An original document or object offered as proof of a fact in a lawsuit as opposed to a photocopy of, or other substitute for, the item or the testimony of a witness describing it.
Best evidence, also known as primary evidence, usually denotes an original writing, which is considered the most reliable proof of its existence and its contents. If it is available to, and obtainable by, a party, it must be offered into evidence at a trial. Best evidence is distinguishable from secondary evidence, a reproduction of an original or testimony establishing its existence, which will be admissible as proof only if the best evidence cannot be obtained, and ensuring no fault of the party seeking to present it.
The principle that the best available evidence must be presented as proof in a lawsuit is embodied in the best-evidence rule.