Final answer:
Oral testimony to prove the contents of a writing is generally not permitted under the Best Evidence Rule unless certain exceptions apply, such as the original being lost or the testimony being about a collateral matter. Expert testimony may be admissible and credibility can be influenced by expertise consensus and bias.
Step-by-step explanation:
Under the Best Evidence Rule, oral testimony is generally not allowed to prove the contents of a writing. The rule requires the original document to be presented as evidence when the contents of that document are being questioned. However, there are exceptions that allow oral testimony, such as when the original is lost or destroyed, if it cannot be obtained by any available judicial process, when the party against whom the evidence is being presented had control of the original and is at fault for its unavailability, or when the document is not closely related to the controlling issues in the case. It is also allowed if the writing is a collateral matter and not key to the legal question at hand.
Moreover, testimony from experts may be considered when determining the admissibility of evidence. This includes evaluating whether the person supplying the testimony is an expert, if their testimony aligns with the consensus among experts in the field, and whether the individual is perceived to be biased. These factors can influence whether oral testimony is credible and, thus, allowed.
When considering the admissibility of oral testimony under the Best Evidence Rule, it is also relevant to consider the purpose of the document. If the document was written with an intent to persuade or mislead, that might affect the admissibility and weight of oral testimony.