Forensic examine of st certificate

Once you say that you have been convicted of a case of forgery, that implies that the prosecution would have already proved that the document was forged. This is so because the burden lies on the prosecution. How can you prove the charge of forgery without first proving that the document is forged? However, if that was not done, you can always make a request to the appellate court under Section 391 Cr.P.C. for its examination by a forensic expert. Please note that making a request is your right, whether the appellate court will agree or not is the court’s prerogative. But, why to presume in the beginning itself that the appellate court will not agree? Why not try at least if it can help you?