Important: The person alleging forgery must complete this form in longhand. I swear or affirm under penalty of perjury the above stated facts are true and correct to the best of my knowledge.This Affidavit is made voluntarily for the purpose of establishing the fact that my signature is a forgery. 7. Do you know who forged your signature? The person alleging forgery must complete this form in longhand. Affidavit of Check Forgery - Complete, print, sign and mail this form to Star One Credit Union per instructions below. Filling out the California Credible Witness Affidavit form requires accuracy and attention to detail.