The theory upon which secondary evidence is made admissible is, that the primary evidence is not within the offerer's power to produce; so the law requires only the reasonable assurance that the better evidence is not suppressed. Should circumstances indicate that the original evidence is withheld by design, secondary evidence cannot be received.

But where the original instrument is lost, and diligent search has been made in the place where it is most likely to be found, or where it has been destroyed, without fault or design by the party offering secondary evidence, or where such original instrument is in the possession of the opposing party and notice has been served upon him to produce it, or where the primary evidence is inaccessible, then upon showing inability to procure the primary evidence, secondary evidence may be received.