Narcotic Drugs and Psychotropic Substances Act, 1985
66. Presumption as to documents in certain cases.
Where any document-
(i) is produced or furnished by any person or has been seized from the custody or control or any person, in either case, under this Act or under any other law, or
(ii) has been received from any place outside India (duly authenticated by such authority or person and in such manner as may be prescribed by the Central Government) in the course of investigation of any offence under this Act alleged to have been committed by a person, and such document is tendered in any prosecution under this Act in evidence against him, or against him and any other person who is tried jointly with him, the court shall-
(a) presume, unless the contrary is proved, that the signature and every other part of such document which purports to be in the handwriting of any particular person or which the court may reasonably assume to have been signed by, or to be in the handwriting of, any particular person, is in that person's handwriting; and in the case of a document executed or attested, that it was executed or attested by the person by whom it purports to have been so executed or attested;
(b) admit the document in evidence, notwithstanding that it is not duly stamped, if such document is otherwise admissible in evidence;
(c) in a case falling under clause (i), also presume, unless the contrary is proved, the truth of the contents of such document.