Presumption as to documents: court may presume truth and handwriting of prosecution-tendered documents unless contrary proved. When a document produced under this Ordinance or any other law, seized from a person's custody or received from abroad is tendered by the prosecution against that person or a jointly tried co-accused, the court shall, unless the contrary is proved by that person, presume the truth of the document's contents and that signatures or handwriting and any execution or attestation are genuine; such documents must be admitted in evidence even if not duly stamped, provided they are otherwise admissible.