Hello, first of all, don't worry. Based on the facts you described, please make the following suggestions: 1. Court prosecution is a civil dispute. If you normally accept the summons to appear in court, you can apply to the court for handwriting identification of your father's signature on the guarantee document, which can prove your father's innocence. 2. If the court's judicial expertise confirms that the signature is really not made by your father, you can report the case to the public security organ with the court judgment. It should be a criminal offence for the other party to forge your father's signature to defraud the loan. The above is for reference. It is recommended to contact a professional lawyer to participate in the whole process of litigation and safeguard your father's legitimate rights and interests.