Rule 903 Subscribing Witness's Testimony

If you sign a document as a witness, you generally do not need to show up in court to prove the document is real. Most of the time, other evidence can be used to confirm that a document is genuine.

The only exception is when a specific law requires a witness to testify. For example, some states have rules about certain legal documents, like wills, that may require a witness to speak in court. If that kind of law applies to your document, then the witness may need to testify.