What distinguishes opinion testimony from other forms of testimony?

The distinguishing feature of opinion testimony lies in its reliance on the witness's inference and interpretation of facts that are in dispute, rather than stating facts directly. Opinion testimony allows experts or witnesses to provide insights based on their specialized knowledge, experience, or judgment. This form of testimony often serves to clarify complex issues for the court and can be influential in helping to establish or refute claims being made in the case.

In contrast, testimony that is strictly factual is based on personal knowledge and does not include an evaluation or interpretation of the evidence. While the other options touch on aspects related to testimony—such as the legal weight of perjury, the basis of knowledge, and the format of submission—they do not capture the essence of what differentiates opinion testimony from factual testimony. Opinion testimony's unique characteristic is its reliance on subjective interpretation of evidence rather than objective fact.