In the case of Sirico v. Cotto (67 Misc.2d 636, 324 N.Y.S.2d 483)), Sirico claimed to have been injured by Cotto and sued for damaged.  At trial, she called her doctor (Wolfson) testify about what he saw in some x-rays he took of Sirico's spine.  However, he did not have the x-rays. The Court found that under FRE 1001(2) (aka the best evidence rule), a party that wishes to admit a document must offer into evidence the original document.  If that document is not available, then the party must present secondary evidence (like a photocopy), along with an explanation of why the original is not available.  In this case, Sirico did not have the original x-rays and had no explanation of what happened to them.  Therefore her secondary evidence was excluded. The Court noted that a "document" is defined as any physical embodiment of information or ideas, including a letter, a contract, a receipt, a book of account, a blueprint, or even an x-ray plate. Btw, even a copy of the x-ray would have been admissible to the same extent as the original, as per FRE 1003. The Advisory Committee Notes to FRE 1002 indicate that, "FRE 703 allows an expert to give an opinion based on matters not in evidence, and the present rule must be read as being limited accordingly in its application." Basically, the expert may be able to give an opinion on otherwise inadmissible evidence if it is reasonable to do so within the field of expertise.