Summary

Yosef Karo Shulchan Aruch — Choshen Mishpat 46

Thus, if a document was produced in court and witnesses come and say this is our handwriting but we never knew of such testimony and we have no recollection that this party borrowed from or sold to the other, the document would not be verified and the witnesses have a status of the deaf until they recall their testimony. Any judge who does not judge accordingly does not know between his right and left when it comes to monetary law.
Source: Wikisource

Yosef Karo Shulchan Aruch — Choshen Mishpat 46

If there are no witnesses that recognize the thief’s signature, he can write his signature and we will verify based on that as was explained above in seif 13. The same is true if the witness became an apostate after signature. He is treated just as if he became a thief.
Paragraph 35- If a witness signed on a document before becoming a party’s son-in-law and then later became his son-in-law, the witness cannot testify on his own handwriting. Others, however, may testify that they recognize his signature, even if they did not see it until after he became the party’s son-in-law.
Source: Wikisource

Yosef Karo Shulchan Aruch — Choshen Mishpat 46

If only one other witness is found with the surviving witness, the surviving witness may write his signature even on pottery in front of witnesses and set it forth in court until his signature is established in the court- all the more so would it be effective if there are witnesses that can verify the surviving witness’ signature- so that the witness will not be need to testify on his signature.
Source: Wikisource

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