Deuteronomy 19:15

One witness shall not rise up against a man for any iniquity,
or for any sin, in any sin that he sinneth
Whether capital sins, or pecuniary debts; or whatsoever sins a man may be guilty of whether sins against the first or second table of the law, whether greater or lesser sins, whether in moral or civil things; the Jews except only in the case of a woman suspected of adultery and of beheading the heifer:

at the mouth of two witnesses, or at the mouth of three witnesses,
shall the matter be established;
either for acquittance or condemnation; and the witnesses may not, as Jarchi says, write their testimony in a letter, and send it to the sanhedrim, nor may an interpreter stand between the witnesses and the judges; (See Gill on Deuteronomy 17:6).