Where any document—
(i) is produced or furnished by any person or has been seized from the custody or control of any person, in either case, under this Act or under any other law, or
(ii) has been received from any place outside India in the course of investigation of any offence under this Act alleged to have been committed by any person,
and such document is tendered in any prosecution under this Act in evidence against him, or against him and other persons who are 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;
(b) admit the document in evidence, notwithstanding that it is not duly stamped, if such document is otherwise admissible in evidence.
Legal Commentary & Landmark Judgments: Section 66
Section 66 of the Narcotic Drugs and Psychotropic Substances Act, 1985 enacts an extraordinary statutory presumption regarding the admissibility, execution, handwriting, signature, and truth of contents of documents seized from the custody of an accused, produced by him, or received from outside India. Shifting the burden of proof onto the defense once the document's custody or receipt is demonstrated, Section 66 alters standard evidentiary rules under the Indian Evidence Act, 1872 (now Bharatiya Sakshya Adhiniyam, 2023). However, because Section 66 presumptions are rebuttable, they must be applied with constitutional circumspection to protect the right against self-incrimination under Article 20(3) and fair trial guarantees under Article 21.
In defending against seized ledgers, encrypted notes, WhatsApp chats, or financial records relied upon under Section 66: (1) Challenge the foundational custody—if the seizure memo does not establish unbroken chain of custody of the document or digital device, the presumption does not trigger; (2) For digital evidence, enforce Section 65B Evidence Act / Section 63 BSA 2023 certification requirements—Section 66 does not bypass electronic evidence admissibility mandates; (3) Rebut the presumption on a preponderance of probabilities by showing third-party access, absence of handwriting analysis, or alternative legitimate commercial explanations.