29 CFR §18.1004

1. (a)The original is not required, and other evidence of the contents of a writing, recording, or photograph is admissible if:
   1. (1)Originals lost or destroyed. All originals are lost or have been destroyed, unless the proponent lost or destroyed them in bad faith; or
   2. (2)Original not obtainable. No original can be obtained by any available judicial process or procedure; or
   3. (3)Original in possession of opponent. At a time when an original was under the control of the party against whom offered, that party was put on notice, by the pleading or otherwise, that the contents would be a subject of proof at the hearing, and that party does not produce the original at the hearing; or
   4. (4)Collateral matters. The writing, recording, or photograph is not closely related to a controlling issue.
2. (b)[Reserved]