This document discusses and summarizes 5 key cases related to principles for admitting exhibits and secondary evidence: 1. The Supreme Court held that merely marking an exhibit does not dispense with proving the document. 2. Electronically recorded conversations are admissible if relevant and the voice is identified, provided the recording's accuracy is proved and it is not altered. 3. Documents pass through three stages - filing, admission as evidence, and finally being held as proved or disproved after judicial review. 4. Objecting to a document's admissibility is best done at the evidence recording stage so the objecting party can cross-examine on it, otherwise their rights may be denied.