Anatomical Gift Directive Witnesses, Eligibility
Any competent adult may serve as a subscribing witness, with one exception.  A donor who is physically unable to write his or her signature may ask another person to execution the Anatomical Gift Directive on his or her behalf.

When this is done, the person who writes the donor's signature is not permitted to sign the document as a witness.

See: Witnesses, Generally; Signing By Another Person; Anatomical Gift Directive, Who May Create; Anatomical Gift Directive, Validity; Anatomical Gift Directive, When Effective; Anatomical Gift Directive, Revoking