Identity Witness [Identitätszeuge]
This is a person who is in a close relationship to you (for example a relative or spouse) and who can testify and confirm the data. The identity witness needs an official identification with photo [amtlicher Lichtbildausweis].
If you want to validate a public document with a notary, you must likewise prove your identity with an official identification with photo [amtlicher Lichtbildausweis] with your personal signature.
If you are not in possession of such a document of identification, your identity can also be confirmed by two identity witnesses who can prove their own identity.
Federal Chancellery – HELP Editorial Staff