Documentary originals rule is a principle of evidence that in order to prove a writing or a recording or photograph, the party must produce the original writing. If that is unavailable then a mechanical, electronic, or other familiar duplicate, such as a photocopy can be produced. If that is also not available,secondary evidence like the testimony of the drafter or a person who read the document may be admitted. The party required to produce evidence should produce the best evidence available. Hence this rule is also known as the best evidence rule. The rule is codified at Fed. R. Evid. 1001–1004.
The documentary originals rule requires that if the contents of the writing are to be proved, it must be by the production, if possible, of the very writing itself. If the original writing is not produced or its production accounted for, evidence of its contents is not admissible. This rule is applicable to books of account. [Fechtel v. Gatewood, 470 S.W.2d 293 (Tex. Civ. App. Tyler 1971)]
This rule is also known as original-writing rule or original-document rule.