Article 12. If requested by the accused, documents which contain the testimony of witnesses or persons other than the accused, or documents which are to be substituted for the abovementioned ones, may not be used as evidence unless the accused is, at the time of the public trial, afforded an opportunity to examine the Persons who have given such testimony or drawn up such documents. However, when it is impossible or extremely difficult to provide such opportunities to the accused, the court may utilize such documents with proper regard for their limitations and the constitutional rights of the accused.