best evidence rule legal definition

The rule that, to prove the contents of a writing, recording, or photograph, the original is required unless it is not available for some reason other than the serious fault of the party trying to prove the contents thereof. If the original is unavailable, the testimony of the person who created the original or the person who read it (if a writing), listened to it (if a recording), or saw it (if a photograph) may testify to its content. However, modern evidentiary rules usually permit the use of mechanical, electronic, or other similar copy instead of the original.