majority. For example, if two women testify that the woman in question committed adultery and three others testify that she didn’t, she is made to drink the bitter water. If three women testify that she didn’t commit adultery and four others testify that she did, then she is not made to drink. If an equal number of women testify each way, then she is made to drink.