The best evidence rule means that the best evidence of which the case in its nature is susceptible, must always be produced. It is one of the cardinal rules of the law of evidence that the best evidence in possession of the party must always be given, that is to say, if a fact is to be proved by oral evidence, the evidence must be that of a person who had directly perceived the fact to which he testifies.
Otherwise, it would be impossible to test, by cross examination, the truth of the testimony; and the law rejects the evidence which cannot adequately be tested. Hearsay evidence is not evidence; it is only in exceptional cases that such evidence is admissible.
Similarly, where the transaction sought to be proved is primarily evidenced by a writing, the writing itself must be produced or accounted for. It is only in the absence of best or primary evidence that the Court will accept what is known as secondary evidence. Secondary evidence will never be received until the party tendering it proves that it is out of his power to obtain the best evidence.