Rambam, Hilchos Eidus, Chapter 6: 

Chapter 6: Verifying the authenticity of a document

Halacha 1: Verifying the authenticity of a document

• The verification of the authenticity of a document is only rabbinically required.
• Three people: A tribunal of three is needed to verify the authenticity of a document.
• Ordinary people: Even three ordinary people may serve as judges in the tribunal and they do not have to be experts.
• Nighttime: The authenticity of a document may not be verified at nighttime.

Halacha 2: The ways to verify the authenticity of a document

• There are five methods in how to verify the authenticity of a document:
  • If the judges recognize the signatures.
  • Having the witnesses sign in front of the judges.
  • Having the witnesses who signed testify to their signature in front of the court.
  • If the witnesses cannot come before the court, then having other witnesses testify to their signature.
  • Comparing their signature on the current document to their signature on other documents.

Halacha 3: The documents valid for signature comparison

• When using the last, fifth, method for signature verification is only valid when compared to the following other documents:
  • Two documents regarding real estate ownership in which the owners have already benefited from for three years without any protest.
  • Two Kesuba documents.
  • From another document whose authenticity was challenged and was already verified in court.
• In all the above cases, we do not accept the above documents from the person who seeks to validate the current document as perhaps he has fabricated everything.

Halacha 4: Writing the method in which the document was validated

• It is not necessary for the court who validates the document to write on the document which of the above methods were used for verification, and simply writing that the court validated the document suffices.
• Nonetheless, the custom amongst all courts is to also write the method.

Halacha 5: Trusting another courts validation of a document

• A court never checks into the authenticity of another court’s validation of a document.
• Nonetheless, the witnesses may be checked after.

Halacha 6: If one of the members of the tribunal died before writing the validation statement

• If one of the members of the three-person tribunal died after the verification but prior to writing it into the document, then this should explicitly be written on the document validation statement.

Halacha 7: If one of the members of the tribunal was testified to be invalid prior to writing the validation statement

• If one of the members of the three-person tribunal was testified to be an invalid judge after the verification but prior to writing it into the document, then if new testimony arrives proving that he is valid to be a judge, then he may sign with his other two colleagues if they have not yet signed. If, however, they have already signed, then he may not join them with his signature unless the original invalidation was overturned.

Halacha 8: Details relating to validating the document

• Writing the statement before signing: It is permitted for the judges to write the validation statement prior to actually validating it, so long as they delay signing it until after the validation.
• Reading the document: There is no need for the judges to read the actual document in the process of validating it, and so long as they can verify the witnesses that are signed on it, it is irrelevant as to what is written on the document.