Code of Criminal Procedure, 1973–Sec. 311–Application under–Allowed–Document in question is the matriculation certificate of prosecutrix–Determination of date of birth is an important issue as the charge is under POSCO Act–If the same could not be adduced due to mistake, the Court cannot shut down its eyes when the mistake is pointed out during the pendency of trial–Further, the document was filed along with the charge-sheet and its existence was in knowledge of petitioner–It cannot be held that some prejudice would be caused–Held, the application was rightly allowed.