Presumption of authenticity: court treats prosecution tendered documents as genuine unless rebutted, enabling their admission in evidence. Where a document produced, seized or received under the law and tendered by the prosecution is relied upon against the person from whose custody it came or a co-accused, the court shall, unless the contrary is proved by that person, presume the truth of the document's contents and that signatures, handwriting, execution or attestation are genuine; such a document shall be admitted in evidence notwithstanding lack of proper stamping if it is otherwise admissible.